# 78 FR 20718: Endangered and Threatened Wildlife and Plants; Proposed Endangered, Threatened, and Not Warranted Listing Determinations for Six Distinct Population Segments of Scalloped Hammerhead Sharks

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## Section

- **Citation:** 78 FR 20718
- **Heading:** Endangered and Threatened Wildlife and Plants; Proposed Endangered, Threatened, and Not Warranted Listing Determinations for Six Distinct Population Segments of Scalloped Hammerhead Sharks
- **Jurisdiction:** Federal
- **Kind:** Regulations
- **Status:** In force
- **Text as of:** August 14, 2026
- **Source:** Compiled text
- **Location:** Federal Register / Vol. 78 / 78 FR 20718

## Text

DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Parts 223 and 224 [Docket No. 111025652-3245-02] RIN 0648-XA798 Endangered and Threatened Wildlife and Plants; Proposed Endangered, Threatened, and Not Warranted Listing Determinations for Six Distinct Population Segments of Scalloped Hammerhead Sharks AGENCY:
National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

ACTION:
Proposed rule; request for comments.

SUMMARY:
In response to a petition submitted by WildEarth Guardians and Friends of Animals to list the species as threatened or endangered, we, NMFS, have completed a comprehensive status review under the Endangered Species Act (ESA) for the scalloped hammerhead shark ( Sphyrna lewini ). Based on the best scientific and commercial information available, including the status review report (Miller et al., 2013), and other information available since completion of the status review report, we have determined that the species is comprised of six distinct population segments (DPSs) that qualify as species under the ESA: Northwest Atlantic and Gulf of Mexico (NW Atlantic & GOM DPS); Central and Southwest Atlantic (Central & SW Atlantic DPS); Eastern Atlantic DPS; Indo-West Pacific DPS; Central Pacific DPS; and Eastern Pacific DPS. After reviewing the best available scientific and commercial information on the DPSs, we have determined that two DPSs warrant listing as endangered, the Eastern Atlantic and Eastern Pacific DPSs; two DPSs warrant listing as threatened, the Central & SW Atlantic and Indo-West Pacific DPSs; and two DPSs do not warrant listing at this time, the NW Atlantic & GOM DPS and the Central Pacific DPS. Any protective regulations determined to be necessary and advisable for the conservation of the threatened DPSs under ESA section 4(d) would be proposed in a subsequent Federal Register announcement
s; two DPSs warrant listing as threatened, the Central & SW Atlantic and Indo-West Pacific DPSs; and two DPSs do not warrant listing at this time, the NW Atlantic & GOM DPS and the Central Pacific DPS. Any protective regulations determined to be necessary and advisable for the conservation of the threatened DPSs under ESA section 4(d) would be proposed in a subsequent Federal Register announcement. Should the proposed listings be finalized, we would also designate critical habitat for the species, to the maximum extent prudent and determinable. We solicit information to assist these listing determinations, the development of proposed protective regulations, and designation of critical habitat in the event these proposed DPSs are finally listed.

DATES:
Comments on this proposed rule must be received by June 4, 2013. Public hearing requests must be requested by May 20, 2013.

ADDRESSES:
You may submit comments on this document, identified by the code NOAA-NMFS-2011-0261 by any of the following methods:
• Electronic Submissions: Submit all electronic comments via the Federal eRulemaking Portal. Go to www.regulations.gov/#!docketDetail;D=NOAA-NMFS-2011-0261, click the “Comment Now!” icon, complete the required fields, and enter or attach your comments.
• Mail: Submit written comments to Office of Protected Resources, NMFS, 1315 East-West Highway, Silver Spring, MD 20910.
• Fax: 301-713-4060, Attn: Maggie Miller
Instructions: Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on www.regulations.gov without change. All personal identifying information (e.g., name, address, etc.), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible
e end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on www.regulations.gov without change. All personal identifying information (e.g., name, address, etc.), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter “N/A” in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only. The proposed rule and the status review report are also available electronically on the NMFS Web site at http://www.nmfs.noaa.gov/pr/species/fish/scallopedhammerheadshark.htm.
FOR FURTHER INFORMATION CONTACT:
Maggie Miller, NMFS, Office of Protected Resources, (301) 427-8403.

SUPPLEMENTARY INFORMATION:

Background
On August 14, 2011, we received a petition from WildEarth Guardians and Friends of Animals to list the scalloped hammerhead shark ( Sphyrna lewini ) as threatened or endangered under the ESA throughout its entire range, or, as an alternative, to delineate the species into five DPSs (Eastern Central and Southeast Pacific, Eastern Central Atlantic, Northwest and Western Central Atlantic, Southwest Atlantic, and Western Indian Ocean) and list any or all of these DPSs as threatened or endangered. The petitioners also requested that critical habitat be designated for the scalloped hammerhead under the ESA. On November 28, 2011, we published a positive 90-day finding (76 FR 72891), announcing that the petition presented substantial scientific or commercial information indicating the petitioned action of listing the species may be warranted and explained the basis for that finding
endangered. The petitioners also requested that critical habitat be designated for the scalloped hammerhead under the ESA. On November 28, 2011, we published a positive 90-day finding (76 FR 72891), announcing that the petition presented substantial scientific or commercial information indicating the petitioned action of listing the species may be warranted and explained the basis for that finding. We also announced the initiation of a status review of the species, as required by Section 4(b)(3)(a) of the ESA, and requested information to inform the agency's decision on whether the species warranted listing as endangered or threatened under the ESA.
Listing Species Under the Endangered Species Act
We are responsible for determining whether scalloped hammerhead sharks are threatened or endangered under the ESA (16 U.S.C. 1531 et seq. ) To make this determination, we first consider whether a group of organisms constitutes a “species” under Section 3 of the ESA, then whether the status of the species qualifies it for listing as either threatened or endangered. Section 3 of the ESA defines species to include “any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.” On February 7, 1996, NMFS and the U.S. Fish and Wildlife Service (USFWS; together, the Services) adopted a policy describing what constitutes a DPS of a taxonomic species (61 FR 4722). The joint DPS policy identified two elements that must be considered when identifying a DPS: (1) The discreteness of the population segment in relation to the remainder of the species (or subspecies) to which it belongs; and (2) the significance of the population segment to the remainder of the species (or subspecies) to which it belongs. As stated in the joint DPS policy, Congress expressed its expectation that the Services would exercise authority with regard to DPSs sparingly and only when the biological evidence indicates such action is warranted
he remainder of the species (or subspecies) to which it belongs; and (2) the significance of the population segment to the remainder of the species (or subspecies) to which it belongs. As stated in the joint DPS policy, Congress expressed its expectation that the Services would exercise authority with regard to DPSs sparingly and only when the biological evidence indicates such action is warranted.
Section 3 of the ESA defines an endangered species as “any species which is in danger of extinction throughout all or a significant portion of its range” and a threatened species as one “which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.” Thus, Policy on Evaluation of Conservation Efforts When Making Listing Decisions (“PECE”; 68 FR 15100; March 28, 2003). The PECE provides direction for consideration of conservation efforts that have not been implemented, or have been implemented but not yet demonstrated effectiveness.
Status Review
We convened a team of agency scientists to conduct the status review for the species and prepare a report. The status review report of the scalloped hammerhead shark (Miller et al., 2013) compiles the best available information on the status of the scalloped hammerhead shark as required by the ESA, provides information on discreteness and significance of populations and potential DPSs, and assesses the current and future extinction risk for these scalloped hammerhead shark populations, focusing primarily on threats related to the five statutory factors set forth above. We appointed a contractor in the Office of Protected Resources Endangered Species Division to undertake a scientific review of the biology, population status and future outlook for the scalloped hammerhead shark. Next we convened a team of biologists and shark experts (Extinction Risk Analysis (ERA) team) to conduct an extinction risk analysis for the scalloped hammerhead shark populations, using the information in the scientific review
of Protected Resources Endangered Species Division to undertake a scientific review of the biology, population status and future outlook for the scalloped hammerhead shark. Next we convened a team of biologists and shark experts (Extinction Risk Analysis (ERA) team) to conduct an extinction risk analysis for the scalloped hammerhead shark populations, using the information in the scientific review. The ERA team was comprised of a fishery biologist from NMFS Office of Protected Resources, two fishery management specialists from NMFS' Highly Migratory Species Management Division, two research fishery biologists from NMFS' Southeast Fisheries Science Center and Pacific Island Fisheries Science Center, and a fishery biologist contractor with NMFS' Office of Protected Resources, with group expertise in shark biology and ecology, population dynamics, highly migratory species management, and stock assessment science. The status review report presents the ERA team's professional judgment of the extinction risk facing each population but makes no recommendation as to the listing status of each. The status review report is available electronically at http://www.nmfs.noaa.gov/pr/species/fish/scallopedhammerheadshark.htm .
The status review report was peer reviewed by three scientists with scalloped hammerhead shark expertise from academic institutions. The peer reviewers were asked to evaluate the adequacy, appropriateness, and application of data used in the Status Review document as well to evaluate the findings made in the “Assessment of Extinction Risk” section of the report. We subsequently reviewed the status review report, its cited references, and peer review comments, and believe the status review report, upon which this proposed rule is based, provides the best available scientific and commercial information on the scalloped hammerhead shark
Status Review document as well to evaluate the findings made in the “Assessment of Extinction Risk” section of the report. We subsequently reviewed the status review report, its cited references, and peer review comments, and believe the status review report, upon which this proposed rule is based, provides the best available scientific and commercial information on the scalloped hammerhead shark. Much of the information discussed below on scalloped hammerhead shark biology, distribution, abundance, threats, and extinction risk is attributable to the status review report. However, we have independently applied the statutory provisions of the ESA, including evaluation of the factors set forth in Section 4(a)(1)(A)-(E); our regulations regarding listing determinations; and our DPS policy in making the proposed listing determinations.
Life History, Biology, and Status of the Petitioned Species
Taxonomy and Species Description
All hammerhead sharks belong to the family Sphyrnidae and are classified as ground sharks (Order Carcharhiniformes). Most hammerheads belong to the Genus Sphyrna with one exception, the winghead shark ( E. blochii ), which is the sole species in the Genus Eusphyra. The hammerhead sharks are recognized by their laterally expanded head that resembles a hammer, hence the common name “hammerhead.” The scalloped hammerhead shark ( Sphyrna lewini ) is distinguished from other hammerheads by a marked central indentation on the anterior margin of the head, along with two more indentations on each side of this central indentation, giving the head a “scalloped” appearance. It has a broadly arched mouth and the rear margin of the head is slightly swept backward. The dentition of the hammerhead consists of small, narrow, and triangular teeth with smooth edges (often slightly serrated in larger individuals), and is similar in both jaws. The front teeth are erect while subsequent teeth have oblique cusps, and the lower teeth are more erect than the upper teeth (Bester, n.d.)
s a broadly arched mouth and the rear margin of the head is slightly swept backward. The dentition of the hammerhead consists of small, narrow, and triangular teeth with smooth edges (often slightly serrated in larger individuals), and is similar in both jaws. The front teeth are erect while subsequent teeth have oblique cusps, and the lower teeth are more erect than the upper teeth (Bester, n.d.).
The body of the scalloped hammerhead is fusiform, with a large first dorsal fin and low second dorsal and pelvic fins. The first dorsal fin is moderately hooked with its origin over or slightly behind the pectoral fin insertions and the rear tip in front of the pelvic fin origins. The height of the second dorsal fin is less than the anal fin height and has a posterior margin that is approximately twice the height of the fin, with the free rear tip almost reaching the precaudal pit. The pelvic fins have relatively straight rear margins while the anal fin is deeply notched on the posterior margin (Compagno, 1984). The scalloped hammerhead shark generally has a uniform gray, grayish brown, bronze, or olive coloration on top of the body that shades to white on the underside with dusky or black pectoral fin tips.
Current Distribution
The scalloped hammerhead shark can be found in coastal warm temperate and tropical seas worldwide. In the western Atlantic Ocean, the scalloped hammerhead range extends from the northeast coast of the United States (from New Jersey to Florida) to Brazil, including the Gulf of Mexico and Caribbean Sea. In the eastern Atlantic, it can be found from the Mediterranean to Namibia. Populations in the Indian Ocean are found in the following locations: South Africa and the Red Sea to Pakistan, India, and Myanmar, and in the western Pacific the scalloped hammerhead can be found from Japan and China to New Caledonia, including throughout the Philippines, Indonesia, and off Australia. Distribution in the et al., 2009)
n Atlantic, it can be found from the Mediterranean to Namibia. Populations in the Indian Ocean are found in the following locations: South Africa and the Red Sea to Pakistan, India, and Myanmar, and in the western Pacific the scalloped hammerhead can be found from Japan and China to New Caledonia, including throughout the Philippines, Indonesia, and off Australia. Distribution in the et al., 2009). It has also been documented entering enclosed bays and estuaries (Compagno, 1984).
Movement and Habitat Use
Scalloped hammerhead sharks are highly mobile and partly migratory and are likely the most abundant of the hammerhead species (Maguire et al., 2006). These sharks have been observed making primarily short-distance migrations along continental margins as well as between oceanic islands in tropical waters, with tagging studies revealing the tendency for scalloped hammerhead sharks to aggregate around and travel to and from core areas or “hot spots” within locations (Holland et al., 1993; Kohler and Turner, 2001; Duncan and Holland, 2006; Hearn et al., 2010; Bessudo et al., 2011; Diemer et al., 2011). However, scalloped hammerhead sharks are also capable of traveling long distances (1,941 km, Bessudo et al., 2011; 1,671 km, Kohler and Turner, 2001; Hearn et al., 2010), and in many of these tagging studies the sharks were tracked leaving the study area for long periods of time, ranging from 2 weeks to several months (Hearn et al., 2010; Bessudo et al., 2011) to almost a year (324 days) (Duncan and Holland, 2006) before eventually returning, displaying a level of site fidelity to these areas.
Both juveniles and adult scalloped hammerhead sharks occur as solitary individuals, pairs, or in schools. The schooling behavior has been documented during summer migrations off the coast of South Africa as well as in permanent resident populations, like those in the East China Sea (Compagno, 1984)
nd Holland, 2006) before eventually returning, displaying a level of site fidelity to these areas.
Both juveniles and adult scalloped hammerhead sharks occur as solitary individuals, pairs, or in schools. The schooling behavior has been documented during summer migrations off the coast of South Africa as well as in permanent resident populations, like those in the East China Sea (Compagno, 1984). Adult aggregations are most common offshore over seamounts and near islands, especially near the Galapagos, Malpelo, Cocos and Revillagigedo Islands, and within the Gulf of California (Compagno, 1984; CITES, 2010; Hearn et al., 2010; Bessudo et al., 2011). Neonate and juvenile aggregations are more common in nearshore nursery habitats, such as Kāne'ohe Bay in Oahu, Hawaii, coastal waters off Oaxaca, Mexico, and Guam's inner Apra Harbor (Duncan and Holland, 2006; Bejarano-Álvarez et al., 2011). It has been suggested that juveniles inhabit these nursery areas for up to or more than a year, as they provide valuable refuges from predation (Duncan and Holland, 2006).
Diet
The scalloped hammerhead shark is a high trophic level predator (trophic level = 4.1; Cortés, 1999) and opportunistic feeder with a diet that includes a wide variety of teleosts, cephalopods, crustaceans, and rays (Compagno, 1984; Bush, 2003; Júnior et al., 2009; Noriega et al., 2011). In a study on feeding behavior in Kāne'ohe Bay, Bush (2003) found a nocturnal increase in the rate of foraging by juvenile scalloped hammerheads, with sharks consuming a mixture of crustaceans and teleosts. The alpheid and goby species were the most important prey items in their diet. Off the coast of Brazil, immature S. lewini frequently fed on reef and pelagic fish, as well as cephalopod species ( Chiroteuthis sp. and Vampyroteuthis infernalis ) that inhabit deep waters (Júnior et al., 2009). Stomachs of 466 S
enile scalloped hammerheads, with sharks consuming a mixture of crustaceans and teleosts. The alpheid and goby species were the most important prey items in their diet. Off the coast of Brazil, immature S. lewini frequently fed on reef and pelagic fish, as well as cephalopod species ( Chiroteuthis sp. and Vampyroteuthis infernalis ) that inhabit deep waters (Júnior et al., 2009). Stomachs of 466 S. lewini off the coast of Australia revealed the importance of bony fish as a prey item, followed by elasmobranchs, octopus and squid, and baitfish, with a positive correlation between shark length and the proportion of elasmobranchs in stomach contents (Noriega et al., 2011).
Reproduction
The scalloped hammerhead shark is viviparous (i.e., give birth to live young), with a gestation period of 9-12 months (Branstetter, 1987; Stevens and Lyle, 1989), which may be followed by a one-year resting period (Liu and Chen, 1999). Females attain maturity around 200-250 cm total length (TL) while males reach maturity at smaller sizes (range 128-200 cm TL). Estimates of age at maturity vary by region, ranging from 3.8 to 15.2 years, but are likely a result of differences in band interpretations in aging methodology approaches (Piercy et al., 2007). Parturition, however, does not appear to vary by region and may be partially seasonal (Harry et al., 2011), with neonates present year round but with abundance peaking during the spring and summer months (Duncan and Holland, 2006; Adams and Paperno, 2007; Bejarano-Álvarez et al., 2011; Harry et al. 2011; Noriega et al., 2011). Females move inshore to birth, with litter sizes anywhere between 1 and 41 live pups. Off the coast of northeastern Australia, Noriega et al. (2011) found a positive correlation between litter size and female shark length for scalloped hammerheads, as did White et al. (2008) in Indonesian waters. However, off the northeastern coast of Brazil, Hazin et al. (2001) found no such relationship
, 2011). Females move inshore to birth, with litter sizes anywhere between 1 and 41 live pups. Off the coast of northeastern Australia, Noriega et al. (2011) found a positive correlation between litter size and female shark length for scalloped hammerheads, as did White et al. (2008) in Indonesian waters. However, off the northeastern coast of Brazil, Hazin et al. (2001) found no such relationship.
Growth
Total length at birth estimates range from 313 mm TL (Chen et al., 1990) to 570 mm TL (White et al., 2008). Duncan and Holland (2006) calculated an early juvenile growth rate of 9.6 cm per year. Observed maximum sizes for male scalloped hammerheads range from 196-321 cm TL, with the oldest male scalloped hammerhead estimated at 30.5 years (Piercy et al., 2007). Observed maximum sizes for female scalloped hammerheads range from 217-346 cm TL, with the oldest female scalloped hammerhead estimated at 31.5 years (Kotas et al., 2011). Estimates of the von Bertalanffy growth parameters vary by study, location, and sex of the animal, with the following ranges: L∞ = 212 to 519 cm TL, k = 0.05 to 0.25 year−1, t 0 = −3.9 to −0.4 (see Miller et al., 2013).
The life history of the scalloped hammerhead shark, like most elasmobranchs, is characterized as long lived (at least 20-30 years), late maturing, and relatively slow growing (based on Branstetter (1990), where k < 0.1/year indicates slow growth for sharks), which generally contributes to a low intrinsic rate of increase. Using life history parameters from the Atlantic S. lewini populations, estimates of the intrinsic rate of increase (r) for the scalloped hammerhead shark range from 0.028 (Smith et al., 1998) to 0.157 (Cortés et al., 2010). Based on the Food and Agriculture Organization of the United Nations (FAO) productivity indices for exploited fish species (where r < 0.14 is considered low productivity), overall estimates of (r) values for the scalloped hammerhead shark indicate that S
es of the intrinsic rate of increase (r) for the scalloped hammerhead shark range from 0.028 (Smith et al., 1998) to 0.157 (Cortés et al., 2010). Based on the Food and Agriculture Organization of the United Nations (FAO) productivity indices for exploited fish species (where r < 0.14 is considered low productivity), overall estimates of (r) values for the scalloped hammerhead shark indicate that S. lewini populations are generally vulnerable to depletion and may be slow to recover from overexploitation.
Current Status
Scalloped hammerhead sharks can be found worldwide, with no present indication of a range contraction. The oldest living S. lewini populations are found in the central Indo-West Pacific, indicating this region as the origin of the species (Duncan et al., 2006; Daly-Engel et al., 2012). During the late Pleistocene period, S. lewini underwent several dispersal events (Duncan et al., 2006). Following the closing of the Isthmus of Panama, it was suggested that gene flow occurred from west to east, with S. lewini traveling from the Atlantic Ocean into the Indo-Pacific, via southern Africa (Duncan et al., 2006).
Scalloped hammerhead sharks are both targeted and taken as bycatch in many global fisheries, with their fins a primary product for international trade. To a much lesser extent, scalloped hammerhead sharks are also caught for their meat (with Colombia, Kenya, Mexico, Mozambique, Philippines, Seychelles, Spain, Sri Lanka, China (Taiwan), Tanzania, and Uruguay identified as countries that consume hammerhead meat (Vannuccini, 1999; CITES, 2010)). However, given the fact that the meat is essentially unpalatable, due to its high urea concentration, it is thought that current volume of S. lewini traded meat and products is insignificant when compared to the volume of S. lewini fins in international trade (CITES, 2010)
, China (Taiwan), Tanzania, and Uruguay identified as countries that consume hammerhead meat (Vannuccini, 1999; CITES, 2010)). However, given the fact that the meat is essentially unpalatable, due to its high urea concentration, it is thought that current volume of S. lewini traded meat and products is insignificant when compared to the volume of S. lewini fins in international trade (CITES, 2010). Unfortunately, the lack of species-specific reporting in these trade products, as well as the scarcity of information on the fisheries catching scalloped hammerhead sharks prior to the early 1970s, with only occasional mentions in historical records, makes it difficult to assess the current worldwide scalloped hammerhead shark status.
In 2007, the International Union for Conservation of Nature (IUCN) considered the scalloped hammerhead shark to be endangered globally, based on an assessment by Baum et al. (2007) and its own criteria (A2bd and 4bd), and placed the species on its “Red List.” Under criteria A2bd and 4bd, a species may be classified as endangered when its “observed, estimated, inferred or suspected” population size is reduced by 50% or more over the last 10 years, any 10 year time period, or three generation period, whichever is the longer, and where the causes of reduction may not have ceased, be understood, or be reversible based on an index of abundance appropriate to the taxon and/or the actual or potential levels of exploitation. IUCN justification for the categorization includes both species-specific estimates and estimates for the entire hammerhead family that suggest declines in abundance of 50-90 percent over time periods of up to 32 years in various regions of the species' range. The IUCN inferred similar declines in areas where species-specific data are unavailable, but where there is evidence of substantial fishing pressure on the scalloped hammerhead shark
includes both species-specific estimates and estimates for the entire hammerhead family that suggest declines in abundance of 50-90 percent over time periods of up to 32 years in various regions of the species' range. The IUCN inferred similar declines in areas where species-specific data are unavailable, but where there is evidence of substantial fishing pressure on the scalloped hammerhead shark. As a note, the IUCN classification for the scalloped hammerhead shark alone does not provide the rationale for a listing recommendation under the ESA, but the sources of information that the classification is based upon are evaluated in light of the standards on extinction risk and impacts or threats to the species.
Identification of Distinct Population Segments
As described above, the ESA's definition of “species” includes “any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.” The genetic diversity among subpopulations, geographic isolation, and differences in international regulatory mechanisms provide evidence that several populations of scalloped hammerhead sharks meet the DPS Policy criteria. Therefore, prior to evaluating the conservation status for scalloped hammerhead sharks, and in accordance with the joint DPS policy, we considered: (1) The discreteness of any scalloped hammerhead shark population segment in relation to the remainder of the subspecies to which it belongs; and (2) the significance of any scalloped hammerhead shark population segment to the remainder of the subspecies to which it belongs
aluating the conservation status for scalloped hammerhead sharks, and in accordance with the joint DPS policy, we considered: (1) The discreteness of any scalloped hammerhead shark population segment in relation to the remainder of the subspecies to which it belongs; and (2) the significance of any scalloped hammerhead shark population segment to the remainder of the subspecies to which it belongs.
Discreteness
The Services' joint DPS policy states that a population of a vertebrate species may be considered discrete if it satisfies either one of the following conditions: (1) It is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors (quantitative measures of genetic or morphological discontinuity may provide evidence of this separation) or (2) it is delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of Section 4(a)(1)(D) of the ESA. To inform its decisions with respect to possible scalloped hammerhead DPSs, the ERA team mainly relied on genetic data, tagging studies, and evidence of differences in the control of exploitation and management by international governmental bodies.
Although scalloped hammerhead sharks are highly mobile, this species rarely conducts trans-oceanic migrations (Kohler and Turner, 2001; Duncan and Holland, 2006; Duncan et al., 2006; Chapman et al., 2009; Diemer et al., 2011). Female scalloped hammerhead sharks may even display a level of site fidelity for reproduction purposes (Duncan et al., 2006; Chapman et al., 2009) that likely contributes to the apparent genetic discontinuity in the global scalloped hammerhead shark population (Duncan et al., 2006; Chapman et al., 2009; Daly-Engel et al., 2012)
2006; Duncan et al., 2006; Chapman et al., 2009; Diemer et al., 2011). Female scalloped hammerhead sharks may even display a level of site fidelity for reproduction purposes (Duncan et al., 2006; Chapman et al., 2009) that likely contributes to the apparent genetic discontinuity in the global scalloped hammerhead shark population (Duncan et al., 2006; Chapman et al., 2009; Daly-Engel et al., 2012). Genetics analyses for scalloped hammerhead sharks using mitochondrial DNA (mtDNA), which is maternally inherited, and microsatellite loci data, which reflects the genetics of both parents, have consistently shown that scalloped hammerhead subpopulations are genetically diverse and that individual subpopulations can be differentiated, especially those populations separated by ocean basins (Duncan et al., 2006; Chapman et al., 2009; Ovenden et al., 2011; Daly-Engel et al., 2012). Using mtDNA samples, Duncan et al. (2006) discovered no sharing of haplotypes between S. lewini in the Atlantic and those from the Pacific or Indian Ocean, proving genetic isolation by oceanic barriers. Chapman et al. (2009) further substantiated this finding in a subsequent examination of mtDNA from scalloped hammerhead shark fins, confirming the absence of shared haplotypes between S. lewini in the western Atlantic (n = 177) and those found in the Indo-Pacific (n = 275). Using microsatellite loci from 403 S. lewini samples, Daly-Engel et al. (2012) concluded that scalloped hammerhead sharks in the western and eastern Atlantic Ocean were significantly differentiated from other populations in the Pacific and Indian Oceans, suggesting that the male sharks in the Atlantic Ocean rarely mix with scalloped hammerheads found elsewhere in the world.
Atlantic Ocean Population Segments
Further delineation within ocean basins is supported by regional and global genetic studies as well as tagging data
stern and eastern Atlantic Ocean were significantly differentiated from other populations in the Pacific and Indian Oceans, suggesting that the male sharks in the Atlantic Ocean rarely mix with scalloped hammerheads found elsewhere in the world.
Atlantic Ocean Population Segments
Further delineation within ocean basins is supported by regional and global genetic studies as well as tagging data. For example, in the Atlantic, both mitochondrial and microsatellite data indicate genetic discontinuity within this ocean basin, with distinct populations of scalloped hammerhead sharks defined by their respective coasts. Analysis of S. lewini haplotypes from samples taken off West Africa and the East Coast of the United States reveal genetic separation of these two populations and point to missing hypothetical ancestors (Duncan et al., 2006). Using biparentally-inherited DNA, Daly-Engel et al. (2012) also provided evidence of genetic structure across the Atlantic Ocean, with scalloped hammerhead samples from West Africa weakly differentiated from South Carolina samples (F ST = 0.052, 0.05 ≥ P ≥ 0.01) and significantly differentiated from Gulf of Mexico samples (F ST = 0.312, P ≤ 0.001). These studies confirm the genetic isolation of the eastern and western Atlantic scalloped hammerhead populations,
Finer scale delineation within the western Atlantic population is also warranted based on analysis of both maternally and bi-parentally inherited DNA; however, the boundaries of this delineation are unresolved. For example, Chapman et al. (2009) structured the western Atlantic scalloped hammerhead population into three distinct mitochondrial stocks: the northern (U.S. Atlantic and Gulf of Mexico), central (Central American Caribbean), and southern (Brazil) stocks. Daly-Engel et al. (2012), on the other hand, found significant population differentiation in between the Gulf of Mexico and the nearby South Carolina site in the western Atlantic (F ST = 0.201, P < 0.001) using microsatellite fragments
ation into three distinct mitochondrial stocks: the northern (U.S. Atlantic and Gulf of Mexico), central (Central American Caribbean), and southern (Brazil) stocks. Daly-Engel et al. (2012), on the other hand, found significant population differentiation in between the Gulf of Mexico and the nearby South Carolina site in the western Atlantic (F ST = 0.201, P < 0.001) using microsatellite fragments. This finding contrasts with Chapman et al. (2009) who did not find significant population differentiation between S. lewini in the U.S. Atlantic and the Gulf of Mexico, and Duncan et al. (2006) who found a lack of genetic structure along continental margins using mtDNA samples. Thus, although the genetic data support dividing the western Atlantic population into subpopulations, there is disagreement on where the lines should be drawn.
Since differences in genetic composition can sometimes be explained by the behavior of a species, the ERA team examined tagging data to learn more about the movements of the scalloped hammerhead populations along the western Atlantic coast. The available data corroborate the genetic findings that these populations of scalloped hammerhead sharks rarely travel long distances. In fact, the median distance between mark and recapture of 3,278 adult scalloped hammerhead sharks, tagged along the eastern U.S. coast and Gulf of Mexico, was less than 100 km (Kohler and Turner, 2001). In addition, none of these tagged sharks were tracked moving south (Kohler personal communication, 2012), indicating a potential separation of the northwest Atlantic and Gulf of Mexico population from the Central and South American population based on movement behavior (Kohler personal communication, 2012).
To further inform its decisions as to whether there is discreteness amongst the western Atlantic scalloped hammerhead subpopulations, the ERA team looked at possible differences in current conservation status and regulatory mechanisms across international boundaries
Mexico population from the Central and South American population based on movement behavior (Kohler personal communication, 2012).
To further inform its decisions as to whether there is discreteness amongst the western Atlantic scalloped hammerhead subpopulations, the ERA team looked at possible differences in current conservation status and regulatory mechanisms across international boundaries. In the northwest Atlantic and Gulf of Mexico, the United States has implemented strict regulations aimed at controlling the exploitation of the sharks, including the scalloped hammerhead, with the development of fishery management plans (FMPs), requirement for stock assessments, and quota monitoring. On August 29, 2011, NMFS prohibited the taking of scalloped hammerhead sharks by the U.S. commercial highly migratory species (HMS) pelagic longline fishery and recreational fisheries for tunas, swordfish, and billfish in the Atlantic Ocean, including the Caribbean Sea and Gulf of Mexico (76 FR 53652; August 29, 2011). These comprehensive regulatory mechanisms are expected to help protect S. lewini in the northwest Atlantic and Gulf of Mexico. Although the U.S. regulations extend to the U.S. economic exclusive zone (EEZ) in the Caribbean (i.e., surrounding U.S. territories), the vast majority of the Caribbean sea, as well as waters farther south, lack regulatory measures controlling the exploitation of scalloped hammerheads. For example, Brazil, a country that has seen declines of 80 percent or more in catch per unit effort (CPUE) of scalloped hammerheads in various fisheries (FAO, 2010), does not have regulations specific to scalloped hammerhead sharks or quota monitoring of the species. Many countries in Central America are also either lacking protections for shark species or have major problems with enforcement of their respective fishery regulations (Kyne et al., 2012). Thus, the species continues to be heavily fished for by industrial and artisanal fishers in waters off Central and South America
ations specific to scalloped hammerhead sharks or quota monitoring of the species. Many countries in Central America are also either lacking protections for shark species or have major problems with enforcement of their respective fishery regulations (Kyne et al., 2012). Thus, the species continues to be heavily fished for by industrial and artisanal fishers in waters off Central and South America. Due to these differences in control of exploitation and regulatory mechanisms for management and conservation of this species across international boundaries, and coupled with the results from the genetic analyses and tagging studies, the ERA team concluded that the western Atlantic population is, in fact, two discrete subpopulations: the Northwest Atlantic & Gulf of Mexico population and the Central & Southwest Atlantic population. We find both of these population segments satisfy the discreteness criterion under the DPS policy.
Indo-West Pacific Population Segments
Within the Indo-West Pacific region, a lack of genetic structure suggests frequent mixing of scalloped hammerhead populations found in these waters (Daly-Engel et al., 2012). A comparison of microsatellite loci samples from the Indian Ocean, specifically samples from the Seychelles and West Australia, as well as from South Africa and West Australia, indicated either no or weak population differentiation (Daly-Engel et al., 2012). Additionally, there was no evidence of genetic structure between the Pacific and Indian Oceans, as samples from Taiwan, Philippines, and East Australia in the western Pacific showed no population differentiation from samples in the Indian Ocean (F ST = −0.018, P = 0.470) (Daly-Engel et al., 2012). Although these genetic data may imply that males of the species move widely within this region, potentially across ocean basins, tagging studies suggest otherwise. Along the east coast of South Africa, for example, S. lewini moved an average distance of only 147.8 km (data from 641 tagged scalloped hammerheads; Diemer et al., 2011)
Indian Ocean (F ST = −0.018, P = 0.470) (Daly-Engel et al., 2012). Although these genetic data may imply that males of the species move widely within this region, potentially across ocean basins, tagging studies suggest otherwise. Along the east coast of South Africa, for example, S. lewini moved an average distance of only 147.8 km (data from 641 tagged scalloped hammerheads; Diemer et al., 2011). Tagging studies in other regions also suggest limited distance movements, and only along continental margins, coastlines, or between islands with similar oceanographic conditions (Kohler and Turner, 2001; Duncan and Holland, 2006; Bessudo et al., 2011). Thus, it seems more likely that the high connectivity of the habitats found along the Indian and western Pacific coasts has provided a means for this shark population to mix and reproduce without having to traverse deep ocean basins. In fact, along the east coast of Australia, Ovenden et al. (2011) found evidence of only one genetic stock of S. lewini. The samples, spanning almost 2,000 km of coastline on Australia's east coast, showed genetic homogeneity based on eight microsatellite loci and mtDNA markers, suggesting long-shore dispersal and panmixia of scalloped hammerhead sharks (Ovenden et al., 2011). No genetic subdivision existed between Indonesia and the eastern or northern coasts of Australia, suggesting this species may move widely between the connecting habitats of Australia and Indonesia (Ovenden et al., 2009; Ovenden et al., 2011).
Although the aforementioned genetic analyses suggest males of the Indo-West Pacific population appear to make longer distance coastal movements than what the Atlantic subpopulations typically exhibit (Daly-Engel et al., 2012), they have not been observed mixing with the neighboring eastern Atlantic population of sharks. The significant levels of genetic structure between S
Ovenden et al., 2011).
Although the aforementioned genetic analyses suggest males of the Indo-West Pacific population appear to make longer distance coastal movements than what the Atlantic subpopulations typically exhibit (Daly-Engel et al., 2012), they have not been observed mixing with the neighboring eastern Atlantic population of sharks. The significant levels of genetic structure between S. lewini microsatellite samples from South Africa and those from West Africa samples (F ST = 0.07, P ≤ 0.01) corroborate this finding, with the number of migrants moving between these two locations estimated at 0.06 to 0.99 per generation (Daly-Engel et al., 2012). Thus, although connected by a continuous coastline, the genetic data
Pacific Ocean Population Segments
In addition to the Indo-West Pacific population, the ERA team found evidence of two other possible subpopulations of scalloped hammerheads in the Pacific Ocean: those common in the Central Pacific region and those found in the East Pacific region. The Central Pacific subpopulation of scalloped hammerheads appears to be markedly separate from other S. lewini populations within the Pacific Ocean as a consequence of physical and genetic factors. The Central Pacific population is located in the middle of the Pacific Ocean. Their range primarily encompasses the Hawaiian Archipelago, which includes the inhabited main islands in the southeast as well as the largely uninhabited Papahānaumokuākea Marine National Monument that extends from Nihoa to Kure Atoll in the northwest. Johnston Atoll is also included in this population's range due to its proximity to the Hawaiian Archipelago. In order to reach the other neighboring populations in the western and eastern Pacific, the Central Pacific scalloped hammerhead sharks would have to travel over hundreds to thousands of kilometers, overcoming various bathymetric barriers. However, as previously mentioned, tagging studies and mtDNA analyses suggest this species rarely makes long-distance oceanic migrations
he Hawaiian Archipelago. In order to reach the other neighboring populations in the western and eastern Pacific, the Central Pacific scalloped hammerhead sharks would have to travel over hundreds to thousands of kilometers, overcoming various bathymetric barriers. However, as previously mentioned, tagging studies and mtDNA analyses suggest this species rarely makes long-distance oceanic migrations. Instead, the data support the assumption that this species more commonly disperses along continuous coastlines, continental margins, and submarine features, such as chains of seamounts, commonly associated with scalloped hammerhead shark “hotspots” (Holland et al., 1993; Kohler and Turner, 2001; Duncan and Holland, 2006; Hearn et al., 2010; Bessudo et al., 2011; Diemer et al., 2011). This is true even for island populations, with tagged S. lewini individuals frequently migrating to nearby islands and mainlands (Duncan and Holland, 2006; Hearn et al., 2010; Bessudo et al., 2011), but no evidence or data to support oceanic migration behavior.
For example, Bessudo et al. (2011) observed scalloped hammerhead sharks in the Eastern Tropical Pacific (ETP) and noted that although they are capable of covering long distances (i.e., 1941 km), the sharks remain within the area, moving widely around and occasionally between neighboring islands with similar oceanographic conditions. A study conducted in a nursery ground in Hawaii revealed that sharks travelled as far as 5.1 km in the same day, but the mean distance between capture points was only 1.6 km (Duncan and Holland, 2006). Another tagging study in Hawaii indicates that adult males remain “coastal” within the archipelago (Holland personal communication, 2012). The genetic data from scalloped hammerhead populations also supports this theory of limited oceanic dispersal, with significant genetic discontinuity associated with oceanic barriers but less so along continental margins (Duncan et al., 2006; Chapman et al., 2009; Daly-Engel et al., 2012). With regards to the S
t males remain “coastal” within the archipelago (Holland personal communication, 2012). The genetic data from scalloped hammerhead populations also supports this theory of limited oceanic dispersal, with significant genetic discontinuity associated with oceanic barriers but less so along continental margins (Duncan et al., 2006; Chapman et al., 2009; Daly-Engel et al., 2012). With regards to the S. lewini sharks in Central Pacific and Eastern Pacific, both microsatellite loci and mtDNA data indicate significant genetic differentiation between these two populations (Daly-Engel et al., 2011), corroborating the theory of genetic isolation due to biogeographic barriers. Thus, these genetic analyses, coupled with the tagging studies, suggest that the populations of scalloped hammerhead sharks found in the Pacific (i.e. Indo-West Pacific, Central Pacific, and East Pacific subpopulations) rarely conduct open ocean migrations (Kohler and Turner, 2001; Bessudo et al., 2011; Diemer et al., 2011; Holland personal communication, 2012) to mix or reproduce with each other.
Further separating these subpopulations, especially the Central Pacific scalloped hammerhead population from its neighboring western and eastern Pacific populations, are the differences in fisheries regulations across these international boundaries. The Central Pacific currently has many management controls in place that protect important scalloped hammerhead habitats and nursery grounds, as well as fishing regulations that control the exploitation of the species. For example, the fisheries of the Hawaiian Islands are managed by both Federal regulations, such as the Magnuson-Stevens Fishery Conservation and Management Act (MSA), and state regulations aimed at protecting and conserving marine resources. Currently, there are no directed shark fisheries in Hawaii; however, scalloped hammerheads are sometimes caught as bycatch on Hawaiian longline gear
species. For example, the fisheries of the Hawaiian Islands are managed by both Federal regulations, such as the Magnuson-Stevens Fishery Conservation and Management Act (MSA), and state regulations aimed at protecting and conserving marine resources. Currently, there are no directed shark fisheries in Hawaii; however, scalloped hammerheads are sometimes caught as bycatch on Hawaiian longline gear. The Hawaii pelagic longline (PLL) fishery, which operates mainly in the Northern Central Pacific Ocean, is managed through a Fishery Ecosystem Plan (FEP) developed by the Western Pacific Regional Fishery Management Council (WPFMC) and approved by NMFS under the authority of the MSA. In an effort to reduce bycatch in this fishery, a number of gear regulations and fishery management measures have been implemented. For example, a 50-75 nm (92.6-138.9 km) longline fishing buffer zone exists around the Hawaiian Islands, helping to protect scalloped hammerheads from being caught near popular nursery grounds and their coastal adult habitat. Periodic closures and effort limits in the shallow-set sector of this fishery (which has a higher shark catch rate) also helps protect scalloped hammerheads in this fishery.
In addition, mandatory fishery observers have been monitoring both sectors (shallow and deep) of the limited-entry Hawaii-based PLL fishery since 1994, with observer coverage increasing in recent years to provide a more comprehensive bycatch dataset. Shark finning, a practice which involves harvesting sharks, severing their fins and returning their remaining carcasses to the sea, was banned in 2000 for the Hawaii-based longline fishery. Additionally, the U.S. Shark Conservation Act of 2010 requires that sharks lawfully harvested in Federal waters, including those located in the range of this DPS, be landed with their fins naturally attached, and additional legislation aimed at shark finning was enacted in 2010 by the State of Hawaii (State of Hawaii SB2169)
ses to the sea, was banned in 2000 for the Hawaii-based longline fishery. Additionally, the U.S. Shark Conservation Act of 2010 requires that sharks lawfully harvested in Federal waters, including those located in the range of this DPS, be landed with their fins naturally attached, and additional legislation aimed at shark finning was enacted in 2010 by the State of Hawaii (State of Hawaii SB2169). In the neighboring ETP, as well as other islands and countries in the western Pacific, regulatory mechanisms are either missing, inadequate, or weakly enforced, and illegal fishing is widespread. Therefore, it is reasonable to assume that the differences in the control of exploitation and regulatory mechanisms between the Central Pacific and the surrounding countries could influence the conservation status of the scalloped hammerhead population around the Central Pacific region and thus could be considered a discrete population under the DPS policy.
In the eastern Pacific region, results from both microsatellite loci data and mtDNA confirm the genetic isolation of the eastern Pacific S. lewini population from those found in the central and western Pacific, Indian, and Atlantic Oceans (P ≤ 0.001) (Daly-Engel et al., 2012). Nance et al. (2011) suggested that the ETP S. lewini population may actually exist as a series of small and genetically separate populations. This observed low genetic diversity in the eastern Pacific population may indicate peripatric speciation (i.e., formation of new species in isolated peripheral populations that are much smaller than et al., 2006). Interestingly, when compared to samples from the Gulf of Mexico, Daly-Engel et al. (2012) found high levels of allelic differentiation (F ST = 0.519, P ≤ 0.001), suggesting that these two populations have never mixed and thus make up the opposing ends of the S. lewini dispersal range from the Indo-West Pacific
new species in isolated peripheral populations that are much smaller than et al., 2006). Interestingly, when compared to samples from the Gulf of Mexico, Daly-Engel et al. (2012) found high levels of allelic differentiation (F ST = 0.519, P ≤ 0.001), suggesting that these two populations have never mixed and thus make up the opposing ends of the S. lewini dispersal range from the Indo-West Pacific. The genetic differentiation and geographic isolation of the Eastern Pacific population from other scalloped hammerhead populations thus qualify it as a discrete population under the DPS policy.
Based on the above information on scalloped hammerhead population structuring, as well as additional information provided in the status review report, we have concluded that the following six discrete subpopulations of scalloped hammerhead sharks are present in the world: (1) Northwest Atlantic & Gulf of Mexico population segment, (2) Central & Southwest Atlantic population segment, (3) Eastern Atlantic population segment, (4) Indo-West Pacific population segment, (5) Central Pacific population segment, and (6) Eastern Pacific population segment. Each is markedly separate from the other five population segments as a consequence of genetic and/or physical factors, with some population segments also delimited by international governmental boundaries within which differences in control of exploitation, conservation status, or regulatory mechanisms exist that are significant in light of Section 4(a)(1)(D) of the ESA.
Significance
When the discreteness criterion is met for a potential DPS, as it is for the Northwest Atlantic & Gulf of Mexico, Central & Southwest Atlantic, Eastern Atlantic, Indo-West Pacific, Central Pacific, and Eastern Pacific population segments identified above, the second element that must be considered under the DPS policy is significance of each DPS to the taxon as a whole. Significance is evaluated in terms of the importance of the population segment to the overall welfare of the species
lantic & Gulf of Mexico, Central & Southwest Atlantic, Eastern Atlantic, Indo-West Pacific, Central Pacific, and Eastern Pacific population segments identified above, the second element that must be considered under the DPS policy is significance of each DPS to the taxon as a whole. Significance is evaluated in terms of the importance of the population segment to the overall welfare of the species. Some of the considerations that can be used to determine a discrete population segment's significance to the taxon as a whole include: (1) Persistence of the population segment in an unusual or unique ecological setting; (2) evidence that loss of the population segment would result in a significant gap in the range of the taxon; and (3) evidence that the population segment differs markedly from other populations of the species in its genetic characteristics.
Based on the results from the genetic and tagging analyses mentioned previously, we believe that there is evidence that loss of any of the population segments would result in a significant gap in the range of the taxon. For example, the Indo-West Pacific region, which is hypothesized as the center of origin for S. lewini, with the oldest extant scalloped hammerhead species found in this region (Duncan et al., 2006; Daly-Engel et al., 2012), covers a wide swath of the scalloped hammerhead sharks' range (extending from South Africa to Japan, and south to Australia and New Caledonia and neighboring Island countries). However, as Daly-Engel et al. (2012) notes, the migration rate of S. lewini individuals from West Africa into South Africa is very low (0.06 individuals per generation), suggesting that in the case of an Indo-West Pacific extirpation, re-colonization from the Eastern Atlantic to the Western Indian Ocean is very unlikely
n, and south to Australia and New Caledonia and neighboring Island countries). However, as Daly-Engel et al. (2012) notes, the migration rate of S. lewini individuals from West Africa into South Africa is very low (0.06 individuals per generation), suggesting that in the case of an Indo-West Pacific extirpation, re-colonization from the Eastern Atlantic to the Western Indian Ocean is very unlikely. In addition, re-colonization from the Central Pacific DPS would also occur rather slowly (on an evolutionary timescale) as those individuals would have to conduct trans-oceanic migrations, a behavior that has yet to be documented in this species. The Central Pacific region, itself (extending from Kure Atoll to Johnston Atoll, and including the Hawaiian Archipelago), encompasses a vast portion of the scalloped hammerhead sharks' range in the Pacific Ocean and is isolated from the neighboring Indo-West Pacific and eastern Pacific regions by deep expanses of water. Loss of this DPS would result in a decline in the number of suitable and productive nursery habitats and create a significant gap in the range of this taxon across the Pacific Ocean. From an evolutionary standpoint, the Central Pacific population is thought to be the “stepping stone” for colonization to the isolated ETP, as Duncan et al. (2006) observed two shared haplotypes between Hawaii and the otherwise isolated ETP population. In other words, in the case of an ETP extirpation and loss of the Central Pacific population, it would require two separate and rare colonization events to repopulate the ETP population: one for the re-colonization of the Central Pacific and another for the re-colonization of the ETP. Thus, on an evolutionary timescale, loss of the Central Pacific population would result in a significant truncation in the range of the taxon
of an ETP extirpation and loss of the Central Pacific population, it would require two separate and rare colonization events to repopulate the ETP population: one for the re-colonization of the Central Pacific and another for the re-colonization of the ETP. Thus, on an evolutionary timescale, loss of the Central Pacific population would result in a significant truncation in the range of the taxon.
Even those discrete population segments that share a connecting coastline, like the Northwest Atlantic & Gulf of Mexico and Central & Southwest Atlantic population segments, will not likely see individuals re-colonizing the other population segment, given that gene flow is low between these areas and tagging studies show limited distance movements by individuals along the western Atlantic coast. In addition, repopulation by individuals from the eastern Pacific to the western Atlantic, or vice versa, is highly unlikely as these animals would have to migrate through suboptimal oceanographic conditions, such as very cold waters, that are detrimental to this species' survival. Therefore, the display of weak philopatry and constrained migratory movements provides evidence that loss of any of the discrete population segments would result in a significant gap in the range of the scalloped hammerhead shark, negatively impacting the species as a whole.
In summary, the scalloped hammerhead shark population segments considered by the ERA team meet both the discreteness and significance criterion of the DPS policy. We concur with the ERA team's conclusion that there are six scalloped hammerhead shark DPSs, which comprise the global population, and are hereafter referred to as: (1) NW Atlantic & GOM DPS, (2) Central & SW Atlantic DPS, (3) Eastern Atlantic DPS, (4) Indo-West Pacific DPS, (5) Central Pacific DPS, and (6) Eastern Pacific DPS. The boundaries for each of these DPSs, as determined from the DPS analysis, are as follows (see Figure 1):
ion that there are six scalloped hammerhead shark DPSs, which comprise the global population, and are hereafter referred to as: (1) NW Atlantic & GOM DPS, (2) Central & SW Atlantic DPS, (3) Eastern Atlantic DPS, (4) Indo-West Pacific DPS, (5) Central Pacific DPS, and (6) Eastern Pacific DPS. The boundaries for each of these DPSs, as determined from the DPS analysis, are as follows (see Figure 1):
(1) NW Atlantic & GOM DPS—Bounded to the north by 40° N. latitude (lat.), includes all U.S. EEZ waters in the Northwest Atlantic and extends due east along 28° N. lat. off the coast of Florida to 30° W. longitude (long.). In the Gulf of Mexico, the boundary line includes all waters of the Gulf of Mexico, with the eastern portion bounded by the U.S. and Mexico EEZ borders.
(2) Central & SW Atlantic DPS—Bounded to the north by 28° N. lat., to the east by 30° W. long., and to the south by 36° S. lat. All waters of the Caribbean Sea are within this DPS boundary, including the Bahamas' EEZ off the coast of Florida as well as Cuba's EEZ.
(3) Eastern Atlantic DPS—Bounded to the west by 30° W. long., to the north by 40° N. lat., to the south by 36° S. lat., and to the east by 20° E. long., but includes all waters of the Mediterranean Sea.
(4) Indo-West Pacific DPS—Bounded to the south by 36° S. lat., to the west by 15° E. long., and to the north by 40° N. lat. In the east, the boundary line extends from 175° W. long. due south to 10° N. lat., then due east along 10° N.
(5) Central Pacific DPS—Bounded to the north by 40° N lat., to the east by 140° W. long., to the south by 10° N. lat., and to the west by 175° E. long.
ean Sea.
(4) Indo-West Pacific DPS—Bounded to the south by 36° S. lat., to the west by 15° E. long., and to the north by 40° N. lat. In the east, the boundary line extends from 175° W. long. due south to 10° N. lat., then due east along 10° N.
(5) Central Pacific DPS—Bounded to the north by 40° N lat., to the east by 140° W. long., to the south by 10° N. lat., and to the west by 175° E. long.
(6) Eastern Pacific DPS—bounded to the north by 40° N lat. and to the south by 36° S lat. The western boundary line extends from 140° W. long. due south to 10° N., then due west along 10° N. lat. to 140° W. long., then due south to 4° S. lat., then due east along 4° S. lat. to 130° W. long, and then extends due south along 130° W. long.
EP05AP13.001
Assessment of Extinction Risk
The Endangered Species Act (ESA) (Section 3) defines endangered species as “any species which is in danger of extinction throughout all or a significant portion of its range.” Threatened species are “any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.” Neither we nor the USFWS have developed any formal policy guidance about how to interpret the definitions of threatened and endangered. We consider a variety of information and apply professional judgment in evaluating the level of risk faced by a species in deciding whether the species is threatened or endangered. We evaluate both demographic risks, such as low abundance and productivity, and threats to the species including those related to the factors specified by the ESA Section 4(a)(1)(A)-(E).
Methods
As we have explained, we convened an ERA team to evaluate extinction risk to the species. This section discusses the methods used to evaluate threats to each DPS and draw overall extinction risk conclusions for each. As explained further down in this notice, we have separately taken into account other conservation efforts which have the potential to reduce threats identified by the ERA team
hods
As we have explained, we convened an ERA team to evaluate extinction risk to the species. This section discusses the methods used to evaluate threats to each DPS and draw overall extinction risk conclusions for each. As explained further down in this notice, we have separately taken into account other conservation efforts which have the potential to reduce threats identified by the ERA team.
For purposes of the risk assessment, an ERA team comprised of fishery biologists and shark experts was convened to review the best available information on the species and evaluate the overall risk of extinction facing the scalloped hammerhead shark now and in the foreseeable future. The term “foreseeable future” was defined as the timeframe over which threats could be reliably predicted to impact the biological status of the species. After considering the life history of the scalloped hammerhead shark, availability of data, and type of threats, the ERA team decided that the foreseeable future should be defined as approximately 3 generation times for the scalloped hammerhead shark, or 50 years. (A generation time is defined as the time it takes, on average, for a sexually mature female scalloped hammerhead shark to be replaced by offspring with the same spawning capacity). This timeframe (3 generation times) takes into account the time necessary to provide for the conservation and recovery of the species. As a late-maturing species, with slow growth rate and low productivity, it would likely take more than a generation time for any conservative management action to be realized and reflected in population abundance indices (as evidenced by the slow recovery of the NW Atlantic & GOM DPS discussed below).
In addition, the foreseeable future timeframe is also a function of the reliability of available data regarding the identified threats and extends only as far as the data allow for making reasonable predictions about the species' response to those threats
to be realized and reflected in population abundance indices (as evidenced by the slow recovery of the NW Atlantic & GOM DPS discussed below).
In addition, the foreseeable future timeframe is also a function of the reliability of available data regarding the identified threats and extends only as far as the data allow for making reasonable predictions about the species' response to those threats. The ERA team considered extending foreseeable future out to 100 years as well, but after discussion, agreed that
Often the ability to measure or document risk factors is limited, and information is not quantitative or very often lacking altogether. Therefore, in assessing risk, it is important to include both qualitative and quantitative information. In previous NMFS status reviews, Biological Review Teams have used a risk matrix method to organize and summarize the professional judgment of a panel of knowledgeable scientists. This approach is described in detail by Wainright and Kope (1999) and has been used in Pacific salmonid status reviews as well as in the status reviews of many other species (see http://www.nmfs.noaa.gov/pr/species/ for links to these reviews). In the risk matrix approach, the collective condition of individual populations is summarized at the DPS level according to four demographic risk criteria: Abundance, growth rate/productivity, spatial structure/connectivity, and diversity. These viability criteria, outlined in McElhany et al. (2000), reflect concepts that are well-founded in conservation biology and that individually and collectively provide strong indicators of extinction risk.
Using these concepts, the ERA team estimated the extinction risk of each scalloped hammerhead shark DPS based on current and future demographic risks by assigning a risk score to each of the four demographic criteria. The scoring for the risk criteria correspond to the following values: 1—no or very low risk, 2—low risk, 3—moderate risk, 4—high risk, and 5—very high risk
tors of extinction risk.
Using these concepts, the ERA team estimated the extinction risk of each scalloped hammerhead shark DPS based on current and future demographic risks by assigning a risk score to each of the four demographic criteria. The scoring for the risk criteria correspond to the following values: 1—no or very low risk, 2—low risk, 3—moderate risk, 4—high risk, and 5—very high risk. Likewise, the ERA team performed a threats assessment for each DPS by scoring the severity of current threats to the DPS as well as predicting whether the threat will increase, decrease, or stay the same in the foreseeable future. Detailed definitions of these risk scores can be found in the status review report. The scores were tallied (mode, median, range), reviewed by the ERA team, and considered in making the overall risk determination. Although this process helps to integrate and summarize a large amount of diverse information, there is no simple way to translate the risk matrix scores directly into a determination of overall extinction risk. Other descriptive statistics, such as mean, variance, and standard deviation, were not calculated as the ERA team felt these metrics would add artificial precision or accuracy to the results.
Guided by the results from the demographics risk analyses as well as the threats assessment, the ERA team members were asked to use their informed professional judgment to make an overall extinction risk determination for each DPS now and in the foreseeable future. For this analysis, the ERA team again defined five levels of extinction risk: 1—no or very low risk, 2—low risk, 3—moderate risk, 4—high risk, and 5—very high risk: however, the definitions differ slightly from those used in the demographic and threats assessment, and can be found in the status review report. To allow individuals to express uncertainty in determining the overall level of extinction risk facing the species, the ERA team adopted the “likelihood point” (FEMAT) method
very low risk, 2—low risk, 3—moderate risk, 4—high risk, and 5—very high risk: however, the definitions differ slightly from those used in the demographic and threats assessment, and can be found in the status review report. To allow individuals to express uncertainty in determining the overall level of extinction risk facing the species, the ERA team adopted the “likelihood point” (FEMAT) method. This approach has been used in previous NMFS status reviews (e.g., Pacific salmon, Southern Resident killer whale, Puget Sound rockfish, Pacific herring, and black abalone) to structure the team's thinking and express levels of uncertainty when assigning risk categories. For this approach, each team member distributed 10 `likelihood points' among the five levels of risks. The scores were then tallied (mode, median, range) and summarized for each DPS.
Finally, the ERA team did not make recommendations as to whether the species should be listed as threatened or endangered. Rather, the ERA team drew scientific conclusions about the overall risk of extinction faced by each DPS under present conditions and in the foreseeable future based on an evaluation of the species' demographic risks and assessment of threats.
Demographic Data Reviewed by the ERA Team
The amount of available data on scalloped hammerhead shark abundance and trends varies by DPS. The abundance status of the NW Atlantic & GOM DPS is likely the best understood, with over 2 decades of data available from multiple recreational and commercial sources and analyzed in a recent stock assessment by Hayes et al. (2009). Recreational catch data used in this stock assessment were collected by the NMFS Marine Recreational Fishery Statistics Survey, NMFS' Southeast Region Headboat Survey, and the Texas Parks and Wildlife Department Marine Recreational Fishing Survey
with over 2 decades of data available from multiple recreational and commercial sources and analyzed in a recent stock assessment by Hayes et al. (2009). Recreational catch data used in this stock assessment were collected by the NMFS Marine Recreational Fishery Statistics Survey, NMFS' Southeast Region Headboat Survey, and the Texas Parks and Wildlife Department Marine Recreational Fishing Survey. These surveys have been in operation since the early 1970s and provide estimates of total catch data and CPUE data through random-dial telephone surveys, dockside intercept sampling programs, and self-reported logbook or daily catch record surveys. As these surveys do not provide data to estimate catch in biomass, the recreational survey data was only analyzed in terms of numbers of individual sharks. Commercial catch data used in the stock assessment were collected by the NMFS Southeast Fisheries Science Center from the Pelagic Dealer Compliance database and from the Accumulated Landings Systems. Landings weights were converted into catch numbers by dividing the weight by an average weight of the individual animal as reported in the Commercial Shark Fishery Observer Program. In this way, recreational and commercial catch numbers could be directly compared. Discard estimates specifically for scalloped hammerheads are not available before 1987 or after 2001 (due to S. lewini being lumped into a larger dealer report category), so estimates for these years were based on average discards in 1987-1992 and 1993-2001, respectively. Additionally, no catch was assumed to take place prior to 1981 based on insufficient catch data available before that year. This assumption was tested through sensitivity analyses and subsequently accepted by Hayes et al. (2009).
For the stock assessment, indices of relative abundance from fishery-dependent and -independent data were estimated for inclusion in surplus-production models to determine population projections and rebuilding probabilities
to 1981 based on insufficient catch data available before that year. This assumption was tested through sensitivity analyses and subsequently accepted by Hayes et al. (2009).
For the stock assessment, indices of relative abundance from fishery-dependent and -independent data were estimated for inclusion in surplus-production models to determine population projections and rebuilding probabilities. Fishery dependent indices were estimated through CPUE data provided by commercial fishery logbooks and observer programs and standardized according to the Lo method (Lo et al., 1992). Fishery-independent surveys are less biased indices of abundance and were included in the models after standardization. Fishery-independent surveys are assumed to more accurately reflect population abundance due to their standardized sampling methods that are designed not to target specific concentrations of fish. The three fishery-independent surveys that were included in the stock assessment models are: the NMFS Pascagoula longline survey, which uses a standardized, random sampling design stratified by depth and covering the western Gulf of Mexico to North Carolina along the U.S.
In addition to the stock assessment, the ERA team also considered other data sources of abundance estimates. This included a study by Ferretti et al. (2008), which provided historical records of shark catches from the Mediterranean Sea; however, the ERA team had concerns about the species-level identifications in the study. Some CPUE information, providing long-term trends data, was available from beach netting programs off the coasts of South Africa and Australia. The methods and materials from these beach protection programs have largely remained the same over the years, providing a good source of fishery-independent data. In South Africa, the beach protection programs have been in place since the early 1950s, providing catch rates of scalloped hammerhead sharks off various beaches from 1952 to 2003
ng programs off the coasts of South Africa and Australia. The methods and materials from these beach protection programs have largely remained the same over the years, providing a good source of fishery-independent data. In South Africa, the beach protection programs have been in place since the early 1950s, providing catch rates of scalloped hammerhead sharks off various beaches from 1952 to 2003. In Australia, catch data from shark control programs off the coast of Queensland is available from 1986 to 2010. Other data sources for abundance analyses include: estimates of breeding individuals and pups from a scalloped hammerhead nursery ground in Hawaii, diver sighting reports from 1992-2004 in protected waters of the eastern Pacific, and estimates of the rate of population decline in the Gulf of Tehuantepac, Mexico.
Growth and productivity analyses were primarily based on data collected from scalloped hammerhead populations in the Atlantic Ocean as there is some scientific disagreement on the aging methodology used to interpret growth bands in studies on S. lewini from the Pacific Ocean. Scalloped hammerhead sharks develop opaque bands on their vertebrae, which are used to estimate age. For some studies conducted in the eastern and western Pacific, band formation was assumed to occur bi-annually, whereas in the Atlantic, bands were assumed to form annually (see Miller et al., 2013). Although indirect age validation studies for S. lewini are still inconclusive, bomb radiocarbon and calcein methods (direct age validation methods) have been used to validate annual growth bands for two other species of Sphyrna, including the great hammerhead shark ( S. mokarran ) and the bonnethead shark ( S. tiburo ) (Parsons, 1993; Passerotti et al., 2010)
rm annually (see Miller et al., 2013). Although indirect age validation studies for S. lewini are still inconclusive, bomb radiocarbon and calcein methods (direct age validation methods) have been used to validate annual growth bands for two other species of Sphyrna, including the great hammerhead shark ( S. mokarran ) and the bonnethead shark ( S. tiburo ) (Parsons, 1993; Passerotti et al., 2010). Therefore, it seems more likely that the scalloped hammerhead shark undergoes annual band formation, as has been found in other chondrichthyan growth studies (Campana et al., 2002; Okamura and Semba, 2009), and this assumption was used when examining age maturity, growth, and productivity estimates.
For spatial structure/connectivity the ERA team considered the current and historical range of the taxon and the habitat requirements and physical characteristics of the habitat as documented in the scientific literature. With respect to diversity, the ERA team examined the genetic data, which provided estimates of migration rates per generation, and analyzed any potential threats of genetic bottlenecking or other ecological and human-caused factors that could substantially alter the rate of gene flow in the DPS.
Evaluation of Demographic Risks
NW Atlantic & GOM DPS
A recent assessment for the northwest Atlantic and Gulf of Mexico scalloped hammerhead shark stock concluded that the population has declined by over 80 percent since 1981 (Hayes et al., 2009). Other studies have also reported similar decreases in S. lewini populations along the western Atlantic coast. For example, Baum et al. (2003) calculated that the northwest Atlantic population of S. lewini has declined 89 percent since 1986; however, this study is controversial due to its reliance on only pelagic longline logbook data. Off the southeastern U.S. coast, Beerkircher et al. (2002) observed significant declines in nominal CPUE for S. lewini between 1981-1983 (CPUE = 13.37; Berkeley and Campos, 1988) and 1992-2000 (CPUE = 0.48)
alculated that the northwest Atlantic population of S. lewini has declined 89 percent since 1986; however, this study is controversial due to its reliance on only pelagic longline logbook data. Off the southeastern U.S. coast, Beerkircher et al. (2002) observed significant declines in nominal CPUE for S. lewini between 1981-1983 (CPUE = 13.37; Berkeley and Campos, 1988) and 1992-2000 (CPUE = 0.48). On a smaller scale, Myers et al. (2007) documented a 98 percent decline of the S. lewini population off the coast of North Carolina between 1972 and 2003, using standardized CPUE data from shark targeted, fishery-independent surveys. However, the authors also discovered a significant increase in juvenile scalloped hammerheads (instantaneous rate of change = 0.094) from 1989 to 2005. Comparing estimates of population size off the coast of South Carolina, Ulrich (1996) reported a 66 percent decrease between 1983-1984 and 1991-1995. Although these declines in former abundance numbers are significant, the latest stock assessment for this DPS found that population numbers have remained fairly stable since 1995 (Hayes et al., 2009). The stock assessment also predicted a 91 percent probability of the population rebuilding within 30 years under 2005 catch levels. From 2006 to 2010, the U.S. scalloped hammerhead harvest has been below this 2005 catch level. In addition, stronger management measures have been implemented in this fishery, with a scalloped hammerhead shark rebuilding plan expected in 2013, which we believe will substantially contribute to continued increases in abundance and stability of this DPS. As such, the ERA team concluded, and we agree, that the future levels of abundance of the NW Atlantic & GOM DPS alone are unlikely to contribute significantly to its risk of extinction.
The ERA team also noted that sharks, in general, have lower reproductive rates and growth rates compared to bony fishes
will substantially contribute to continued increases in abundance and stability of this DPS. As such, the ERA team concluded, and we agree, that the future levels of abundance of the NW Atlantic & GOM DPS alone are unlikely to contribute significantly to its risk of extinction.
The ERA team also noted that sharks, in general, have lower reproductive rates and growth rates compared to bony fishes. Estimates for the intrinsic rate of increase (r) for scalloped hammerhead sharks are relatively low, ranging from 0.028 to 0.121 (see Miller et al., 2013), suggesting general vulnerability to depletion. But compared to other chondrichthyan species, scalloped hammerhead sharks actually show a moderate rebound potential to exploitation by pelagic longline fisheries common in this DPS (Cortés et al., 2010; ICCAT, 2012).
In addition, the ERA team did not see habitat structure or connectivity as a potential risk to this DPS. Already, an extensive range of essential fish habitat (EFH) has been identified for both juveniles and adults of this DPS. EFH is the habitat necessary for spawning, breeding, feeding, and growth to maturity for a species, and NMFS, the regional fishery management councils, and other Federal agencies work together to minimize threats to these identified EFH areas. The current EFH for this DPS extends from the coastal areas in the Gulf of Mexico from Texas to the southern west coast of Florida and along the Atlantic U.S. southeast coast from Florida up to Long Island, NY. Scalloped hammerhead sharks of all developmental stages have been identified within this EFH range (NMFS, 2006), along the eastern Atlantic and Gulf of Mexico coast, which suggests that habitat connectivity does not appear to be a limiting factor in this DPS's survival. Habitat structure also does not appear to be a threat, with the sharks inhabiting a range of environments with varying complexity (from estuaries to open oceans)
ll developmental stages have been identified within this EFH range (NMFS, 2006), along the eastern Atlantic and Gulf of Mexico coast, which suggests that habitat connectivity does not appear to be a limiting factor in this DPS's survival. Habitat structure also does not appear to be a threat, with the sharks inhabiting a range of environments with varying complexity (from estuaries to open oceans). Because the shark resides in the water column, threats to changes in the physical characteristics of the water column, such as salinity, temperature, and dissolved oxygen, may pose the greatest
Central & SW Atlantic DPS
The ERA team noted that specific abundance numbers for this DPS are unavailable but likely similar to, and probably worse than, those found in the NW Atlantic & GOM DPS, mainly due to the observed intensive fishing pressure on this DPS. In the late 1990s, Amorim et al. (1998) remarked that heavy fishing by longliners led to a decrease in this population off the coast of Brazil. According to the FAO global capture production database, Brazil reported a significant increase in catch of S. lewini during this period, from 30 mt in 1999 to 508 mt by 2002, before decreasing to a low of 87 mt in 2009. Documented heavy inshore fishing has also led to significant declines of adult female S. lewini abundance (up to 90 percent) (CITES, 2010) as well as targeted fishing of and reported decreases in juvenile and neonate scalloped hammerhead populations (Vooren et al., 2005; Kotas et al., 2008). Information from surface longline and bottom gillnet fisheries targeting hammerhead sharks off southern Brazil indicates declines of more than 80 percent in CPUE from 2000 to 2008, with the targeted hammerhead fishery abandoned after 2008 due to the rarity of the species (FAO, 2010). The population abundance in the Caribbean is unknown as catch reporting is sporadic and not normally recorded down to the species level
face longline and bottom gillnet fisheries targeting hammerhead sharks off southern Brazil indicates declines of more than 80 percent in CPUE from 2000 to 2008, with the targeted hammerhead fishery abandoned after 2008 due to the rarity of the species (FAO, 2010). The population abundance in the Caribbean is unknown as catch reporting is sporadic and not normally recorded down to the species level.
However, unlike the NW Atlantic & GOM DPS, exploitation of this DPS continues to go largely unregulated. In Central America, a lack of resources has led to poor enforcement of fishery regulations as well as frequent incidences of illegal fishing (further discussed in the Inadequacy of Existing Regulatory Mechanisms section). In Brazilian waters, there are very few fishery regulations that help protect hammerhead populations. For example, the minimum legal size for a scalloped hammerhead caught in Brazilian waters is 60 cm total length; however, S. lewini pups may range from 38 cm to 55 cm. As the pup sizes are very close to this minimum limit, the legislation is essentially ineffective, and as such, large catches of both juveniles and neonates have been documented from this region (Silveira et al., 2007; Kotas et al., 2008; CITES, 2010). Although Brazil has implemented other measures aimed at protecting species that use inshore areas as nursery grounds, such as by limiting gillnets and closing off certain fishing areas, unlike the management measures in the NW Atlantic & GOM DPS, these regulations are poorly enforced. Because of the lack of enforced fishery regulations, fishers continue to take large numbers of all ages of scalloped hammerhead sharks from inshore and coastal waters of this DPS. These threats, which have contributed to the decline in abundance of this DPS, and will continue to do so into the foreseeable future, are discussed in more detail below
& GOM DPS, these regulations are poorly enforced. Because of the lack of enforced fishery regulations, fishers continue to take large numbers of all ages of scalloped hammerhead sharks from inshore and coastal waters of this DPS. These threats, which have contributed to the decline in abundance of this DPS, and will continue to do so into the foreseeable future, are discussed in more detail below. Given the scalloped hammerhead shark's low intrinsic productivity, the observed downward trends in reported catches and population numbers, and continued threat from bycatch and directed catch in weakly regulated commercial and recreational fisheries, the ERA team concluded, and we agree, that the DPS' current and future levels of abundance are likely to contribute significantly to its risk of extinction.
Eastern Atlantic DPS
Abundance numbers for this DPS are unavailable or unreliable, but population trends likely reflect those found in the NW Atlantic & GOM DPS based on the similar fishing effort of longline fleets in this area (Zeeberg et al. 2006; CITES, 2010). One study that the ERA team reviewed used historical records to estimate declines of > 99.99 percent in both biomass and abundance of scalloped hammerhead sharks over the past 100 years in the Mediterranean Sea (Ferretti et al., 2008). However, the ERA team voiced concerns regarding the species identification in the records, as many of the hammerheads found in the Mediterranean Sea are actually the similarly-looking smooth, not scalloped, hammerhead shark. Recently, Sperone et al. (2012) confirmed the presence of both S. lewini and S. zyganea around southern Italy, providing evidence that the species can still be found in the Mediterranean Sea.
According to data provided to the FAO, S. lewini abundance off the coast of Mauritania has declined by 95 percent since 1999, with evidence of a decrease in average size of the shark since 2006 (FAO, 2013)
Recently, Sperone et al. (2012) confirmed the presence of both S. lewini and S. zyganea around southern Italy, providing evidence that the species can still be found in the Mediterranean Sea.
According to data provided to the FAO, S. lewini abundance off the coast of Mauritania has declined by 95 percent since 1999, with evidence of a decrease in average size of the shark since 2006 (FAO, 2013). Abundance trends from off the coast of other western African countries are not available but likely similar to the situation off Mauritania (FAO, 2013). The status of other stocks from this region may also provide a likely picture of the scalloped hammerhead shark population in this region. According to the latest FAO report on the State of World Fisheries and Aquaculture, most of the pelagic stocks and demersal fish from the Eastern Central Atlantic are considered fully exploited to overexploited (FAO, 2012). In addition, many of the shrimp stocks range between fully and overexploited and the commercially important octopus and cuttlefish stocks in this region are deemed overexploited. Some stocks, such as the white grouper in Senegal and Mauritania, are even considered to be in severe condition. Driving this exploitation is the increasing need for protein resources in this region, both as a trade commodity and as a dietary staple. In fact, many people in Sub-Saharan Africa depend on fish for protein in their diet, with fish accounting for around 22 percent of their protein intake (Heck and Béné, 2005). This proportion increases to over 50 percent in many of the poorer African countries, where other animal protein is scarce, and in West African coastal countries, where fishing has driven the economy for many centuries (Heck and Béné, 2005). For example, fish accounts for 47 percent of protein intake in Senegal, 62 percent in Gambia, and 63 percent in Sierra Leone and Ghana (Heck and Béné, 2005)
. This proportion increases to over 50 percent in many of the poorer African countries, where other animal protein is scarce, and in West African coastal countries, where fishing has driven the economy for many centuries (Heck and Béné, 2005). For example, fish accounts for 47 percent of protein intake in Senegal, 62 percent in Gambia, and 63 percent in Sierra Leone and Ghana (Heck and Béné, 2005). With this reliance on fish stocks for dietary protein as well as a sole source of income for many people in this region, it is not surprising that the FAO reports that “the Eastern Central Atlantic has 43 percent of its assessed stocks fully exploited, 53 percent overexploited and 4 percent non-fully exploited, a situation warranting attention for improvement in management.” (FAO, 2012)
With evidence to suggest that large artisanal fisheries are taking substantial amounts of juvenile scalloped hammerhead sharks from these waters, and reports of fisheries even specializing in catching sphyrnid species (CITES, 2010), it is highly likely that this DPS' status is similar to the status of other fish stocks in this region (i.e., fully to overexploited). Thus, taking into consideration the species' low intrinsic rate of productivity, the largely unregulated catch of the species off West Africa with indications of abundance declines and possible size truncation, threats from overexploitation and poor management,
Indo-West Pacific DPS
Beach protection programs in the Indo-West Pacific region have provided valuable fishery-independent data that reveal drastic declines in this scalloped hammerhead shark population since the early 1950s. Specifically, declines of 99 percent, 86 percent, and 64 percent have been estimated for S. lewini from catch rates in shark nets deployed off the beaches of South Africa from 1952-1972, 1961-1972, and 1978-2003, respectively (Dudley and Simpfendorfer, 2006; Ferretti et al., 2010)
ery-independent data that reveal drastic declines in this scalloped hammerhead shark population since the early 1950s. Specifically, declines of 99 percent, 86 percent, and 64 percent have been estimated for S. lewini from catch rates in shark nets deployed off the beaches of South Africa from 1952-1972, 1961-1972, and 1978-2003, respectively (Dudley and Simpfendorfer, 2006; Ferretti et al., 2010). Estimates of the decline in Australian hammerhead abundance range from 58-85 percent (Heupel and McAuley 2007; CITES, 2010). CPUE data from the northern Australian shark fishery indicate declines of 58-76 percent in hammerhead abundance in Australia's northwest marine region from 1996-2005 (Heupel and McAuley, 2007). Data from protective shark meshing programs off beaches in New South Wales (NSW) and Queensland also suggest significant declines in hammerhead populations off the east coast of Australia. From 1973 to 2008, the number of hammerheads caught per year in NSW beach nets decreased by more than 90 percent, from over 300 individuals to fewer than 30 (Reid and Krogh, 1992; Williamson, 2011). Similarly, data from the Queensland shark control program indicate declines of around 79 percent in hammerhead shark abundance between the years of 1986 and 2010, with S. lewini abundance fluctuating over the years but showing a recent decline of 63 percent between 2005 and 2010 (QLD DEEDI, 2011). Although these studies provide evidence of declining local populations, there is a high degree of uncertainty regarding the overall population size given the expansive range of this DPS.
Additionally, the ERA team noted that the coastal habitats of this DPS, especially around the island nations of the western Pacific, are less connected than those of the other DPSs that have a contiguous coastline. But since the western Pacific islands are relatively close together or connected by various submarine features, the ERA team felt that these areas are easily accessible to this DPS and therefore should pose minimal ecological risk
stal habitats of this DPS, especially around the island nations of the western Pacific, are less connected than those of the other DPSs that have a contiguous coastline. But since the western Pacific islands are relatively close together or connected by various submarine features, the ERA team felt that these areas are easily accessible to this DPS and therefore should pose minimal ecological risk. Overall, the ERA team recognized that the total abundance for this species in the entire region is not well known, but the available data confirm localized depletions of populations. This information, coupled with the species' low intrinsic rate of productivity, led the ERA team to conclude that the abundance in the foreseeable future may decline to a level that would not provide the DPS adequate resilience to environmental or anthropogenic perturbations. We agree with the ERA team's findings.
Central Pacific DPS
Abundance in this DPS is perceived to be high based on shark pup data from this region as well as personal observations from NMFS fishery scientists in the Pacific Islands Fishery Science Center. In Kāne‘ohe Bay, a large nursery ground in Oahu, Hawaii, estimates of 7700 ± 2240 SD scalloped hammerhead sharks are born per year, which suggests that between 180 and 660 adult female sharks use this area annually as a birthing ground (Duncan and Holland, 2006). Growth rate of these pups is estimated to be 9.6 cm per year (Duncan and Holland, 2006). Although Clarke (1971) observed high predation on the pups by adult scalloped hammerheads, the author noted that the pup population remained high and suggested that either the pup population is significantly larger than previously thought, or that new births are compensating for the mortality of the pups in this nursery ground.
With respect to spatial structure and connectivity, this DPS has a high degree of isolation
observed high predation on the pups by adult scalloped hammerheads, the author noted that the pup population remained high and suggested that either the pup population is significantly larger than previously thought, or that new births are compensating for the mortality of the pups in this nursery ground.
With respect to spatial structure and connectivity, this DPS has a high degree of isolation. However, while the population is limited in its connection to other coastal habitat areas, the fragmented habitats that are within this DPS are traversable, connected by various submarine features like seamounts and guyots. In addition, a number of suitable nursery grounds have been identified within this DPS. Thus, although the isolation of the DPS in the middle of the Pacific Ocean may pose a moderate risk to the species, the ERA team concluded, and we agree, that high abundance numbers and ample suitable nursery habitats protect the scalloped hammerhead shark population from extinction, with current levels of abundance unlikely to contribute significantly to this DPS' risk of extinction now or in the foreseeable future.
Eastern Pacific DPS
The ERA team commented that there are few good abundance data from this region; however, reports of substantial legal and illegal takes of S. lewini, and observed declines in scalloped hammerhead abundance and overall shark abundance, including in protected waters, suggest significant reductions in abundance of this species. Scalloped hammerhead sharks of all age classes are caught in substantial numbers by fisheries operating in this region (Perez-Jimenez et al., 2005; Román-Vedesoto and Orozco-Zöller 2005; INP, 2006; Bizarro et al., 2009; Arriatti, 2011). Some artisanal fisheries primarily target juvenile S. lewini (Arriatti, 2011), while other fisheries, like the tuna purse seine fisheries, catch significant numbers of the sharks as bycatch (Román-Vedesoto and Orozco-Zöller, 2005)
ntial numbers by fisheries operating in this region (Perez-Jimenez et al., 2005; Román-Vedesoto and Orozco-Zöller 2005; INP, 2006; Bizarro et al., 2009; Arriatti, 2011). Some artisanal fisheries primarily target juvenile S. lewini (Arriatti, 2011), while other fisheries, like the tuna purse seine fisheries, catch significant numbers of the sharks as bycatch (Román-Vedesoto and Orozco-Zöller, 2005). In the Gulf of Tehuantepac, in Pacific southeastern Mexico, it is estimated that the scalloped hammerhead population is currently decreasing by 6 percent per year (INP, 2006). From 1996-2001, CPUE of all sharks in the Gulf of Tehuantepac declined by around 46 percent, and for S. lewini, CPUE declined to nearly zero in 2001 (INP, 2006). Farther south, in the Costa Rica EEZ, analysis of survey research and catch data from 1991-1992 and 1999-2000 indicate a decline of 58 percent in relative pelagic shark abundance (Arauz et al., 2004). In Costa Rica's Pacific mahi-mahi targeted longline fishery, the mean CPUE (per 1,000 hooks) of S. lewini between 1999 and 2008 was low (0.041 ± 0.279); however, the majority of the fishing effort was concentrated in pelagic waters (from 19.5 to 596.2 km offshore) (Whoriskey et al., 2011). More troubling are the diver reports of S. lewini populations in the protected waters around Cocos Island National Park. Analysis of these reports indicate declines of 71 percent in this protected S. lewini population, and suggest substantial fishing on this population by illegal, unreported, and unregulated (IUU) fishing vessels (Myers et al., n.d.). Furthermore, landings data from the Pacific Mexican coast suggest a possible size truncation of this S. lewini population, with larger animals less common in 2007-2009 landings compared to those from 1998-1999 (Bizarro et al., 2009). The removal of larger, and hence, likely mature animals can decrease the productivity of the population, particularly for slow-growing, long-lived species such as the scalloped hammerhead shark
from the Pacific Mexican coast suggest a possible size truncation of this S. lewini population, with larger animals less common in 2007-2009 landings compared to those from 1998-1999 (Bizarro et al., 2009). The removal of larger, and hence, likely mature animals can decrease the productivity of the population, particularly for slow-growing, long-lived species such as the scalloped hammerhead shark. From an evolutionary standpoint, Nance et al. (2011) calculated that this DPS has undergone significant declines (1-3
Summary of Factors Affecting the Six DPSs of Scalloped Hammerhead Sharks
As described above, section 4(a)(1) of the ESA and NMFS implementing regulations (50 CFR 424) state that we must determine whether a species is endangered or threatened because of any one or a combination of the following factors: (1) The present or threatened destruction, modification, or curtailment of its habitat or range; (2) overutilization for commercial, recreational, scientific, or educational purposes; (3) disease or predation; (4) inadequacy of existing regulatory mechanisms; or (5) other natural or man-made factors affecting its continued existence. The ERA team evaluated whether and the extent to which each of the foregoing factors contributed to the overall extinction risk of the six DPSs. The status report identifies the most serious individual threat(s) to a DPS' persistence. It also identifies those threats that, in combination with others, were thought to contribute significantly to the risk of a DPS' extinction. This section briefly summarizes the ERA team's findings and our conclusions regarding threats to scalloped hammerhead sharks with occasional focus on threats specific to individual DPSs. More details can be found in the status review report (Miller et al., 2013)
lso identifies those threats that, in combination with others, were thought to contribute significantly to the risk of a DPS' extinction. This section briefly summarizes the ERA team's findings and our conclusions regarding threats to scalloped hammerhead sharks with occasional focus on threats specific to individual DPSs. More details can be found in the status review report (Miller et al., 2013).
The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range
The ERA team identified habitat destruction as a potential threat to the scalloped hammerhead shark, but did not find evidence to suggest that it is presently contributing significantly to any of the DPS's risks of extinction. Currently, scalloped hammerhead sharks are found worldwide, residing in coastal warm temperate and tropical seas and rarely in waters cooler than 22 °C (Compagno, 1984; Schulze-Haugen and Kohler, 2003). They occur over continental and insular shelves and adjacent deep waters, but can also be found in intertidal and surface waters and depths of up to 450 to 512 m (Sanches, 1991; Klimley, 1993). Estuaries and coastal embayments have been identified as particularly important nursery areas for scalloped hammerhead sharks range wide, while offshore waters contain important spawning and feeding areas. The vertical habitat of scalloped hammerheads in the Gulf of California may extend even farther to include areas of cold hypoxic waters (Jorgensen et al., 2009), indicating an ability to tolerate large fluctuations in temperature and dissolved oxygen concentrations.
In the U.S. EEZ, the MSA requires NMFS to identify and describe EFH in FMPs, minimize the adverse effects of fishing on EFH, and identify actions to encourage the conservation and enhancement of EFH. Towards that end, NMFS has funded two cooperative survey programs intended to help delineate shark nursery habitats in the Atlantic and Gulf of Mexico
emperature and dissolved oxygen concentrations.
In the U.S. EEZ, the MSA requires NMFS to identify and describe EFH in FMPs, minimize the adverse effects of fishing on EFH, and identify actions to encourage the conservation and enhancement of EFH. Towards that end, NMFS has funded two cooperative survey programs intended to help delineate shark nursery habitats in the Atlantic and Gulf of Mexico. The Cooperative Atlantic States Shark Pupping and Nursery Survey and the Cooperative Gulf of Mexico States Shark Pupping and Nursery Survey are designed to assess the geographical and seasonal extent of shark nursery habitat, determine which shark species use these areas, and gauge the relative importance of these coastal habitats for use in EFH determinations. Results from the surveys indicate the importance of estuarine, nearshore, and coastal waters of South Carolina, Georgia, Atlantic Florida, Florida Panhandle, and Alabama as potential nursery habitats for scalloped hammerhead sharks along the eastern U.S. Coast and Gulf of Mexico. Since the scalloped hammerhead EFH is defined as the water column or attributes of the water column, NMFS determined that there are minimal or no cumulative anticipated impacts to the EFH from gear used in HMS and non-HMS fisheries, basing its finding on an examination of published literature and anecdotal evidence (NMFS, 2006).
Likewise, scalloped hammerhead shark habitat in the other DPSs is similar to what is found in the NW Atlantic & GOM DPS, characterized primarily by the water column attributes. For example, Zeeberg et al. (2006) noted an increase in abundance of hammerhead bycatch in pelagic trawlers operating in the Mauritania EEZ during the summer months, which suggested frequent use of these waters as habitat areas by scalloped hammerheads
d shark habitat in the other DPSs is similar to what is found in the NW Atlantic & GOM DPS, characterized primarily by the water column attributes. For example, Zeeberg et al. (2006) noted an increase in abundance of hammerhead bycatch in pelagic trawlers operating in the Mauritania EEZ during the summer months, which suggested frequent use of these waters as habitat areas by scalloped hammerheads. However, bycatch probability decreased significantly during the winter and spring, as trade wind-induced upwellings caused sea surface temperatures to drop from summer maximums of 30 °C to 18 °C, indicating sea surface temperature as a significant habitat determinant. Likewise, Bessudo et al. (2011) found that the depth at which scalloped hammerhead sharks commonly swam around Malpelo Island in the Eastern Pacific coincided with the thermocline, the temperature-based transition layer between the mixed layer at the surface and the deep water layer. The authors also suggested that scalloped hammerhead seasonal movements to and from the island of Malpelo are linked to oceanographic conditions, with seasonal environmental signals triggering the migratory movements (Bessudo et al., 2011).
To date, no studies have looked at habitat alteration effects on scalloped hammerhead shark populations. However, any modifications would most likely affect S. lewini nursery habitats as these waters are usually shallower, located closer inshore, and thus are more susceptible to anthropogenic inputs than the offshore habitats. Examples of identified scalloped hammerhead pupping grounds include the Tárcoles River in the Gulf of Nicoya, Guam's Apra Harbor, Kāne‘ohe Bay in Oahu, Hawaii, and coastal waters off Oaxaca, Mexico and the Republic of Transkei. These waters are or may be used by humans for a variety of purposes that often result in degradation of these and adjacent habitats, posing threats, either directly or indirectly, to the biota they support (NMFS, 2006)
pping grounds include the Tárcoles River in the Gulf of Nicoya, Guam's Apra Harbor, Kāne‘ohe Bay in Oahu, Hawaii, and coastal waters off Oaxaca, Mexico and the Republic of Transkei. These waters are or may be used by humans for a variety of purposes that often result in degradation of these and adjacent habitats, posing threats, either directly or indirectly, to the biota they support (NMFS, 2006). These effects, either alone or in combination with effects from other activities within the ecosystem, may contribute to the decline of the species or degradation of the habitat. The ERA team specifically noted that the increased industrialization seen within the scalloped hammerhead shark range could result in loss of coastal and nearshore habitats and higher pollutants in waters used by the scalloped hammerhead shark. For example, in Costa Rica, the increased industrialization and subsequent waste from commercial, industrial, and transportation activities, as well as coffee production and cattle farming, has led to the accumulation of heavy metals near the mouth of a river frequently used as a scalloped hammerhead shark nursery ground (Zanella et al., 2009). High et al., 2002); however, such effects to S. lewini have not yet been reported in this area or elsewhere in the species' range. Although severe pollution and the degradation of water quality may be serious threats to S. lewini nursery and juvenile habitats range wide, the ERA team also noted that this species usually prefers more turbid and murkier waters. Data from Kāne‘ohe Bay in Hawaii show that juvenile scalloped hammerheads prefer to aggregate in deeper water during the day, where the habitat is composed mainly of mud and silt (Duncan and Holland, 2006). Areas of higher hammerhead shark abundance also corresponded to locations of greater turbidity and higher sedimentation and nutrient flow (Duncan and Holland, 2006)
e turbid and murkier waters. Data from Kāne‘ohe Bay in Hawaii show that juvenile scalloped hammerheads prefer to aggregate in deeper water during the day, where the habitat is composed mainly of mud and silt (Duncan and Holland, 2006). Areas of higher hammerhead shark abundance also corresponded to locations of greater turbidity and higher sedimentation and nutrient flow (Duncan and Holland, 2006). This was also true of scalloped hammerheads in the Eastern Pacific, with large adult schools gathering on the sides of islands where the current was strongest, and juvenile scalloped hammerheads frequenting shallow, turbid waters at the mouth of rivers (Garro et al., 2009; Zanella et al., 2009). As such, characteristics usually associated with coastal habitat degradation (such as runoff, siltation, eutrophication, etc.) could actually enhance some of the habitat for this species to a degree, creating more sediment and nutrient rich waters.
Because the scalloped hammerhead range is mainly comprised of open ocean environments occurring over broad geographic ranges, large-scale impacts such as global climate change that affect ocean temperatures, currents, and potentially food chain dynamics, are most likely to pose the greatest threat to this species. Additionally, the scalloped hammerhead shark is highly mobile within the range of its DPS, and there is no evidence to suggest its access to essential habitat is restricted within any of the DPSs. It also does not participate in natal homing, which would essentially restrict the species to a specific nursery ground, but rather has been found utilizing artificially enlarged estuaries as nursery habitats located 100 to 600 km from established nursery grounds (Duncan et al., 2006). Also, based on a comparison of S. lewini distribution maps from 1984 (Compagno, 1984) and 2012 (Bester, n.d.), and current reports of scalloped hammerhead catches in FAO fishing areas, there is no evidence to suggest a range contraction for any DPS based on habitat degradation
ially enlarged estuaries as nursery habitats located 100 to 600 km from established nursery grounds (Duncan et al., 2006). Also, based on a comparison of S. lewini distribution maps from 1984 (Compagno, 1984) and 2012 (Bester, n.d.), and current reports of scalloped hammerhead catches in FAO fishing areas, there is no evidence to suggest a range contraction for any DPS based on habitat degradation. Overall, using the best available information, there is no evidence to suggest there exists a present or threatened destruction, modification, or curtailment of the scalloped hammerhead shark's habitat or range and we conclude that it is unlikely that this factor is contributing on its own or in combination with other factors to the extinction risk of any of the six DPSs evaluated.
Overutilization for Commercial, Recreational, Scientific or Educational Purposes
The ERA team identified overutilization for commercial and/or recreational purposes as a moderate to major threat contributing to extinction risk for all six scalloped hammerhead shark DPSs. Scalloped hammerhead sharks are targeted by industrial, commercial, artisanal and recreational fisheries, and caught as bycatch in many other fisheries, including pelagic longline tuna and swordfish fisheries and purse seine fisheries. Unfortunately, significant catches of scalloped hammerheads have and continue to go unrecorded in many countries. In addition, scalloped hammerheads are likely under-reported in catch records, as many records do not account for discards (example: Where the fins are kept but the carcass is discarded) or reflect dressed weights instead of live weights. Also, many catch records do not differentiate between the hammerhead species, or shark species in general, and thus species-specific population trends for scalloped hammerheads are not readily available
kely under-reported in catch records, as many records do not account for discards (example: Where the fins are kept but the carcass is discarded) or reflect dressed weights instead of live weights. Also, many catch records do not differentiate between the hammerhead species, or shark species in general, and thus species-specific population trends for scalloped hammerheads are not readily available. Thus, the lack of catch data on scalloped hammerhead sharks makes it impossible to estimate rates of fishing mortality for many of the DPSs, or conduct detailed quantitative analyses of the effects of fishing on the scalloped hammerhead populations. Nonetheless, there is little doubt that overfishing has played a major role in the decline of scalloped hammerhead sharks, and many other shark species for that matter, around the world (Lack and Sant, 2011).
Estimates of worldwide catches of sphyrnids are reported in the FAO Global Capture Production dataset mainly at the family level, but a select number of countries have reported down to the species level. Total catches of the hammerhead family have increased since the early 1990s (prior years were not reported), from 377 mt in 1991 to a current peak of 5,786 mt in 2010. This rise is in contrast to the catches of S. lewini, which have decreased, for the most part, since reaching a maximum of 798 mt in 2002, suggesting a possible decline in population abundance. However, only seven countries have reported S. lewini data in this FAO database, which is by no means an accurate representation of worldwide S. lewini landings data. Additionally, these FAO data do not include discard mortalities. In order to gain a better estimate of the global shark catch, the ERA team reviewed a study by Clarke et al. (2006a, 2006b), which analyzed 1999-2001 Hong Kong fin trade auction data in conjunction with species-specific fin weights and genetic information
is by no means an accurate representation of worldwide S. lewini landings data. Additionally, these FAO data do not include discard mortalities. In order to gain a better estimate of the global shark catch, the ERA team reviewed a study by Clarke et al. (2006a, 2006b), which analyzed 1999-2001 Hong Kong fin trade auction data in conjunction with species-specific fin weights and genetic information. Scalloped hammerhead sharks are popular in the international fin trade due to their large fins with a high fin needle content (a gelatinous product used to make shark fin soup), and subsequently fetch a high commercial price (Abercrombie et al., 2005). These fins are found under the second most traded fin category in the Hong Kong market. Applying a Bayesian statistical method to the trade auction data, it was estimated that between 1 and 3 million smooth and scalloped hammerhead sharks, with an equivalent biomass of 60-70 thousand mt, are traded annually (Clarke et al., 2006b). These estimates are significantly higher than the catches reported to FAO, and suggest that FAO catch data should only be used as coarse estimates. To put these numbers into perspective, Hayes et al. (2009) estimated the virgin, or unfished, population size (in 1981) of the Northwest Atlantic and Gulf of Mexico scalloped hammerhead stock to be in the range of 142,000—169,000 individuals.
Given the high exploitation rates and vulnerability of the scalloped hammerhead shark to overfishing, the ERA team identified overutilization, especially for the international fin trade, as the most severe threat to the global scalloped hammerhead shark population. With respect to each DPS, the severity of this threat to its risk of extinction is briefly explained below.
NW Atlantic & GOM DPS
The ERA team identified the threat of overutilization by commercial and recreational fisheries as a moderate risk to the extinction of the NW Atlantic & GOM DPS of scalloped hammerhead sharks, but projected the threat to decrease in the foreseeable future
opulation. With respect to each DPS, the severity of this threat to its risk of extinction is briefly explained below.
NW Atlantic & GOM DPS
The ERA team identified the threat of overutilization by commercial and recreational fisheries as a moderate risk to the extinction of the NW Atlantic & GOM DPS of scalloped hammerhead sharks, but projected the threat to decrease in the foreseeable future. In the Atlantic U.S., scalloped hammerhead sharks are considered a highly migratory species (HMS), with this DPS managed as part of the U.S. Atlantic HMS fisheries. These scalloped hammerhead sharks are mainly caught by directed shark permit holders using bottom longline gear. To a lesser degree they are caught as bycatch in longline and coastal gillnet fisheries. In the recreational fisheries sector, scalloped et al., 2009). Data from multiple sources indicate that the NW Atlantic & GOM DPS has experienced severe declines over the past few decades. It is likely that these scalloped hammerhead sharks were overfished beginning in the early 1980s and experienced periodic overfishing from 1983 to 2005 (Jiao et al., 2011).
In October 2009, Hayes et al. (2009) produced a stock assessment for the U.S. Northwest Atlantic and Gulf of Mexico population of scalloped hammerhead sharks, which NMFS reviewed and deemed appropriate for the basis of U.S. management decisions. The stock assessment incorporated both recreational and commercial catch information as well as discard estimates since 1981, and developed abundance indices from fishery-dependent and -independent surveys. From 1981-1990, a total of 181,544 scalloped hammerhead sharks from the NW Atlantic & GOM DPS were estimated as caught, primarily by recreational fishers. In fact, the recreational fishery sector accounted for over 90 percent of this harvest
nal and commercial catch information as well as discard estimates since 1981, and developed abundance indices from fishery-dependent and -independent surveys. From 1981-1990, a total of 181,544 scalloped hammerhead sharks from the NW Atlantic & GOM DPS were estimated as caught, primari

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Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/FR_PRORULE_2013-07781. Check the current official text before relying on it. Not legal advice.