Endangered and Threatened Wildlife and Plants; Final Rule To List the Rio Grande Silvery Minnow as an Endangered Species

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AB88

Endangered and Threatened Wildlife and Plants; Final Rule To List

the Rio Grande Silvery Minnow as an Endangered Species

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: The U.S. Fish and Wildlife Service (Service) determines the

Rio Grande silvery minnow (Hybognathus amarus) to be an endangered

species under the Endangered Species Act of 1973 (Act), as amended.

This fish occurs only in the middle Rio Grande from Cochiti Dam

downstream to the headwaters of Elephant Butte Reservoir, New Mexico.

Threats to the species include dewatering, channelization and

regulation of river flow to provide water for irrigation; diminished

water quality caused by municipal, industrial, and agricultural

discharges; and competition or predation by introduced non-native fish

species. Currently, the species occupies about five percent of its

known historic range. This action will implement Federal protection

provided by the Act for the Rio Grande silvery minnow. The Service

further determines that finalization of proposed critical habitat will

not occur at this time, as critical habitat is not now determinable

because the required economic analysis has not been completed. Pursuant

to section 4(b)(6)(C)(ii) of the Act, a final determination on critical

habitat may be delayed up to 1 year beyond the normal deadline.

EFFECTIVE DATE: August 19, 1994.

ADDRESSES: The complete file for this rule is available for inspection,

by appointment, during normal business hours at the U.S. Fish and

Wildlife Service, New Mexico Ecological Services State Office, 3530 Pan

American Highway NE., Suite D, Albuquerque, New Mexico 87107.

FOR FURTHER INFORMATION CONTACT: Jennifer Fowler-Propst, State

Supervisor, at the above address (505/883-7877).

SUPPLEMENTARY INFORMATION:

Background

The Rio Grande silvery minnow is one of seven species in the genus

Hybognathus found in the United States (Pflieger 1980). The species was

first described by Girard (1856) from specimens taken from the Rio

Grande near Fort Brown, Cameron County, Texas. It is a stout silvery

minnow with moderately small eyes and a small, slightly oblique mouth

(Pflieger 1975). Adults may reach 90 mm (3.5 in) in total length

(Sublette et al. 1990). Its dorsal fin is distinctly pointed with the

front located slightly closer to the tip of the snout than to the base

of the tail (Pflieger 1975). Life color is silver with emerald

reflections. Its belly is silvery white, fins are plain, and barbels

are absent (Pflieger 1975, Sublette et al. 1990).

This species was historically one of the most abundant and

widespread fishes in the Rio Grande basin, occurring from Espanola, New

Mexico, to the Gulf of Mexico (Bestgen and Platania 1991). It was also

found in the Pecos River, a major tributary of the Rio Grande, from

Santa Rosa, New Mexico, downstream to its confluence with the Rio

Grande in south Texas (Pflieger 1980). Collection data indicate the

species presently occupies about five percent of its historic range

(Platania 1993). It has been completely extirpated from the Pecos River

and from the Rio Grande downstream of Elephant Butte Reservoir.

Currently, it is found only in a 275 km (170 mi) reach of the middle

Rio Grande, New Mexico, from Cochiti Dam, Sandoval County, to the

headwaters of Elephant Butte Reservoir, Socorro County (Bestgen and

Platania 1991). Throughout much of its historic range, decline of H.

amarus may be attributed to modification of stream discharge patterns

and channel desiccation by impoundments, water diversion for

agriculture, and stream channelization (Bestgen and Platania 1991, Cook

et al. 1992).

The Rio Grande silvery minnow no longer exists in the Pecos River

where it was replaced by a congener, the introduced plains minnow (H.

placitus) (Hatch et al. 1985, Bestgen et al. 1989, Cook et al. 1992).

It is believed that the plains minnow was introduced into the Pecos

drainage during 1968, probably the result of the release of ``bait

minnows'' that were collected from the Arkansas River drainage. The

replacement that ensued was complete in less than one decade (Cowley

1979). The plains minnow may be more tolerant of modified habitats and

therefore able to replace H. amarus in the modified reaches of the

Pecos River where it was introduced. It is also believed the two

species hybridized (Cook et al. 1992). Habitat alteration and resulting

flow modification could have also contributed to extirpation of the Rio

Grande silvery minnow in the Pecos River.

Decline of the species in the Rio Grande probably began in 1916

when the gates at Elephant Butte Dam were closed. Elephant Butte was

the first of five major mainstream dams constructed within the Rio

Grande silvery minnow's habitat (Shupe and Williams 1988). These dams

allowed the flow of the river to be manipulated and diverted for the

benefit of agriculture. Often this manipulation resulted in the

desiccation of some river reaches and elimination of all fish.

Concurrent with construction of the mainstream dams was an increase in

the abundance of non-native and exotic fish species, as these species

were stocked into the reservoirs created by the dams (Sublette et al.

1990). Once established, these species often completely replaced the

native fish fauna (Propst et al. 1987). Development of agriculture and

the growth of cities within the historic range of H. amarus resulted in

a decrease in the quality of water in the river that may have adversely

affected the range and distribution of the species.

Most land bordering the river where the species currently exists is

owned by the Middle Rio Grande Conservancy District, which is a quasi-

public agency of the State of New Mexico. Other landowners include six

Native American Pueblos, the U.S. Bureau of Reclamation, the Service,

the U.S. Bureau of Land Management, New Mexico State Parks, New Mexico

Department of Game and Fish, New Mexico State Lands Department, and the

U.S. Army Corps of Engineers (Corps).

Water flow in the middle Rio Grande is controlled by the Rio Grande

Compact Commission. Established in 1929 for the purpose of permanently

and equitably apportioning the flows of the Rio Grande, the Commission

is composed of a Federal chairperson appointed by the President of the

United States and three voting members--a representative designated by

the Texas Governor and the State Engineers of New Mexico and Colorado.

The Commission meets annually to review compliance with the compact

over the preceding year, to hear reports from Federal water management

agencies, and to consider water management decisions that have

interstate implications. Federal agencies that also determine timing

and amount of flow in the river include the International Boundary and

Water Commission, the Bureau of Reclamation, and the Corps.

Previous Service Actions

The Rio Grande silvery minnow was listed on the Service's Animal

Notice of Review (56 FR 58804; November 21, 1991) as a category 1

species. A category 1 species is one for which the Service has on file

substantial information on biological vulnerability and threat(s) to

support a proposal to list it as an endangered or threatened species. A

proposed rule to list the Rio Grande silvery minnow as endangered with

critical habitat was published in the Federal Register on March 1, 1993

(58 FR 11821).

Summary of Comments and Recommendations

In the March 1, 1993, proposed rule and associated notifications,

all interested parties were requested to submit factual reports or

information that might contribute to the development of a final rule.

The comment period originally scheduled to close on April 30, 1993, was

extended until August 25, 1993, (58 FR 19220; April 13, 1993) to

conduct public hearings and allow submission of additional comments.

Appropriate Tribal governments, State agencies, county governments,

Federal agencies, scientific organizations, and other interested

parties were contacted and requested to comment. Newspaper notices

inviting public comment were published in New Mexico in the Albuquerque

Journal on May 2, 1993; Las Cruces Sun News on April 30, 1993; Socorro

Defensor Chieftain on April 28, 1993; Santa Fe New Mexican on April 20,

1993; and in Texas in the El Paso Times on March 20, 1993.

Because of anticipated widespread public interest, the Service held

two public hearings that were announced in an April 13, 1993, Federal

Register notice. Interested parties were contacted and notified of the

hearings. Thirty-seven people attended the hearing in Albuquerque, New

Mexico, and 58 attended the hearing in Socorro, New Mexico. Oral or

written comments were received from 25 parties at the hearings; none

directly supported the proposed listing. Transcripts of these hearings

are available for inspection (see ADDRESSES). Briefing sessions were

also held for tribal leaders on May 18, 1993, in Albuquerque, New

Mexico; and for a number of northern pueblos at Santo Domingo Pueblo,

New Mexico, on September 9, 1993.

A total of 40 written comments were received at the Service's

Ecological Services State Office in Albuquerque, New Mexico: 13

supported the proposed listing; 14 opposed the proposed listing; and 13

commented on information in the proposed rule but expressed neither

support nor opposition.

Oral or written comments were received from 7 Federal and 5 state

agencies, 14 local officials, and 36 private organizations, companies,

and individuals. Written comments and oral statements presented at the

public hearings and received during the comment periods are covered in

the following summary. Comments of a similar nature or point are

grouped into a number of general issues. These issues, and the

Service's response to each, are discussed below.

Issue 1: The Service has come to the conclusion that only instream

flow will assure the species' existence. Will the Service propose a

program for the purchase of water rights in order to provide water for

the species?

Response: The Service has not reached this conclusion. Possible

instream flow requirements of the species are among several factors

that need to be considered in the recovery planning process. If, during

the recovery planning process, the Service determines that the purchase

of water rights will enhance recovery of the species, the Service would

explore with other State and Federal entities the possible purchase of

water rights from willing sellers.

Issue 2: The United States, under the terms of the Convention of

1906, has the obligation to deliver 60,000 acre-feet of water annually

to the Republic of Mexico. The U.S. International Boundary and Water

Commission (IBWC) is responsible for ensuring that the U.S. government

meets those obligations. The IBWC is concerned that the listing may

interfere with their ability to meet these treaty requirements.

Response: The Service recognizes the treaty obligation of the

United States to provide to the Republic of Mexico 60,000 acre-feet of

water annually from the Rio Grande. Measures taken to protect and

recover the Rio Grande silvery minnow will take into consideration this

treaty obligation and IBWC's ability to meet treaty requirements.

Issue 3: Completion of the dams above Elephant Butte Dam has had

the effect of extending stream flow. Flood control and conservation

storage operations do not, cannot, and have not been used to create or

extend reaches of no flow in the riverbed.

Response: The Service agrees with the statement. Availability of

flow is likely not the only factor affecting decline of the silvery

minnow. These operations change the natural flow regime of the river

and thus may affect survival of the Rio Grande silvery minnow. The

final rule recognizes these other factors in the ``Summary of Factors

Affecting the Species.''

Issue 4: Reservoirs do not, as implied, store all spring runoff and

summer inflows. Water is normally released during summer, not winter

months. Diversion dams and canals have limited capacities to divert

flows. They cannot ``completely divert all flows . . . into irrigation

ditches'' under flood conditions.

Response: The Service agrees with the statement that reservoirs do

not store all spring runoff and summer inflow. While most water is

released during the spring and summer, a fall and winter release does

occur in the Middle Rio Grande Valley when conditions permit (Beal and

Gold 1988, Borland and Gold 1989). Under flood conditions, the

irrigation diversions do not have the capacity to divert all flows.

Under non-flood flows they do have the capacity to divert all flows.

United States Geological Survey (USGS) records substantiate the

occurrence of no-flow periods downstream of the various irrigation

diversion dams.

Issue 5: The proposed regulation is unsupported by any hydrological

study as to the statements that irrigation uses have depleted the water

flow. Not a single source of information is cited for comments

regarding hydrology of the river. Depletions of water in the system may

be the result of the construction of wildlife watering impoundments by

the Forest Service and Bureau of Land Management.

Response: It can be readily documented by examining USGS flow gage

records that river flows decrease when the irrigation season starts. In

addition, the Service reviewed Bullard and Wells (1992), which provides

information on the hydrology of the middle Rio Grande. This reduction

in flow is most noticeable in mid-summer after the spring to early

summer peak flow has passed. Wildlife impoundments are often very small

(less than one acre in size) and are considered to be insignificant in

the amount of water they deplete from the drainage.

Issue 6: Economic considerations should be given more weight when

communities may be affected.

Response: Section 4(a)(1) of the Act identifies five factors that

are considered in making a determination of whether a species should be

listed as threatened or endangered. Section 4(b)(1)(A) of the Act

requires that listing determinations be based solely on the best

available scientific and commercial data, and prohibits the Service

from considering economic factors (50 CFR 424.11(b)). However, because

economics are considered in the designation of critical habitat, the

Service will conduct an economic analysis in the process of evaluating

proposed critical habitat for the Rio Grande silvery minnow.

Issue 7: The Service needs to ensure public input before listing

the Rio Grande silvery minnow. The Service is required to notify

counties and other affected parties to solicit their input prior to

listing a species under the Act. The Service failed to meet this

obligation.

Response: On February 19, 1991, about 80 pre-proposal letters of

inquiry were mailed to various governmental agencies, knowledgeable

individuals, and the New Mexico Congressional delegation. On March 20,

1992, the Service held a meeting in Albuquerque, New Mexico, with

various interested governmental and private entities to explore

existing or potential flexibility in water delivery schedules that

might avoid dewatering of the Rio Grande within the range of the Rio

Grande silvery minnow. The Service also published notices of the

proposal in 5 local newspapers and mailed copies of the proposed rule

to 148 different government agencies, private organizations, and

interested individuals, including all counties having lands that border

the area being proposed for critical habitat designation. Two public

hearings were also held. The Service has fully met or surpassed the

requirements of the Endangered Species Act for public notification.

Issue 8: The Service held public hearings only to fulfill a legal

obligation and will not pay attention to any public comment. The

Service should have held public hearings in El Paso and Las Cruces.

Response: The Service disagrees. All comments are carefully

evaluated before the Service makes a determination on whether to

proceed with a final rule. Numerous notifications of the proposed rule

and extension of the comment period were distributed, and Service

biologists traveled to several areas, including El Paso and Las Cruces,

to present briefings on the proposed rule and accept comments.

Issue 9: The Service should establish a coordinating committee

composed of interests below Elephant Butte Reservoir whose task would

be to develop a full-scale report on the existing data available on the

Rio Grande silvery minnow and how the river could be managed for the

benefit of all, including the Rio Grande silvery minnow.

Response: After the species is listed the Service will consider,

through the recovery planning process, establishing a coordinating

committee to develop a report on the Rio Grande silvery minnow and how

the river could be managed for the benefit of all, including the Rio

Grande silvery minnow.

Issue 10: During periods of dewatering of the river, the ditches

provide habitat for the species. The Service should consider exploring

with the Middle Rio Grande Conservancy District, the counties, and

other agencies the multiple use of riverside drains for the species and

the preservation of bosque habitat.

Response: The Service agrees that during periods of drought, which

result in the dewatering of the mainstream Rio Grande, the various

irrigation ditches and drains may provide a temporary place of refuge

for the Rio Grande silvery minnow. However, these areas do not contain

suitable habitat for long-term use by the species. Few Rio Grande

silvery minnows are found in the ditches and drains. Those that are

found are believed to represent Rio Grande silvery minnows that became

entrapped due to the diversion of irrigation water from the mainstream.

The Service intends to investigate, with all interests, the potential

use of the riverside drains for recovery of the species.

Issue 11: Few data exist on the abundance of the species on Pueblo

lands or whether it can survive in the mud and sand when the river bed

is dry.

Response: The Service used all available biological information in

making the determination to list the Rio Grande silvery minnow as an

endangered species. Recent census data from Pueblo lands are reported

by Bestgen and Platania (1991), Platania and Bestgen (1988), Platania

and Clemmer (1984), and the U.S. Bureau of Reclamation (1992). As

additional information becomes available, including information from

Pueblo waters, the Service will use that information in the recovery

planning process. The Service hopes that, through initiation of

recovery efforts for the species, and in cooperation with the Pueblos,

additional information can be obtained on the status of the species on

Pueblo lands. The Service has no scientific data indicating that the

species survives in the mud and sand during periods when the river is

dry.

Issue 12: Competition between H. amarus and its congener H.

placitus could have also contributed to extirpation of the species from

the Pecos River. Studies should be conducted to determine if predation

or competition by non-native fishes impacts the species. The studies

should not just determine if it is a problem, they should also

determine where and to what extent it is a problem.

Response: The Service has no data to substantiate any reasons for

extirpation of the Rio Grande silvery minnow from the Pecos River and

replacement by its congener H. placitus. Competition may have been a

factor in its extirpation; however, it is more likely that

hybridization between the two species was the primary factor. Studies

designed to determine if predation or competition by non-native fishes

impacts the survival of the Rio Grande silvery minnow will be conducted

as part of recovery efforts for the species.

Issue 13: Recent biological studies have been conducted during a

period of high flow; therefore, the results of those studies do not

accurately reflect the distribution of the species under normal

conditions.

Response: It is true that, other than 1989, recent data have been

collected during a period of higher than normal flow. However, even

these data show that the species is not as abundant as it was during

other periods of above-normal flow. This leads to a conclusion that

factors other than flow may be impacting the species and its habitat.

Issue 14: It seems a fair conclusion that the Cochiti downstream

reach is no longer favorable habitat because of lowered water

temperatures and degradation of favored H. amarus substrate. This

further limits the area in which the species has to survive.

Response: Although the reach immediately downstream of Cochiti Dam

may not be favorable habitat for the Rio Grande silvery minnow, it is

not known how far downstream these conditions persist. As part of

recovery efforts for the species, studies will be conducted on this

question, and attempts may be made to correct the unfavorable

conditions.

Issue 15: Since little is known of feeding habits or reproduction,

the claim that channel modification would adversely affect the Rio

Grande silvery minnow is not supported by the best scientific evidence.

Changes in food supply, not water supply, may be a factor affecting the

species in the Rio Grande. Also, the effects of non-native plants upon

the habitat need to be investigated.

Response: Recent data have shown that spawning activity occurs

during peak spring and early-summer flows. The fertilized eggs drift

with the current for about 24 hours and then hatch. The larval fish

continue to drift downstream until they are swept into calm backwater

and edge areas where food is abundant and they can continue to grow.

Because of this spawning behavior, any modifications to the channel

that result in changes that sweep the eggs and larval fish into less

favorable habitats would adversely affect the species. There are no

data presently available to support the contention that a reason for

decline of the species was a decrease in the species' food supply or

the invasion of non-native plants. As part of recovery efforts, the

impacts of all habitat modifications will be investigated to determine

if and how they impact the species.

Issue 16: Very little information was presented at the public

hearing or in the Federal Register to show a cause-and-effect

relationship between water quality and decline of the species.

Response: Limited information exists on the relationship between

water quality and the decline of the species. A better understanding of

this relationship will be developed as a result of recovery efforts.

Issue 17: The proposed listing of the Rio Grande silvery minnow is

just a part of a much larger problem--the modification of the

floodplain. Are activities at Bosque del Apache National Wildlife

Refuge (NWR) affecting the species?

Response: The Service agrees. Listing the species will invoke

protective provisions of the Act, such as those contained in section 7.

The Service has no information that indicates activities at Bosque del

Apache NWR impact the species. The Service will work with Federal

agencies, including Bosque del Apache NWR, to ensure that their actions

do not jeopardize the species through adverse effects on the

floodplain. In addition, the Service is involved in several cooperative

efforts with Federal, State, and private entities to protect the Rio

Grande Bosque and associated floodplain.

Issue 18: The facts presented in the status report do not support

the conclusion that ``anticipated additional modifications'' would

limit prospects of survival for the species in the middle Rio Grande.

Response: The facts presented in the status report do support the

conclusion that ``anticipated additional modifications'' would limit

prospects of survival for the species in the middle Rio Grande.

According to the authors of the status report, ``Conservation measures

are necessary as continued habitat and flow modifications,

introductions of non-native species, and lack of refugia threaten

survival of H. amarus.'' The present status of the species is such that

any activity that could negatively impact the species may limit

prospects for its survival.

Issue 19: Only two facts support listing; that the species is

presently found in only 5 percent of its historic range, and that other

fish native to the middle Rio Grande (Rio Grande bluntnose shiner,

phantom shiner, Rio Grande shiner, and speckled chub) have been

extirpated from the river. The Service does not have adequate data to

support the conclusion that the Rio Grande silvery minnow is endangered

and should be listed under the Act.

Response: The Service agrees that the above two facts support

listing. However, other facts that support listing include the species'

decrease in abundance within the area it presently occupies, and its

extirpation from the Pecos River after the introduction of the plains

minnow into that system. The Service concludes, as detailed in the

``Summary of Factors'' section, that there is sufficient evidence to

support listing the species as endangered under the Act. The Service

reviewed the best scientific and commercial data available to make this

determination.

Issue 20: The Rio Grande silvery minnow is not a distinct species.

It is just a local population of the Mississippi silvery minnow. The

Service should consider conducting studies for two years on the

species' taxonomy.

Response: The Service has taxonomic information that verifies the

Rio Grande silvery minnow as a distinct species. The Rio Grande silvery

minnow is recognized by the American Fisheries Society, which is

considered the scientific authority for the names of fishes, as a full

species (American Fisheries Society 1991). Cook et al. (1992), using

starch gel electrophoretic methods, found that phenetic and

phylogenetic analyses corroborated the hypothesis that H. amarus is

distinct at the species level from H. nuchalis and H. placitus, with

which it was previously grouped.

Issue 21: The Service has not conducted in-depth studies to

determine the number of silvery minnows that exist in the Middle Rio

Grande Valley and associated drainage ditches. The species may be doing

well without protection of the Federal government.

Response: Since 1987, studies have been conducted to document the

population of Rio Grande silvery minnows in both the Middle Rio Grande

Valley and its associated irrigation and drainage ditches from Velarde

to Elephant Butte Reservoir, New Mexico. These studies have shown that

very few Rio Grande silvery minnows survive in the drainage ditches.

The listing is based, in part, upon the extirpation of the species from

about 95 percent of its historic range. The species was once thought to

be one of the most numerous fish in the Rio Grande. In 50 fish

collections made between Bernalillo and Elephant Butte Reservoir

between 1987 and 1988, the Rio Grande silvery minnow was the second

most abundant species, comprising 18 percent of the total fish

collected. From 1989 to 1992, 56 collections were made in the same area

and only 3 Rio Grande silvery minnows were collected. During that

period, the Rio Grande silvery minnow went from being the second most

abundant native fish species to the least abundant native species

(Platania 1993). The Service believes that without the protection

afforded through Federal listing, the species is likely to become

extinct. Two native Rio Grande fish species have already become

extinct.

Issue 22: The fish exist in stretches of the river that have been

subject to drying for at least 50 years, but have disappeared from

areas where there has been instream flow for the past 50 years.

Response: The Service agrees that the species has persisted in

reaches of the river that have experienced seasonal drying during the

past 50 years and has been extirpated from reaches where there has been

continual flow during the last 50 years. In the past, during periods of

extremely low flow, the species survived in areas where irrigation

water returned to the river, in seepage and leakage pools located

downstream of irrigation diversion dams, and, prior to construction of

Cochiti Dam, in the canyon reach of the Rio Grande upstream of Cochiti.

Prior to the construction of irrigation and flood control dams in the

southwest, it was not unusual for portions of major rivers to become

dry during periods of drought. During these drought periods, native

fishes would retreat to canyon reaches where permanent water existed.

After the drought ended, they would re-inhabit the reaches of river

that had formerly been dry. There was a constant expansion and

contraction of fish populations. Construction of mainstream dams

prevented this movement and may have contributed to the extitirpation

of downstream populations of native fishes.

The reasons for the extirpation of the species from continual flow

reaches of the river are not known but probably relate to factors other

than flow. Changes in species composition, flow regimes, and water

quality could all have been causative factors in the decline of the Rio

Grande silvery minnow from these areas. Even in those areas where the

species presently persists, its abundance has been substantially

reduced (Platania 1993).

Issue 23: Listing is not necessary because of existing protection

that is afforded the species by the requirements of the Coordination

Act, National Environmental Policy Act, and other habitat protection

regulations, such as section 404 of the Clean Water Act. Any activity

that could affect the habitat of the species would have to undergo

these reviews, including the Middle Rio Grande Conservancy District's

work on its structures. Such work could not be done with impunity.

Protection is also provided to the species because of its listing as

endangered by the State of New Mexico.

Response: To date, the species has declined even with these

regulations in place. These regulations do not ensure that habitat for

the Rio Grande silvery minnow will be protected. Listing of the species

by the State of New Mexico only regulates collecting of the species. It

does not provide protection for its habitat or for its recovery. The

Service believes the protective mechanisms of the Act are necessary to

prevent the species' extinction.

Summary of Factors Affecting the Species

After a thorough review and consideration of all information

available, the Service has determined that the Rio Grande silvery

minnow should be classified as an endangered species. Procedures found

at section 4(a)(1) of the Act (16 U.S.C. 1531 et seq.), and regulations

(50 CFR Part 424) promulgated to implement the listing provisions of

the Act were followed. A species may be determined to be an endangered

or threatened species due to one or more of the five factors described

in section 4(a)(1). These factors and their application to the Rio

Grande silvery minnow (Hybognathus amarus) are as follows:

A. The Present or Threatened Destruction, Modification, or Curtailment

of Its Habitat or Range

The only existing population of H. amarus continues to be

threatened by annual dewatering of a large percentage of its habitat.

This dewatering is primarily the result of diversion of river flow for

agriculture within the Middle Rio Grande Valley of New Mexico. During a

year when an average or above-average amount of water is available, the

impacts of the diversions are not severe. During a below-average water

year, the river channel may be dry from Isleta Diversion Dam downstream

about 179 km (111 mi) to the headwaters of Elephant Butte Reservoir for

two months or more. When two below-average flow years occur

consecutively, a short-lived species such as H. amarus can be severely

affected, if not completely eliminated from the dry reaches of river.

During the 94 years for which flow records have been maintained for the

middle Rio Grande, it has not been unusual for the 245 km (153 mi)

reach of the Rio Grande from the Angostura Diversion Dam downstream to

Elephant Butte Reservoir to experience periods of no flow. Even before

construction of mainstream dams, the middle Rio Grande frequently

experienced periods of no flow. During such periods, it is suspected H.

amarus survived in areas where irrigation return flows re-entered the

river, in the pools formed by water leaking through the gates of the

diversion dams, in the irrigation ditches and drains, and in the

reaches of stream above the diversions from which their offspring could

repopulate downstream reaches when conditions permitted. It is not

known why these same factors do not provide sufficient habitat to

support H. amarus under current conditions. Other factors, such as an

increase in non-native and exotic fish species, or an increase in

contamination may be exacerbating the stress placed upon the species

during low-flow periods.

Mainstream dams permit the artificial regulation of flow, prevent

flooding, trap nutrients, alter sediment transport, prolong flows, and

create reservoirs that favor non-native fish species. These changes may

affect the Rio Grande silvery minnow by reducing its food supply,

altering its preferred habitat, preventing dispersal, and providing a

continual supply of non-native fishes that may compete with or prey

upon the species. Altering flow regimes may also improve conditions for

other native fish species that occupy the same habitat as the Rio

Grande silvery minnow and may thereby cause their populations to expand

at the expense of the Rio Grande silvery minnow.

Since completion of Elephant Butte Dam in 1916, four additional

mainstream dams have been constructed on the middle Rio Grande, and two

dams have been constructed on one of its major tributaries, the Rio

Chama (Shupe and Williams 1988). Construction and operation of these

dams, which are either irrigation diversion dams such as Angostura,

Isleta, and San Acacia; or flood control and water storage dams such as

Elephant Butte, Cochiti, Abiquiu, and El Vado, have modified the

natural flow of the river. The dams make it possible during a low-flow

year to completely divert all of the flow from the river channel into

irrigation ditches. The species does not persist in the irrigation

ditches or the low-flow conveyance channel. Platania (1993) collected

fish samples from 11 locations along the low-flow conveyance channel

between 1987-1989 and failed to locate any Rio Grande silvery minnows.

The dams also store spring runoff and summer inflow, which would

normally cause flooding, and release this water back into the river

channel over a prolonged period of time. This release is often made

during the winter months when low flows would normally occur.

Artificially-controlled flows depart significantly from natural

conditions. Reduced flows may limit the amount of preferred habitat

available to the species and may limit dispersal of the species.

Although the mechanisms of how the decline of the species occurred are

not fully understood, manipulation of flow may be one of the primary

reasons H. amarus has been extirpated from portions of its historic

range.

Channelization of the middle Rio Grande has resulted primarily from

the placement of Kellner jetty fields, or jacks, along the river. They

are designed to protect the levees by retarding flood flows, trapping

sediment, and promoting the establishment of vegetation. Since 1951,

the Bureau of Reclamation and Corps have installed in excess of 100,000

individual jetties occupying more than 2,000 ha (5,000 ac) (Bullard and

Wells 1992).

From Elephant Butte Dam downstream about 325 km (200 mi) to its

confluence with the Rio Conchos, the Rio Grande is fully controlled by

reservoir releases and irrigation return flows. Meanders, oxbows and

other components of historic aquatic habitat have been eliminated in

order to pass water as efficiently as possible for agricultural

irrigation and downstream deliveries. These changes affected the Rio

Grande silvery minnow by altering its habitat to the extent that its

survival was not possible. The sandy substrate, which it prefers, has

been replaced by gravel and cobble, and no backwater areas exist where

the young can develop. Winter flows released from Caballo Dam often

equal .06 cubic meters per second (2 cubic feet per second), which is

not enough flow to maintain habitat for fishes.

In 1958, in an effort to meet Rio Grande Compact water delivery

requirements, the Bureau of Reclamation initiated operation of a 97 km

(60 mi) long conveyance channel from San Acacia to Elephant Butte

Reservoir. The purpose of the conveyance channel is to divert all flow

less than 63 cubic meters per second (2000 cubic feet per second) in

order to prevent loss of the Rio Grande flow to seepage and evaporation

from the aggraded riverbed. Prior to 1985, the conveyance channel had

been operated to its full capacity for about 28 years. Since 1985, it

has not been operated at full capacity. If, however, the channel were

to be operated at full capacity, the natural stream bed downstream of

San Acacia would be dry more frequently and for longer periods of time.

Both the Corps and the Bureau of Reclamation are drafting plans to

rehabilitate and protect the conveyance channel in order to bring it

into full operation. Should the conveyance channel be placed in full

operation, the portion of the Rio Grande silvery minnow's habitat

downstream of San Acacia dam would be desiccated when river flows at

the dam became less than 63 cubic meters per second (2000 cubic feet

per second), resulting in death or displacement of individuals.

Water diversions also occur above the Middle Rio Grande Valley in

both Colorado and New Mexico. These diversions, which provide

irrigation for about 248,000 ha (620,000 ac) in Colorado and about

24,400 ha (61,000 ac) in New Mexico, have a significant effect on flows

(Cruz et al. 1993). In addition to these upstream diversions, about

94,000 acre-feet of water are diverted annually from the San Juan River

basin and transported via a tunnel into the Rio Grande basin. This

diversion may benefit the species since it is used to supplement flows

during periods of low flow.

Growth of agriculture and cities along the Rio Grande during the

last century may have adversely affected the quality of the river's

water. During low-flow periods, a large percentage of the river's flow

consists of municipal and agricultural discharge and less water is

available to dilute pollutants. This degradation of water quality may

affect H. amarus survival. Poor water quality in the Rio Grande near

Albuquerque, especially during low flows, may be a problem, as low

numbers of H. amarus and an overall reduced fish community are found

there (Bestgen and Platania 1991).

B. Overutilization for Commercial, Recreational, Scientific, or

Educational Purposes

It is not presently known if the species is being overutilized for

commercial, recreational, scientific, or educational purposes. New

Mexico Department of Game and Fish controls scientific taking of the

species through a permit process. Licensed commercial bait dealers may

sell bait minnows only within the drainage where they have been

collected. They are also restricted from selling any State-listed fish

species. However, it has been demonstrated on the Pecos River, New

Mexico, that often the dealers and retailers cannot identify listed

fish species. Utilization of the species for recreational purposes

could occur should an individual unknowingly collect the species while

gathering bait minnows for personal use.

C. Disease or Predation

When fish are forced into confined habitats due to low flow, they

are more susceptible to both disease and predation. Predation takes

place when non-native species, including northern pike (Esox lucius),

walleye (Stizostedion vitreum), white crappie (Pomoxis annularis),

white bass (Morone chrysops), black and brown bullheads (Ameiurus

melas, A. nebulosus), smallmouth bass (Micropterus dolomieui), and

largemouth bass (Micropterus salmoides) are confined, during low flow

or no flow, in limited habitat with H. amarus and other native species.

These species have been introduced primarily by State and Federal fish

and wildlife management agencies in efforts to develop sport fisheries

in reservoirs created by the mainstream dams. The species have not

remained confined to the reservoirs and have become established in the

river both upstream from the impoundments and downstream of the dams

where it is suspected they may compete with H. amarus for space and

food in addition to preying upon them. Native predatory fish species,

including the Rio Grande chub (Gila pandora) and bluegill (Lepomis

macrochirus), may also prey upon subadult H. amarus under these

circumstances. Avian and mammalian predation probably increases when H.

amarus become confined in small clear-water pools.

Confining fish to pools causes stress that can often result in

outbreaks of parasitic disease. Most notable is parasitism by the

protozoan Ichthyophthirius multifilis, which can be promoted by stress.

External parasites, such as the copepod Lernaea, are more common among

fish in confined conditions. No studies have been conducted on the

impact of disease and parasites upon H. amarus; therefore, the

significance of these threats for existing populations of the species

is not known. However, stress-induced outbreaks may be exacerbated when

high levels of pollutants or other stresses are present.

D. The Inadequacy of Existing Regulatory Mechanisms

The State of New Mexico lists H. amarus as an endangered species,

Group 2 (New Mexico Department of Game and Fish 1993), which includes

those species ``. . . whose prospects of survival or recruitment within

the State are likely to be in jeopardy within the foreseeable future.''

This listing provides the protection of the New Mexico Wildlife

Conservation Act (Section 17-2-37 through 17-2-46 NMSA 1978) and

prohibits taking of such species except under the issuance of a

scientific collecting permit. The protection afforded to the species by

the State does not provide protection to the habitat upon which the

species depends.

New Mexico water law does not include provisions for acquisition of

instream water rights for protection of fish and wildlife and their

habitats. This has been a major factor affecting the survival of

species dependent upon the presence of instream flow. Agencies

responsible for administering water rights have been unable to

administer the rights in a manner that protects, maintains, and

recovers the Rio Grande silvery minnow. Under the existing water rights

administration, two native fish species in the Rio Grande have become

extinct, and two others have been extirpated.

State Game and Fish regulations in New Mexico allow the use of live

minnows, including those brought into the State from other drainages,

for sport fishing. This practice has encouraged the spread of these

species, one of which, the plains minnow, has completely replaced and/

or hybridized with H. amarus in the Pecos River.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

In 1979, Cowley discovered the introduction of plains minnow (H.

placitus) into the Pecos River drainage, New Mexico, from collections

made as early as 1968, and also recognized the disappearance of native

H. amarus. The last known collections of H. amarus from the Pecos River

took place in 1968 near Roswell, New Mexico. These same collections

verified the first specimens of H. placitus from the river. It is

suspected, because of the widespread use of H. placitus as a commercial

bait species, that its introduction into the Pecos River was the result

of release of bait fish by anglers.

The Service has carefully assessed the best scientific and

commercial information available regarding the past, present, and

future threats faced by this species in determining to make this rule

final. Based on this evaluation, the preferred action is to list the

Rio Grande silvery minnow (Hybognathus amarus) as endangered throughout

its historic range. A decision to take no action would constitute

failure to properly classify this species pursuant to the Endangered

Species Act and would exclude it from protection of the Act. The

Service believes threatened status is not the proper classification for

the species because of the extremely limited habitat the species

presently occupies and the threats it faces. Endangered status is

appropriate because of the significantly reduced range and declining

abundance of the species, and because of the remaining threats to this

fish and its habitat. Without Federal protection, the Rio Grande

silvery minnow can be expected to become extinct in the foreseeable

future.

Critical Habitat

Section 4(a)(3) of the Act requires, to the maximum extent prudent

and determinable, that the Secretary designate critical habitat at the

time a species is determined to be endangered or threatened. Section

4(b)(6)(C) states that a concurrent critical habitat designation is not

required, and that the final decision on designation may be postponed

for 1 year from the date of publication of the final rule to list the

species. Section 4(b)(6)(C)(ii) allows the Service to delay critical

habitat designation if it is not then determinable. The Service's

regulations (50 CFR 424.12(a)(2)) state that critical habitat is not

determinable if information sufficient to perform required analyses of

the impacts of the designation is lacking or if the biological needs of

the species are not sufficiently well known to permit identification of

an area as critical habitat. Section 4(b)(2) of the Act requires the

Service to consider economic and other impacts of designating a

particular area as critical habitat. The Service is in the process of

evaluating the information obtained during the comment period on the

economic impacts of designating critical habitat, and has started the

process of having an economic analysis prepared on the proposed

critical habitat designation. The complexities and extent of the

activities that must be assessed preclude completion of the economic

analysis within the 1-year deadline for listing the species. The

completed draft economic analysis will be made available for public

review and comment. The final decision on designation of critical

habitat for the Rio Grande silvery minnow must be made by March 1,

1995, pursuant to section 4(b)(6)(C)(ii) of the Act.

Available Conservation Measures

Conservation measures provided to species listed as endangered or

threatened under the Endangered Species Act include recognition,

recovery actions, requirements for Federal protection, and prohibitions

against certain practices. Recognition through listing encourages and

results in conservation actions by Federal, State, and private

agencies, groups, and individuals. The Endangered Species Act provides

for possible land acquisition and cooperation with the States and

authorizes recovery plans for all listed species. The protection

required of Federal agencies and the prohibitions against taking and

harm are discussed, in part, below.

Section 7(a) of the Act, as amended, requires Federal agencies to

evaluate their actions with respect to any species that is proposed or

listed as endangered or threatened and with respect to its critical

habitat if any is proposed or designated. Regulations implementing this

interagency cooperation provision of the Act are codified at 50 CFR

part 402. Section 7(a)(2) requires Federal agencies to ensure that

activities they authorize, fund, or carry out are not likely to

jeopardize the continued existence of a listed species or to destroy or

adversely modify its critical habitat. If a Federal action may affect a

listed species or its critical habitat, the responsible Federal agency

must enter into formal consultation with the Service.

Federal actions that are expected to occur that may affect the

survival of H. amarus include the operation and maintenance of dams and

other structures that regulate the flow of water in the Rio Grande.

Federal agencies that serve as water managers and decision-makers who

determine timing and amount of flow in the river include the

International Boundary and Water Commission, which ensures delivery of

water to Mexico under international treaties; the Bureau of

Reclamation, which has played an important role in water development in

the middle Rio Grande and has been actively involved in the major water

supply networks of the basin; and the Corps, which is responsible for

controlling any dredging or filling within navigable waterways and

associated wetlands under section 404 of the Clean Water Act. The Corps

also has constructed and operates Abiquiu, Cochiti, Galisteo, and Jemez

dams to control flood waters and sediment in the Rio Grande. The

Environmental Protection Agency oversees water quality issues that may

affect the river. In addition, actions on the northern pueblos that are

funded, authorized, or carried out by the Bureau of Indian Affairs may

affect the Rio Grande silvery minnow.

The Act and implementing regulations found at 50 CFR 17.21 set

forth a series of general prohibitions and exceptions that apply to all

endangered wildlife. These prohibitions, in part, make it illegal for

any person subject to the jurisdiction of the United States to take

(includes harass, harm, pursue, hunt, shoot, wound, kill, trap, or

collect, or to attempt any of these), import or export, ship in

interstate commerce in the course of a commercial activity, or sell or

offer for sale in interstate or foreign commerce any listed wildlife

species. It also is illegal to possess, sell, deliver, carry,

transport, or ship any such wildlife that has been taken illegally.

Certain exceptions apply to agents of the Service and State

conservation agencies.

Permits may be issued to carry out otherwise prohibited activities

involving endangered wildlife species under certain circumstances.

Regulations governing permits are at 50 CFR 17.22 and 17.23. Such

permits are available for scientific purposes, to enhance the

propagation or survival of the species, and/or for incidental take in

connection with otherwise lawful activities. In some instances, permits

may be issued for a specified time to relieve undue economic hardship

that would be suffered if such relief were not available. This species

is not in trade, and such permit requests are not expected.

National Environmental Policy Act

The Fish and Wildlife Service has determined that an Environmental

Assessment, as defined under the authority of the National

Environmental Policy Act of 1969, need not be prepared in connection

with regulations adopted pursuant to Section 4(a) of the Endangered

Species Act of 1973, as amended. A notice outlining the Service's

reasons for this determination was published in the Federal Register on

October 25, 1983 (48 FR 49244).

References Cited

A complete list of all references cited herein, as well as

others, is available upon request from the State Supervisor, New

Mexico Ecological Services State Office (see ADDRESSES section).

Author: The primary author of this final rule is Gerald L.

Burton (see ADDRESSES section).

List of Subjects in 50 CFR Part 17

Endangered and threatened species, Exports, Imports, Reporting and

recordkeeping requirements, and Transportation.

Regulation Promulgation

PART 17--[AMENDED]

Accordingly, part 17, subchapter B of chapter I, title 50 of the

Code of Federal Regulations, is amended as set forth below:

1. The authority citation for part 17 continues to read as follows:

Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C.

4201-4245; Public Law 99-625, 100 Stat. 3500; unless otherwise

noted.

2. Amend Sec. 17.11(h) by adding the following, in alphabetical

order under ``FISHES'', to the List of Endangered and Threatened

Wildlife:

Sec. 17.11 Endangered and threatened wildlife.

* * * * *

(h) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------

Common name Vertebrate population

Species -------------------------- Historic range where endangered or Status When listed Critical Special

Scientific name threatened habitat rules

--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * * * *

Fishes

* * * * * * *

Minnow, Rio Grande Hybognathus amarus...... U.S.A. (NM, TX), Mexico. Entire.................. E 541 NA NA

silvery.

* * * * * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------

Dated: June 30, 1994.

Mollie H. Beattie

Director, Fish and Wildlife Service.

[FR Doc. 94-17576 Filed 7-19-94; 8:45 am]

BILLING CODE 4310-55-P