# Endangered and Threatened Wildlife and Plants; Removing the Oregon Chub From the Federal List of Endangered and Threatened Wildlife

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A2015-02951

## Record

- **Collection:** Federal Register
- **Document type:** Rule
- **Published:** February 19, 2015
- **Citation:** 80 FR 9126

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R1-ES-2014-0002; FXES11130900000C6-156-FF09E42000]
RIN 1018-BA28
Endangered and Threatened Wildlife and Plants; Removing the Oregon Chub From the Federal List of Endangered and Threatened Wildlife

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Final rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), are removing the Oregon chub (
Oregonichthys crameri
) from the Federal List of Endangered and Threatened Wildlife. This determination is based on a thorough review of the best available scientific and commercial information, which indicates that the Oregon chub has recovered and no longer meets the definition of an endangered species or a threatened species under the Endangered Species Act of 1973, as amended (Act). Our review of the status of this species shows that the threats to this species have been eliminated or reduced and populations are stable so that the species is not currently, and is not likely to again become, a threatened species within the foreseeable future in all or a significant portion of its range. This rule also removes the currently designated critical habitat for the Oregon chub throughout its range.

DATES:

This rule is effective on March 23, 2015.

ADDRESSES:

This final rule and the post-delisting monitoring plan are available on the Internet at
http://www.regulations.gov
at Docket Number FWS-R1-ES-2014-0002. Comments and materials received, as well as supporting documentation used in the preparation of this rule, will be available for public inspection, by appointment, during normal business hours, at the Service's Oregon Fish and Wildlife Office, 2600 SE 98th Avenue, Portland, OR 97266.

FOR FURTHER INFORMATION CONTACT:

Paul Henson, State Supervisor, Oregon Fish and Wildlife Office (see
ADDRESSES
); telephone 503-231-6179; or facsimile (fax) 503-231-6195. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Information Relay Services (FIRS) at 800-877-8339 for assistance.

SUPPLEMENTARY INFORMATION:

Executive Summary

This document contains: (1) A final rule to remove the Oregon chub from the Federal List of Endangered and Threatened Wildlife, and (2) a notice of availability of a final post-delisting monitoring plan.

Species addressed
—The Oregon chub (
Oregonichthys crameri
) is endemic to the Willamette River drainage of western Oregon. Extensive human activities in the Willamette River Basin (
e.g.,
dams, levees, and other human development within the floodplain) have substantially reduced the amount and suitability of habitat for this species. Improved floodplain management and floodplain restoration by multiple conservation partners has reduced and mitigated adverse human-related impacts and resulted in significant improvements to habitat quality and quantity. As a result, threats to the Oregon chub have been largely ameliorated.

The status of the species has improved dramatically due to the discovery of many new populations and successful reintroductions within the species' historical range. At the time of listing in 1993 (58 FR 53800, October 18, 1993), only nine known populations of Oregon chub existed, and few estimates existed of the number of individuals within each population. The locations of these populations represented a small fraction (estimated as 2 percent based on stream miles) of the species' formerly extensive distribution within the Willamette River drainage. In 2013, 77 populations were known to exist throughout the Willamette River drainage. The risk of extinction is substantially reduced as threats have been ameliorated and new populations have been discovered or established.

Purpose of the Regulatory Action
—Under the Endangered Species Act of 1973, we may be petitioned to list, delist, or reclassify a species. In 2010, we reclassified the Oregon chub from endangered to threatened (75 FR 21179, April 23, 2010), based on defined criteria in the species recovery plan. In 2014, we proposed to remove the Oregon chub from the Federal List of Endangered and Threatened Wildlife (79 FR 7136, February 6, 2014), based on delisting criteria in the recovery plan and a five factor threats analysis. Threats to this species have been largely ameliorated, with the exception of the effects of climate change, and we do not consider such effects to be a substantial threat to the species at this time. Therefore, we have determined that the Oregon chub no longer meets the definition of an endangered or threatened species under the Act. This final rule removes the Oregon chub from the Federal List of Endangered and Threatened Wildlife. This rule also removes the currently designated critical habitat for the Oregon chub throughout its range.

Basis for the Regulatory Action
—Under the Act, a species may be determined to be an endangered species or threatened species because of any of five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. We must consider the same factors in delisting a species. We may delist a species if the best scientific and commercial data indicate the species is neither endangered nor threatened for one or more of the following reasons: (1) The species is extinct; (2) the species has recovered and is no longer threatened or endangered; or (3) the original scientific data used at the time the species was classified were in error.

Threats to the Oregon chub at the time of listing in 1993, included loss of habitat, water quality, and competition with and predation by nonnative fishes. We reviewed all available scientific and commercial information pertaining to the five threat factors in our status review of the Oregon chub, and the results are summarized below.

• We consider the Oregon chub to be “recovered” because all substantial threats to this fish have been ameliorated and the species is now abundant and well-distributed throughout much of its presumed historical range.

• All remaining potential threats to the species and its habitat, with the exception of effects related to climate change, have been ameliorated, and many populations exist on public lands managed for fish and wildlife conservation.

• We do not consider effects related to climate change to be a substantial threat to the species at this time, and we do not expect climate change effects to rise to the magnitude or severity such that the species will be likely to become an endangered species within the foreseeable future. While we recognize that climate change effects such as rising air temperatures, reduced snowpack, and increased drought may have potential effects to the Oregon chub and its habitat, the best available information does not indicate that such

effects will significantly impact the Oregon chub or its habitat. We expect that the Oregon chub's susceptibility to climate change effects is low given the wide range of temperature tolerances of Oregon chub, the range and diversity of habitats occupied by the species, and because effects of climate change will be ameliorated by multiple storage dams in the Willamette River Basin.

• We find that delisting the Oregon chub is warranted and thus we are removing this taxon from the Federal List of Endangered and Threatened Wildlife.

• We prepared a final post-delisting monitoring plan to monitor the Oregon chub after delisting to verify that the species remains secure.

Previous Federal Actions

Please refer to the proposed rule to remove the Oregon chub from the Federal List of Endangered and Threatened Wildlife (79 FR 7136, February 6, 2014) for a detailed description of previous Federal actions concerning this species. This document is our final rule to remove the Oregon chub from the Federal List of Endangered and Threatened Wildlife.

Background

This is a final rule to remove the Oregon chub from the Federal List of Endangered and Threatened Wildlife. It is our intent to discuss in this final rule only those topics directly relevant to the removal of the Oregon chub from the Federal List of Endangered and Threatened Wildlife.

Species Information

The following section contains information updated from that presented in the proposed rule to remove Oregon chub from the Federal List of Endangered and Threatened Wildlife, which published in the
Federal Register
on February 6, 2014 (79 FR 7136). A thorough discussion of the species' description, population density, and abundance is also found in the proposed rule.

Species Description and Life History—
The Oregon chub is a small minnow in the Cyprinid family. Young of the year range in length from 7 to 32 millimeters (mm) (0.3 to 1.3 inches (in)), and adults grow up to 90 mm (3.5 in) in length (Pearsons 1989, p. 17). The Oregon chub reaches maturity at about 2 years of age (Scheerer and McDonald 2003, p. 78) and in wild populations can live up to 9 years. Oregon chub spawn from May through August and are not known to spawn more than once a year.

The Oregon chub live in slack water off-channel habitats such as beaver (
Castor canadensis
) ponds, oxbows, side channels, backwater sloughs, low-gradient tributaries, and flooded marshes. These habitats usually have little or no water flow, are dominated by silty and organic substrate, and contain considerable aquatic vegetation providing cover for hiding and spawning (Pearsons 1989, p. 27; Markle
et al.
1991, p. 289; Scheerer and McDonald 2000, p. 1). The average depth of habitat used by the Oregon chub is less than 1.8 meters (m) (6 feet (ft)), and summer water temperatures typically exceed 16 degrees Celsius (61 degrees Fahrenheit). Adult Oregon chub seek dense vegetation for cover and frequently travel in the mid-water column in beaver channels or along the margins of aquatic plant beds. Larval Oregon chub congregate in shallow near-shore areas in the upper layers of the water column, whereas juveniles venture farther from shore into deeper areas of the water column (Pearsons 1989, p. 16). In the winter months, Oregon chub are found buried in the detritus or concealed in aquatic vegetation (Pearsons 1989, p. 16). Fish of similar size school and feed together. In the early spring, Oregon chub are most active in the warmer, shallow areas of aquatic habitats.

The Oregon chub is an obligatory sight feeder (Davis and Miller 1967, p. 32). It feeds throughout the day and stops feeding after dusk (Pearsons 1989, p. 23). The Oregon chub feeds mostly on water column fauna. The diet of Oregon chub adults collected in a May sample consisted primarily of minute crustaceans including copepods, cladocerans, and chironomid larvae (Markle
et al.
1991, p. 288). The diet of juvenile Oregon chub also consisted of minute organisms such as rotifers and cladocerans (Pearsons 1989, p. 2).

Range—
The Oregon chub is endemic to the Willamette River drainage of western Oregon. Historical records show the Oregon chub existed as far downstream as Oregon City and as far upstream as the town of Oakridge. Historically a dynamic, alluvial river, the Willamette and its tributaries created broad floodplains and braided reaches with many side channels, sloughs, and other similar slack-water habitats that support the Oregon chub. The Willamette is typical of river systems on the west side of the Cascade Mountains, with the largest river flows/floods influenced by heavy rain, or rain-on-snow events during the late winter and spring. Snowmelt in the spring typically produces an elongated flow peak in the spring, with decreasing flows throughout summer.

Extensive human activities in the Willamette River Basin have substantially reduced the floodplain habitats and altered water temperatures, as well as the timing, duration, and magnitude of floods in the basin. In the 1950s and 1960s, the U.S. Army Corps of Engineers (USACE) constructed 13 large dams on many of the tributaries of the Willamette River, with the primary purpose of flood risk reduction. Though the Willamette River mainstem and some tributaries remain undammed, miles of levees have also been constructed to further increase agricultural and urban use of these former floodplain areas.

At the time of listing in 1993 (58 FR 53800, October 18, 1993), only nine known populations of Oregon chub existed, and few estimates existed of the number of individuals within each population. The locations of these populations represented a small fraction (estimated as 2 percent based on stream miles) of the species' formerly extensive distribution within the Willamette River drainage.

Abundance and Distribution
—Since we listed the Oregon chub as endangered in 1993, the status of the species improved dramatically due to the discovery of many new populations and successful reintroductions within the species' historical range (Scheerer 2007, p. 97). Recently, since we reclassified the Oregon chub to threatened status in 2010 (75 FR 21179, April 23, 2010), a substantial number of new Oregon chub populations were discovered (34 populations) and established through introductions (8 populations). In 2013, the Oregon Department of Fish and Wildlife (ODFW) confirmed the existence of Oregon chub at 77 locations in the Molalla River, Luckiamute River, North and South Santiam River, McKenzie River, Middle Fork and Coast Fork Willamette Rivers, and several tributaries to the mainstem Willamette River downstream of the Coast Fork and Middle Fork Willamette River confluence (Bangs
et al.
2012, pp. 7-9), including 56 naturally occurring and 21 introduced populations. In 2013, the estimated abundance of 41 Oregon chub populations was greater than 500 fish each, and 23 of these populations exhibited a stable or increasing trend over the last 7 years (Bangs
et al.
2013, p. 1). The current status of Oregon chub populations meets the goals of the species recovery plan for delisting. The distribution of these sites is shown in Table 1.

Table 1—Distribution of Oregon Chub Populations Meeting Recovery Criteria for Delisting

[Bangs
et al.
2013, pp. 5-8]

Recovery subbasin

Number of
populations

Number of large populations
(≥500 adult fish)

Number of large populations with
stable/increasing abundance trend

Total estimated abundance in subbasin

Santiam
19
13
7
32,714

Mainstem Willamette
1

26
10
6
71,840

Middle Fork Willamette
28
17
10
54,285

Coast Fork Willamette
2

4
1
0
824

Total
77
41
23
159,663

1
Includes McKenzie River subbasin.

2
The Coast Fork Willamette was identified as a subbasin containing Oregon chub in the recovery plan, but was not identified as a Recovery Area.

Although certain populations of the Oregon chub remain relatively stable from year to year, we observed substantial fluctuations in abundance within populations. For instance, the largest known population at Ankeny National Wildlife Refuge was 21,790 Oregon chub individuals in 2010, and increased to 96,810 in 2011. The population then declined from 82,800 to 47,920 between 2012 and 2013. We observed similar substantial fluctuations in 2013, at the Dunn Wetland and at the Hills Creek Pond populations. While substantial, these fluctuations commonly occur, and appear natural and cyclical. For example, we estimated the population abundance at the Dexter Reservoir Alcove “PIT1” site at 140 in 1995. Although annual estimated abundance fluctuated, this population reached 1,440 estimated individuals in 2000. The population then declined to 70 individuals in 2004, and then increased again to reach 1,370 estimated individuals in 2009 (Scheerer
et al.
2005, p. 2).

A major component of recovery efforts for the Oregon chub was introducing the species into hydrologically isolated habitats that are free from nonnative fish species. Twenty-one new populations were established since 1988 (Table 2). In 2013, 14 introduced populations existed with more than 500 Oregon chub each; 6 of these populations exhibited a stable or increasing 7-year abundance trend (Bangs
et al.
2013, p. 14).

Table 2—Introduced Oregon Chub Populations

[Bangs
et al.
2013, pp. 6-8, 15]

[MS—Mainstem Willamette River, S—Santiam River, CF—Coast Fork Willamette River, and MF—Middle Fork Willamette River]

Site name
Subbasin

Year of first
introduction

Number of fish introduced

Estimated abundance
(2013)

Dunn Wetland
MS
1997
573
6,439

Finley Display Pond
MS
1998
500
118

Russell Pond
MS
2001
500
133

Finley Cheadle Pond
MS
2002
530
157

Ankeny Willow Marsh
MS
2004
500
47,920

St. Paul Ponds
MS
2008
195
442

Finley-Buford Pond
MS
2011
160
1,009

Murphy Pond
MS
2011
214
1,079

Ellison Pond
MS
2012
110
9

McCrae Reservoir
MS
2013
29
29

Foster Pullout Pond
S
1999
500
3,412

South Stayton Pond
S
2006
439
1,102

North Stayton Pond
S
2010
620
3,724

Budeau South Pond
S
2010
312
2,810

Budeau North Pond
S
2010
310
8,350

Herman Pond
CF
2002
400
184

Sprick Pond
CF
2008
65
608

Wicopee Pond
MF
1992
178
4,375

Fall Creek Spillway Ponds
MF
1996
500
9,107

Haws Enhancement Pond
MF
2009
133
788

Hills Creek Pond
MF
2010
1,127
14,613

Genetic Diversity
—The Service's Abernathy Fish Technology Center conducted a genetic analysis on the Oregon chub in 2010 (DeHaan
et al.
2010, 2012, entire). The analysis examined genetic diversity at 10 microsatellite loci within and among 20 natural and 4 introduced populations. The findings suggest that four genetically distinct groups of the Oregon chub exist, corresponding to the four subbasins of the Willamette River. Levels of genetic diversity were high across the range of the species and equal to, or greater than, other threatened or endangered species of minnows (
i.e.,
cyprinids). In addition, the levels of genetic diversity for Oregon chub were similar to the creek chub
Semotilus atromaculatus,
a widespread and abundant species of minnow (DeHaan 2012, pp. 548-549). Despite fluctuations in population abundance of Oregon chub, genetic diversity remained stable

over a 7- to 8-year interval (three to four Oregon chub generations). Two populations of the 24 evaluated had reduced genetic diversity: A recent bottleneck was observed in the Shetzline population, and the Geren Island population showed evidence of decreasing diversity, possibly due to reductions in the population size from 8,660 to 360 fish between 1997 and 2000 (Bangs
et al.
2012, p. 109). Currently, both populations are abundant and exhibit an increasing trend in population growth over the last 7 years (Bangs
et al.
2013, pp. 7
-
8).

The genetic assessment (DeHaan
et al.
2010, p. 18; DeHaan
et al.
2012, p. 545) shows that the current Oregon chub translocation guidelines (ODFW 2006, entire) (which require the donor population from within same subbasin, and a minimum of 500 Oregon chub introduced) are effective in establishing genetically viable populations. Levels of genetic diversity were similar to natural populations in three out of four of the introduced sites studied. Introduced populations from multiple sources had increased diversity and showed evidence of interbreeding. The Dunn wetland population, which had three donor populations, had the highest genetic diversity of all sites (natural and introduced). The Wicopee Pond population had relatively low levels of genetic diversity, which was likely because this population was founded with only 50 Oregon chub originating from 1 source population. These data support introducing greater numbers of individuals and using multiple sources from within a subbasin.

Recovery and Recovery Plan Implementation

Background—
Section 4(f) of the Act (16 U.S.C. 1531
et seq.
) directs us to develop and implement recovery plans for the conservation and survival of endangered and threatened species unless we determine that such a plan will not promote the conservation of the species. Under section 4(f)(1)(B)(ii), recovery plans must, to the maximum extent practicable, include: “Objective, measurable criteria which, when met, would result in a determination, in accordance with the provisions of [section 4 of the Act], that the species be removed from the list.” However, revisions to the list (adding, removing, or reclassifying a species) must reflect determinations made in accordance with sections 4(a)(1) and 4(b) of the Act. Section 4(a)(1) requires that the Secretary determine whether a species is endangered or threatened (or not) because of one or more of five threat factors. Section 4(b) of the Act requires that the determination be made “solely on the basis of the best scientific and commercial data available.” Therefore, recovery criteria should help indicate when we would anticipate that an analysis of the five threat factors under section 4(a)(1) would result in a determination that the species is no longer an endangered species or threatened species because of any of the five statutory factors (see Summary of Factors Affecting the Species).

While recovery plans provide important guidance to the Service, States, and other partners on methods of minimizing threats to listed species and measurable objectives against which to measure progress towards recovery, they are not regulatory documents and cannot substitute for the determinations and promulgation of regulations required under section 4(a)(1) of the Act. A decision to revise the status of or remove a species from the Federal List of Endangered and Threatened Wildlife (50 CFR 17.11) is ultimately based on an analysis of the best scientific and commercial data then available to determine whether a species is no longer an endangered species or a threatened species, regardless of whether that information differs from the recovery plan.

Recovery plans may be revised to address continuing or new threats to the species, as new, substantive information becomes available. The recovery plan identifies site-specific management actions that will achieve recovery of the species, measurable criteria that set a trigger for review of the species' status, and methods for monitoring recovery progress. Recovery plans are intended to establish goals for long-term conservation of listed species and define criteria that are designed to indicate when the substantial threats facing a species have been removed or reduced to such an extent that the species may no longer need the protections of the Act.

There are many paths to accomplishing recovery of a species, and recovery may be achieved without all criteria being fully met. For example, one or more criteria may be exceeded while other criteria may not yet be accomplished. In that instance, we may determine that the threats are minimized sufficiently and the species is robust enough to delist. In other cases, recovery opportunities may be discovered that were not known when the recovery plan was finalized. These opportunities may be used instead of methods identified in the recovery plan. Likewise, information on the species may be discovered that was not known at the time the recovery plan was finalized. The new information may change the extent to which criteria need to be met for recognizing recovery of the species. Recovery of a species is a dynamic process requiring adaptive management that may, or may not, fully follow the guidance provided in a recovery plan.

Recovery Planning—
The Oregon Chub Working Group, which was formed prior to listing the species, is a proactive force in improving the conservation status of the Oregon chub. This group of Federal and State agency biologists, academicians, land managers, and others has met each year since 1991, to share information on the status of the Oregon chub, results of new research, and ongoing threats to the species. Additionally, an interagency conservation agreement was established for the Oregon chub in 1992 (ODFW
et al.
1992). The objectives of the agreement were to: (1) Establish a task force drawn from participating agencies to oversee and coordinate Oregon chub conservation and management actions; (2) protect existing populations; (3) establish new populations; and (4) foster greater public understanding of the species, its status, and the factors that influence it (ODFW
et al.
1992, pp. 3-5). These objectives are similar to that of the subsequently developed recovery plan.

The Recovery Plan for the Oregon Chub was approved by the Service on September 3, 1998 (Service 1998). The recovery plan outlines recovery criteria to assist in determining when the Oregon chub has recovered to the point that the protections afforded by the Act are no longer needed. These delisting criteria are: (1) 20 populations of at least 500 individuals each are established and maintained; (2) all of these populations must exhibit a stable or increasing trend for 7 years; (3) at least 4 populations (meeting criteria 1 and 2) must be located in each of the 3 subbasins (Mainstem Willamette, Middle Fork Willamette, and Santiam Rivers); and (4) management of these 20 populations must be guaranteed in perpetuity (Service 1998, pp. 27-28).

Recovery Plan Implementation—
The status of the Oregon chub has improved dramatically since it was listed as endangered. The improvement is due largely to the implementation of actions identified in the interagency conservation agreement and the Oregon chub recovery plan. These actions include the establishment of additional populations via successful introductions within the species' historical range and the discovery of many new populations as a result of the ODFW's surveys of the basin (Scheerer 2007, p. 97). Over 20

years have passed since the species was listed, and it is now abundant and well-distributed throughout much of its presumed historical range. Currently, there are 77 Oregon chub populations, of which 41 have more than 500 adults (Bangs
et al.
2013, pp. 5-11). The risk of extinction is substantially reduced as threats have been ameliorated and new populations have been discovered or established. The following criteria for delisting the Oregon chub are met or exceeded as described in the recovery plan:

Delisting Criterion 1: 20 populations of at least 500 individuals are established and maintained.
This criterion was exceeded; in 2013, we identified 41 populations with more than 500 adult Oregon chub (see Table 1, above).

Delisting Criterion 2: All of these populations (20) must exhibit a stable or increasing trend for 7 years.
This criterion was met. Currently, 23 populations of at least 500 individuals exhibit a stable or increasing trend for 7 years (see Table 1, above).

Delisting Criterion 3: At least four populations (meeting criteria 1 and 2) must be located in each of the three subbasins (Mainstem Willamette, Middle Fork, and Santiam Rivers).
This criterion was exceeded in all three subbasins. Six populations in the Mainstem Willamette River subbasin, 10 populations in the Middle Fork Willamette River subbasin, and 7 populations in the Santiam River subbasin meet the first 3 delisting criteria (see Table 1, above).

Delisting Criterion 4: Management of these 20 populations must be guaranteed in perpetuity.
The level of management protection recommended in the Oregon chub recovery plan (
i.e.,
management guaranteed into perpetuity) exceeds the requirements of the Act in evaluating whether a species meets the statutory definition of endangered or threatened, as adequate protection for the species in the long term may be provided otherwise. Although we do not have guarantees that all of the populations will be managed into perpetuity, we have a high level of confidence that management of the Oregon chub sites will continue to provide adequate protection for the species in the long term, as further discussed below. Of the 41 sites with populations of more than 500 Oregon chub, 28 of the sites are in public or Tribal ownership, with either active conservation management programs, or practices where land managers consider the needs of the Oregon chub when implementing site management activities. Additionally, eight of the sites with abundant populations of the Oregon chub are on land that is privately owned, either where landowners have signed conservation agreements or are enrolled in our Safe Harbor Program. Three additional sites are on land that is in a permanent easement or ownership by the McKenzie River Trust, a land trust dedicated to conservation of wetland and riparian habitat.

Based on our review of the Oregon chub recovery plan, we conclude that the status of the species has improved due to implementation of recovery activities and the objectives of the recovery plan have been met. Our analysis of whether the species has achieved recovery and thus no longer requires the protections of the Act because it is no longer an endangered or threatened species is based on the five statutory threat factors identified in section 4 of the Act, and discussed below in the Summary of Factors Affecting the Species.

Summary of Comments and Recommendations

In the proposed rule published February 6, 2014 (79 FR 7136), we requested that all interested parties submit written comments on the proposal by April 7, 2014. We also contacted appropriate Federal and State agencies, scientific experts and organizations, and other interested parties and invited them to comment on the proposal. The Service hosted a media event with local and national news coverage announcing the proposed rule on February 4, 2014. We did not receive any requests for a public hearing.

During the comment period for the proposed rule, we received five comment letters (three from peer reviewers, one from the ODFW, and one from the public) directly addressing the proposed removal of the Oregon chub from the Federal List of Endangered and Threatened Wildlife. All substantive information provided during the comment period is either incorporated directly into this final determination or is addressed below. The following section summarizes issues and information we consider to be substantive from peer review and public comments, and provides our responses.

Peer Review

In accordance with our policy, “Notice of Interagency Cooperative Policy for Peer Review in Endangered Species Act Activities,” which was published on July 1, 1994 (59 FR 34270), we solicited expert opinion on the proposed rule and the draft post-delisting monitoring plan from three knowledgeable independent individuals with scientific expertise that included familiarity with Oregon chub and its habitat, biological needs, recovery efforts, and threats. We received responses from all three peer reviewers. Issues and information provided by the peer reviewers are summarized in the
Peer Reviewer Comments
section, and where they overlap with similar issues identified by the public, they are included in the
Public Comments
section.

Peer Reviewer Comments

Comment (1):
Two peer reviewers suggested that the lower bounds of the confidence intervals should be used to determine the number of populations meeting Delisting Criterion #1.

Our response:
The species' recovery plan does not define the method to determine population size for Delisting Criterion #1. The ODFW uses a single-sample mark-recapture model, also called an adjusted Petersen estimate, to estimate population abundance (Bangs
et al.
2013, p. 5). This method is supported in the literature (Seber 1973, pp. 59-60, Ricker 1975, pp. 75-79), and demonstrates reliable estimates for sampling conditions similar to what ODFW experiences monitoring Oregon chub. The ODFW also demonstrates the reliability in its population abundance estimates by providing a 95 percent confidence interval (Bangs
et al.
2013, pp. 9-12). The calculation of the confidence interval is highly influenced by the sample size; a narrower interval requires sampling more individuals (Seber 1973, p. 61). Thus, in small populations, greater sampling effort would be required to demonstrate if a population met Delisting Criterion #1 if the lower bound was used, thus exposing more individuals to the risk of trapping or handling mortality. We do not agree with the reviewer's suggestion to use the lower bound of the 95 percent confidence interval, as this method exposes individuals in small populations to greater risk of mortality than the method used by the ODFW.

Comment (2):
One peer reviewer asked why the Coast Fork Willamette Oregon chub populations were not mentioned under Delisting Criterion #3.

Our response:
Under the recovery plan for Oregon chub, the Coast Fork Willamette was not included in the Mainstem, Santiam, or Middle Fork Willamette recovery areas. The recovery plan states: “Although a single small population of Oregon chub currently occurs in a fourth subbasin, the Coast Fork, recovery efforts will not focus on this subbasin because surveys have not

revealed any other suitable habitats, and nonnative fish are very common.” Although we are encouraged that two additional, small populations of Oregon chub were discovered and two introduced populations were established in the Coast Fork subbasin, recovery criteria were met without the inclusion of the populations in this subbasin.

Comment (3):
One peer reviewer asked that the Service provide a more current summary of the 2009-2010 Willamette Floodplain Report (Bangs
et al.
2011a, entire). This peer reviewer also suggested that the delisting rule incorporate 2013 data.

Our response:
The Willamette Floodplain Report, with analysis of data from 2009-2012, is currently in preparation by the ODFW, and is expected to be available late spring 2015 at the earliest. As such, we are using the best available information at this time. We agree with the second part of this comment, and updated the rule to include the 2013 data.

Public Comments

Comment (4):
One commenter stated that the Service did not adequately consider effective population size in the decision to delist the Oregon chub. The commenter stated that the general rule for short-term (50) and long-term (500) effective population size is not appropriate, as an effective population size of 500 individuals does not sufficiently reduce extinction risk. The commenter stated that determining a minimum viable population based on effective population size should include additional factors, such as environmental and demographic stochasticity, spatial dispersion, overlapping generations, and synergistic interactions among the risk factors. As an example, the commenter mentioned that the largest population of Oregon chub in the Middle Fork Willamette subbasin is in Hills Creek Pond; the population abundance was estimated at 13,460 individuals in 2012. The commenter noted that this was the total population size and not the effective population size, and was too small to assure viability.

Our response:
The minimum viable population is the smallest estimated population size with a high probability of long-term persistence. Minimum viable population factors in risks associated with demographic and environmental stochastic events, and the impacts of inbreeding and limited genetic diversity. The effective population size is the number of breeding individuals in the population that contribute genetic material to the next generation, and can be used to determine the impacts of inbreeding and limited genetic diversity during the analysis of the minimum viable population. The recovery criteria in the recovery plan (Service 1998) do not require measuring effective population sizes for Oregon chub. At the time the recovery plan was written, the Service used the best available science to set the recovery criterion abundance threshold at 500 adult fish per population. This threshold is based on the total adult population size, not effective population size, and takes into account effects of limited genetic diversity and inbreeding associated with small population size and the risk associated with stochastic events.

Jamieson and Allendorf (2012, p. 583) suggested that, at a minimum, an effective population size of 500 individuals is needed for conservation of endangered species, including the potential impacts of stochastic events on conservation genetics. Jamieson and Allendorf (2012, p. 580) suggested an effective population size of 500 individuals is the total for all populations of a species, and not the size of individual populations. The total Oregon chub population size in 2013 was approximately 160,000 adult fish (Bangs
et al.
2013, pp. 6-9).

DeHaan (2012, p. 543) determined effective population size for three isolated Oregon chub populations as part of a genetic analysis of the species. While these isolated populations represent a worst-case scenario for negative genetic effects, the study suggested: (1) There was no immediate threat from inbreeding or genetic drift, and (2) many Oregon chub populations have some degree of connectivity to other populations. This study also determined that genetic diversity remains high and stable over time, despite fluctuations in individual population size. Further, the ODFW (Bangs
et al.
2013, p. 17) documented movement of individual Oregon chub between populations, which provides a mechanism for genetic exchange between populations that will maintain genetic variation (DeHaan 2012, p. 543). Despite the recent genetic analysis (DeHaan 2012, p. 543), the best available information is not sufficient to determine a minimum viable population size for Oregon chub.

In our decision to delist the Oregon chub, we are required to analyze the current or foreseeable threats to the species to determine whether a species meets the definition of endangered or of threatened, based on the best available scientific information. Our analysis includes recent genetic data that demonstrate Oregon chub are not threatened by low genetic diversity. We conclude that the recovery criterion abundance threshold of 500 adult fish per population is adequate, and analyzing the effective population size or determining the minimum viable population is not required in order to assess the status of the species.

Comment (5):
One commenter stated that the Service was not conservative in the analysis of population size and must err on the side of caution. The reviewer commented that stochastic events and small population sizes decreases the population viability and increases the extinction risk of Oregon chub. The commenter further stated that the extreme annual variability within individual Oregon chub population sizes suggests considerable risk of extinction, even in locally abundant populations. The commenter mentioned that in addition, population growth is impacted by demographic stochasticity.

Our response:
We disagree. The Act does not require that we “err on the side of caution” in determining the status of a species; it requires that we determine, based on the best available scientific information, whether a species meets the definition of endangered or of threatened. The Willamette River floodplain where Oregon chub evolved has always been highly dynamic. Oregon chub are extremely well adapted to surviving stochastic events. For instance, Oregon chub habitats have been known to freeze each winter, experience high magnitude flood flows in the spring, and reach in excess of 25 degrees Celsius (77 degrees Fahrenheit) in the summer, yet Oregon chub survive. Oregon chub are now well-distributed throughout their historical range in a variety of habitats, which reduces the risk of effects of severe stochastic events to the species throughout its range. Each habitat is impacted by stochastic effects in different ways. For example, while populations in shallow water habitats with high solar exposure may be impacted by severe hot and dry weather that raises temperatures to unsuitable levels for chub, populations in habitats that are deep and well-shaded may benefit by water warmed to the preferred temperature range for the species. Oregon chub have been documented in new, suitable habitat created by floodplain processes in the McKenzie River subbasin, and voluntary movement of Oregon chub was documented between populations in the Middle Fork Willamette River (Bangs
et al.
2012, p. 19) and McKenzie River subbasins (Bangs
et al.
2013, p. 17). These findings demonstrate the ability

of Oregon chub to colonize new habitats, resulting in exchange of genetic material between established populations, thus reducing the potential effects of stochastic events on small populations.

Further, for each “stable” population (as defined in the recovery plan), we calculate the coefficient of variation for the past 7 years. If the coefficient of variation is greater than one (in other words, if the variation is greater than the mean abundance), we consider the population “unstable” and do not consider that population to meet the recovery criteria. The 20 populations in 2012, and 23 populations in 2013, that met delisting criteria had either a “stable” or “increasing” abundance trend. This leads us to conclude that the variability in population abundance is not a factor that will impact future survival of these populations, provided the abundance criteria (500 adult fish) is met, because genetic diversity remains high and stable over time, despite fluctuations in individual population size (DeHaan 2012, p. 543). Overall, trend analysis conducted since 1996 demonstrates that the Oregon chub populations are stable and that the concerns raised by the commenter are not affecting Oregon chub recovery and are not expected into the foreseeable future.

Comment (6):
One commenter and one peer reviewer suggested including a better description of population trends for Oregon chub populations that are coexisting with nonnative predators. One peer reviewer also suggested that the Service discuss specific predators that may impact Oregon chub, instead of combining all nonnatives, specifically western mosquitofish (
Gambusia affinis
) and largemouth bass (
Micropterus salmoides
). One peer reviewer suggested that the Service include western mosquitofish as a potential predator on larval Oregon chub, and that we include this species in the predation discussion. One commenter recommended that efforts to limit largemouth bass colonization should be discussed in the final rule to delist Oregon chub. The peer reviewer asked that the Service explore alternative management of mosquitoes by using native minnows instead of nonnative western mosquitofish. One commenter stated that the inadequacy of existing regulatory mechanisms to prevent spread of western mosquitofish and largemouth bass into connected watersheds was not adequately analyzed, and should be discussed. Additionally, one peer reviewer recommended that the post-delisting monitoring (PDM) plan focus on specific nonnative species of concern (mosquitofish and largemouth bass).

Our response:
The best available data show no relationship between the presence of nonnative fish and Oregon chub population abundance trends (Bangs
et al.
2013, p. 17). Thirteen of the 23 populations that met delisting criteria with either a stable or increasing abundance trend in 2013 occur with nonnative fish; 1 of the 2 populations that had a declining abundance trend occurs with nonnative fish (Bangs
et al.
2013, p. 17). Nonnative fish that are thought to have the potential to impact Oregon chub populations through predation and competition include largemouth bass, smallmouth bass (
Micropterus dolomieu
), bluegill (
Lepomis macrochirus
), pumpkinseed sunfish (
Lepomis gibbosus
), warmouth (
Lepomis gulosus
), green sunfish (
Lepomis cyanellus
), yellow perch (
Perca flavescens
), walleye (
Sander vitreus
), black crappie (
Pomoxis nigromaculatus
), white crappie (
Pomoxis annularis
), common carp (
Cyprinus carpio
), brown bullhead (
Ameiurus nebulosus
), yellow bullhead (
Ameiurus natalis
), and western mosquitofish (Markle
et al.
1991, p. 91). We agree that western mosquitofish are potential predators on larval Oregon chub, and we have included an analysis of their impact in this final rule. While we acknowledge that some of these fish species may represent a larger threat to individual Oregon chub populations than others, we maintain that monitoring should include all nonnative species. We determine in the five factor analysis (see Factors A, C, and E) that the threats of nonnative fish to the Oregon chub have been ameliorated; thus, there is no existing or potential future significant threat that is inadequately addressed through existing regulatory mechanisms (see Factor D). Additionally, a regulatory mechanism is in place to prevent the translocation of nonnative fish. Within the State of Oregon, it is unlawful to transport, release, or attempt to release any live fish into the waters of this State (Oregon Administrative Rules (OAR) 635-007-0600). Abiotic factors such as water flow through connected habitats and variability in water temperature and depth keep largemouth bass and nonnative predators from becoming dominant in these habitats. Through the PDM, the ODFW will continue to monitor Oregon chub populations that are thriving, despite the presence of nonnative fish, to better understand the factors that allow this to occur. While we support efforts to limit the proliferation of nonnative fish in the Willamette River Basin, creating a management action for nonnative fish or addressing vector control guidelines is outside the scope of this rule and the PDM plan.

Comment (7):
Two peer reviewers and one public commenter discussed the need to consider the effects of climate change, environmental stochasticity, human population growth, and resulting changes in water availability on the viability and vulnerability of Oregon chub populations and suitable habitats. Primary concerns included effects to Oregon chub from: Extreme climatic variation (including drought effects, effects to instream flows, and increased reservoir drawdown); water temperature increases and reduced cool water refugia; the potential reduction in habitat size and quality; habitat fragmentation; and likely increases in populations of predatory and competitor nonnative fish species.

Our response:
The Service reviews the best scientific and commercial information available when conducting a threats analysis. In considering what factors might constitute a threat we must look beyond the mere exposure of the species to the factor to determine whether the exposure causes actual impacts to the species. The mere identification of factors that could negatively impact a species is not sufficient to compel a finding that listing (or maintaining a currently listed species on the Federal Lists of Endangered or Threatened Wildlife or Plants) is appropriate. We require evidence that these factors are operative threats currently acting on the species to the point that the species meets the definition of endangered or of threatened under the Act.

The Service acknowledges that environmental changes could occur over the next several decades due to both climate change effects and human population growth. However, it is difficult to: (1) Predict with any certainty how those changes may influence Oregon chub populations and their habitats in the Willamette Valley, and (2) accurately describe and assess the net effects when considering the potential negative consequences together with the potential positive consequences to Oregon chub populations. Additional information and explanation was added to this final rule in the section on “Effects Related to Climate Change” (see Factor A).

Comment (8):
One commenter stated that if Oregon chub are delisted, the terms and conditions required under the Service's biological opinion issued under section 7 of the Act to the USACE and other Federal agencies on the

continued operation and maintenance of dams in the Willamette River Basin will no longer be required, thereby removing key protections for the Oregon chub. This commenter also expressed a concern that delisting will eliminate consultation and agency review of actions permitted via the USACE permit program.

Our response:
Since 2002, the USACE has implemented minimum dam outflow targets that sustain downstream floodplain habitat, which has reduced the threat of habitat loss for the Oregon chub. These minimum flow targets will continue to be required into the future, even after the Oregon chub is delisted, under existing biological opinions from the Service and National Marine Fisheries Service (NMFS) on the USACE's Willamette Valley Project (Service 2008b, pp. 40-51; NMFS 2008, pp. 2-43 to 2-52), because these biological opinions apply to other listed fish species (Upper Willamette spring chinook salmon (
Oncorhynchus tshawytscha
), Upper Willamette winter steelhead (
Oncorhynchus mykiss
), and bull trout (
Salvelinus confluentus
)). The USACE also has a memorandum of understanding (MOU) with The Nature Conservancy's (TNC) Sustainable Rivers Project, an ongoing collaboration to promote ecologically sustainable flows below USACE dams in the Willamette River Basin (USACE and TNC 2000, 2011; entire). For these reasons, we anticipate that the USACE will continue to meet these minimum flow targets after delisting of the Oregon chub. Also, the acquisition of floodplain habitat for long-term conservation and restoration, including off-channel locations preferred by the Oregon chub, has gained momentum in the Willamette River Basin by a variety of Federal, State, Tribal, local governmental, and nongovernmental agencies, which provides assurances that Oregon chub habitat will continue to be managed for the species. Given the MOU between the USACE and TNC regarding the Sustainable Rivers Project, and the minimum flows required under two existing biological opinions (NMFS 2008, pp. 2-43 to 2-52; Service 2008b, pp. 40-51) for bull trout, Upper Willamette spring chinook, Upper Willamette winter steelhead, and their designated critical habitats, we anticipate that flow management trending towards natural flow regimes below Willamette Project dams will continue to create and rejuvenate off-channel habitats to the benefit of the Oregon chub into the foreseeable future.

The USACE permits in-water work including construction and dredging in navigable waters under section 404 of the Clean Water Act (CWA; 33 U.S.C. 1251
et seq.
). While we acknowledge that consultation under section 7 of the Act will no longer be required for Oregon chub, the Service will continue to provide comments to the USACE on individual section 404 permits in the Willamette Valley through our authorities under the Fish and Wildlife Coordination Act (16 U.S.C. 661
et seq.
). The USACE routinely sends the Service individual permit applications for our review, and we provide specific comments and recommendations to reduce negative effects to fish and wildlife, including unlisted species. For most section 404 projects, any potential negative impacts to habitat and species are generally short-term. While in-water work has the potential to impact individual Oregon chub populations, this impact for the overall population is considered a low risk because the species is widely distributed across multiple subbasins with many abundant populations. In the past 4 years, we have received approximately 13 such requests to review section 404 permits from the USACE. Of those 13 projects, we found that 9 were not likely to adversely affect Oregon chub and 2 projects only required technical assistance; we completed 1 formal consultation for a river restoration study that only anticipated short-term effects and long-term benefits. The last project was an emergency consultation when the USACE had to take action to maintain water levels in Oregon chub habitat on their property, as the habitat was affected by atypical, unexpected operations necessary for dam safety. The USACE worked with the ODFW to introduce Oregon chub into Hills Creek Pond during the drawdown as a back-up to the Dexter RV Park Pond “DEX3” and the Dexter Reservoir Alcove “PIT1” populations, in case either population failed during the drawdown.

Comment (9):
One commenter stated that there are no regulatory mechanisms to protect Oregon chub habitat in the floodplain habitats that have been acquired for long-term conservation and restoration.

Our response:
We disagree. One of the factors identified as a threat to Oregon chub at the time of listing was habitat loss. This threat has been ameliorated by the actions of multiple conservation partners over the last 20 years. In 2010, the Bonneville Power Administration (BPA) and the State of Oregon signed the Willamette River Basin Memorandum of Agreement Regarding Wildlife Habitat Protection and Enhancement (BPA and ODFW 2010, entire). The Agreement established goals for mitigating the effects of the construction, inundation, and operation of the Willamette River Basin Flood Control Projects in the Willamette Valley. Under the terms of the Agreement, the State of Oregon and the BPA agreed to acquire at least an additional 16,880 acres (ac) (6,831 hectares (ha)) of wildlife mitigation property to protect 26,537 ac (10,739 ha) (or more) by the end of 2025. Throughout the Willamette River Basin, floodplain properties have been, and will continue to be, acquired. All habitat acquisitions funded by the BPA must include provisions for permanent protections and enforcement of those protections. The acquisition of floodplain habitat for long-term conservation and restoration through these mechanisms provides assurances that Oregon chub habitats will continue to be managed for the species into the foreseeable future.

Summary of Factors Affecting the Species

This section contains updated information and associated analysis from that presented in the proposed rule (79 FR 7136, February 6, 2014). Updated information includes data collected during the 2013 field season (Bangs
et al.
2013, entire) and additional information requested by peer and public reviewers.

Section 4 of the Act and its implementing regulations (50 CFR part 424) set forth the procedures for listing species, reclassifying species, or removing species from listed status. “Species” is defined by the Act as including any species or subspecies of fish or wildlife or plants, and any distinct vertebrate population segment of fish or wildlife that interbreeds when mature (16 U.S.C. 1532(16)). 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) of the Act: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. We must consider these same five factors in delisting a species. We may delist a species according to 50 CFR 424.11(d) if the best available scientific and commercial data indicate that the species is neither endangered nor threatened for the following reasons: (1) The species is extinct; (2) the species has recovered and is no longer endangered or threatened (as is the case with the Oregon chub); and/or (3) the

original scientific data used at the time the species was classified were in error.

A recovered species is one that no longer meets the Act's definition of endangered or of threatened. Determining whether the status of a species has improved to the point that it can be delisted or downlisted requires consideration of whether the species is endangered or threatened because of the same five categories of threats specified in section 4(a)(1) of the Act. For species that are already listed as endangered or threatened, this analysis of threats is an evaluation of both the substantial threats currently facing the species and the threats that are reasonably likely to affect the species in the foreseeable future following the delisting or downlisting and the removal or reduction of the Act's protections.

A species is an “endangered species” for purposes of the Act if it is in danger of extinction throughout all or a “significant portion of its range” and is a “threatened species” if it is likely to become endangered within the foreseeable future throughout all or a “significant portion of its range.” The word “range” in the significant portion of its range phrase refers to the range in which the species currently exists. For the purposes of this analysis, we will first evaluate whether the currently listed species, the Oregon chub, should be considered endangered or threatened throughout all its range. Then we will consider whether there are any significant portions of the Oregon chub's range where the species is in danger of extinction or likely to become so within the foreseeable future.

The Act does not define the term “foreseeable future.” For the purpose of this rule, we define the “foreseeable future” to be the extent to which, given the amount and substance of available data, we can anticipate events or effects, or reliably extrapolate threat trends, such that we reasonably believe that reliable predictions can be made concerning the future as it relates to the status of the Oregon chub. In considering the foreseeable future as it relates to the status of the Oregon chub, we considered the factors affecting the Oregon chub, historical abundance trends, and ongoing conservation efforts.

The following analysis examines all five factors currently affecting, or that are likely to affect, the Oregon chub within the foreseeable future.

A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range

When the Oregon chub was listed as endangered in 1993, the species was known to exist at nine locations, representing only 2 percent of the species' historical range (Markle 1991, pp. 288-289; Scheerer
et al.
2007, p. 2; 58 FR 53800, October 18, 1993, p. 53800). The decline in Oregon chub abundance and distribution was attributed to the extensive channelization, dam construction, and chemical contamination that occurred in the Willamette River Basin, particularly from the 1940s through the late 20th century (Pearsons 1989, pp. 29-30).

Since listing, concerted efforts by Federal, State, and local governments and private landowners have greatly reduced the threats to the Oregon chub. For example, the introduction of the Oregon chub into secure habitats has created refugial populations in habitats that are isolated from the threats of habitat loss and invasion by nonnative fishes. Additionally, as explained below, research has expanded our understanding of suitable habitat for the Oregon chub, and increased survey efforts have led to the discovery of many natural populations. Since 2002, the USACE has implemented minimum dam outflow targets that sustain downstream floodplain habitat, which has reduced the threat of habitat loss for the Oregon chub. These minimum flow targets will continue to be required into the future under existing biological opinions from the Service and NMFS on the USACE's Willamette River Basin Project (see description below). The USACE also has a MOU with TNC regarding the Sustainable Rivers Project, an ongoing collaboration to promote ecologically sustainable flows below USACE dams in the Willamette River Basin. For these reasons, we anticipate that the USACE will continue to meet these minimum flow targets after delisting of the Oregon chub. Also, the acquisition of floodplain habitat for long-term conservation and restoration, including off-channel locations preferred by the Oregon chub, has gained momentum in the Willamette River Basin by a variety of Federal, State, Tribal, local governmental and nongovernmental agencies, which provides assurances that Oregon chub habitat will continue to be managed for the species.

Since 1992, the Oregon chub was introduced and established in 21 secure, isolated habitats (Bangs
et al.
2013, p. 15). These populations contribute to recovery by providing redundancy to the naturally occurring populations, increasing the abundance of the Oregon chub in each recovery area, and providing refugial habitat that is less vulnerable, as compared to connected habitats, to the threats of habitat loss and invasion by nonnative fishes. The majority of Oregon chub individuals occur in populations at these introduction sites. In 2013, we estimated 106,408 Oregon chub in the 21 introduced populations. By contrast, we estimated 53,255 Oregon chub in the 56 naturally occurring populations. Eleven of the introduction sites are in public ownership by Federal and State agencies that manage these sites for conservation of the Oregon chub, and we have no information that suggest these sites would be managed otherwise into the foreseeable future.

The remaining 10 introduction sites are privately owned. Many of these introduction sites were created or restored under the Service's Partners for Fish and Wildlife Program managed by the staff of the Willamette Valley National Wildlife Refuge Complex. Most of these landowners have either signed conservation agreements or are participating in our Safe Harbor Program. In the interest of conserving the Oregon chub, our Safe Harbor Program participants volunteered to allow the introduction of the Oregon chub into ponds on their land, and signed management plans called cooperative agreements, which are designed to protect the species and its habitat. In exchange, the landowners received an incidental take permit that extended an exemption from take prohibitions under section 9 of the Act. If the Oregon chub is delisted, the species will no longer be protected under these take prohibitions and the incidental take permit associated with the safe harbor agreements will no longer be in effect. This means that landowners will no longer be legally bound to protect the species on their property. However, we anticipate, based on their past interest and cooperation in protecting the species, that most or all of these landowners will continue to manage their land for conservation of the Oregon chub into the future as described in their cooperative agreements. We will also seek to extend these agreements beyond their initial 10-year time period and, in the event the property is later sold or transferred, we will work with the future landowners to enroll them in a cooperative agreement.

In 2013, 20 of the 23 populations that met the recovery plan criteria for delisting were located on State, Federal, Tribal, or other property managed for long-term conservation; 3 populations were located on privately owned property. The close knit working relationship with private landowners is extremely important for the recovery of

Oregon chub; 40 percent of all Oregon chub populations exist on privately owned property. We see no reason why the conservation efforts of landowners would cease after delisting, as all efforts have been voluntary. There are an additional 9 recently discovered or introduced populations that exist on public lands with abundances greater than 500 adult Oregon chub, further supporting our determination to delist the species.

In the 2008 5-year review of the status of the Oregon chub (Service 2008a, p. 26), we identified concerns about the ability to achieve recovery due to the focus on managing primarily isolated populations with limited genetic exchange. To reduce threats associated with habitat isolation, we suggested that future recovery efforts should integrate habitat that is connected to the floodplain. Successful efforts to integrate floodplain habitat into Oregon chub recovery were facilitated in part through consultation with several Federal agencies under section 7 of the Act. Specifically, in 2008, the Service and the NMFS completed consultation with the USACE, BPA, and the Bureau of Reclamation under section 7 of the Act on the continued operation and maintenance of 13 large flood-control dams in the Willamette River Basin, collectively known as the Willamette River Basin Project (Willamette Project). The Service's biological opinion considered the Willamette Project's effects to the Oregon chub, the bull trout, and bull trout critical habitat (Service 2008b, entire), while the NMFS' biological opinion considered effects to threatened salmon and steelhead (salmonids) and associated critical habitat (NMFS 2008, entire). The terms and conditions of the Service's biological opinion required the USACE to fund a floodplain study that would increase our understanding of the effects of flow management on connected downstream Oregon chub habitat. The ODFW subsequently pursued opportunities to study these effects and to integrate floodplain habitat in recovery efforts, in part, through funding provided by the USACE under the terms and conditions of the biological opinion.

The floodplain study required by the Willamette Project biological opinion began in 2009 (Bangs
et al.
2010a, p. 1). Under this study, the ODFW sampled fish assemblages and monitored habitat conditions (
i.e.,
bathymetry, pond volume, percent vegetation, water temperature) in several off-channel habitats in the Middle Fork Willamette River downstream of Dexter Dam in Lowell, Oregon, to Jasper, Oregon (Bangs
et al.
2010a, pp. 2-4). The ODFW chose the Dexter to Jasper reach of the Middle Fork Willamette River as a study area because several off-channel habitats in this reach were known to be occupied by the Oregon chub, and the majority of the adjacent land is in public ownership and accessible.

The ODFW sampled most of the hydrologically connected, off-channel habitat in this reach and discovered that the Oregon chub also occupied sites previously thought to be unsuitable. These sites contain greater habitat complexity than sites where Oregon chub were previously known to occur. Although these habitats have features such as beaver dams and shallow, inundated benches that were known to provide suitable habitat for Oregon chub, the recently discovered sites also include channels that have frequent connectivity to the adjacent river channel (Bangs 2013, pers. comm.). Frequently connected sites such as these were thought to be unsuitable because these sites were accessible to nonnative fishes that prey upon or compete with the Oregon chub for resources.

The discovery of Oregon chub in these connected sites facilitated a better understanding of the diversity of habitats occupied by Oregon chub, and prompted the ODFW to shift their basin-wide sampling efforts from primarily focusing on isolated habitats or habitats with infrequent river connection to sampling frequently connected, off-channel habitats. They sampled similar habitat in other recovery subbasins and found that Oregon chub also occupied many of these frequently connected habitats. Between 2009 and 2013, the ODFW discovered 34 additional Oregon chub populations throughout the 3 recovery subbasins (Bangs
et al.
2013, pp. 6-8). In 2013, 14 of the 23 populations that met the delisting criteria were in naturally occurring sloughs, beaver pools, and pond habitats. Fifty-six of the 77 habitats containing Oregon chub were naturally occurring; 21 populations were introduced. In addition, 50 Oregon chub populations are located in habitat that experiences some level of connectivity to the adjacent river channel. The Service has determined that the minimum aquatic area necessary to support a population of at least 500 adult Oregon chub is 500 square meters (m
2
) (5,400 square feet (ft
2
)) (74 FR 10412, March 10, 2009, p. 10417). Out of the 77 populations, only a single location, Dougren Island Slough, has an aquatic area smaller than 500 m
2
(5,400 ft
2
); the site is 400 m
2
(4,300 ft
2
) and supported 1,700 adult Oregon chub in 2013.

Several anthropogenic and natural environmental factors, discussed below, may continue to have effects on Oregon chub and its habitat in the foreseeable future. Many of these factors are included in this discussion because the Service previously identified them as threats to the continued existence of the species in the listing and downlisting rules. Additionally, new factors affecting the species are discussed.

Activities Related to the Willamette Project

The Oregon chub occupies 45 connected habitats that are downstream of Willamette Project dams or adjacent to reservoirs; these habitats are influenced by Willamette Project operations. The Willamette Project biological opinions were signed in 2008, and continue until 2023 (NMFS 2008, p. 1-11; Service 2008b, p. 85). In addition to normal operations of the Willamette Project, several actions required under the terms and conditions of the biological opinions may affect Oregon chub populations and habitat in the future.

Temperature and flow augmentation—
The USACE is implementing a number of structural and operational changes to alter flows and water temperatures downstream of Willamette Project dams to increase survival of federally listed salmon and steelhead (salmonids). These operational and structural changes have resulted in downstream water temperatures closer to that which existed prior to the construction of the dams (
i.e.,
river temperatures downstream of the reservoirs are now warmer in early summer, and cooler in the late summer and early fall). The USACE also operates to meet mainstem and tributary flow objectives identified in the Willamette Project biological opinion to benefit listed salmonids; these flows also benefit the Oregon chub by sustaining floodplain habitat downstream. In addition, the USACE works with partners in the Willamette River Basin as part of TNC's Sustainable Rivers Project to implement a set of environmental flow objectives designed to improve channel morphology in a manner that will create and sustain new, and improve existing, fish habitat (Gregory
et al.
2007, p. 11).

The effects of water flow augmentation and temperature normalization on fish communities in off-channel habitat are largely unknown. The ODFW has a monitoring program in place (Bangs
et al.
2011a, entire) to detect any negative effects on Oregon chub and its habitat. With the delisting of Oregon chub, this monitoring

program, which is detailed in our PDM plan, will continue for several years post-delisting (Service and ODFW 2013, entire). The PDM plan identifies thresholds and responses for detecting and reacting to significant changes in Oregon chub protected habitat, distribution, and persistence. If declines are detected that exceed the thresholds, the Service, in combination with other PDM participants, will investigate causes of these declines and determine if the Oregon chub warrants expanded monitoring, additional research, additional habitat protection, or relisting as an endangered or threatened species under the Act. Additional discussion about temperature and instream flows is presented in the “Effects of Climate Change” section (also in Factor A).

Reservoir drawdowns—
As required in the NMFS biological opinion for the Willamette Project, the USACE is implementing an annual complete reservoir drawdown of Fall Creek Reservoir on the Middle Fork Willamette River. The biological objectives of the reservoir drawdown are to improve fish passage efficiency and survival of juvenile Chinook salmon migrating out of Fall Creek Reservoir, and to reduce nonnative fish populations inhabiting the Fall Creek Reservoir. This is expected to result in reduced nonnative predation and competition with juvenile Chinook salmon rearing in the reservoir. While reservoir drawdown benefits Chinook salmon, there are potential negative effects to the Oregon chub from sedimentation of Oregon chub habitats.

Willamette River Basin flood control dams inhibit the transport of sediment downstream, causing sedimentation to occur in the reservoirs. During a complete reservoir drawdown, released reservoir water scours the reservoir bed and transports sediment downstream. During the initial Fall Creek Reservoir drawdowns, a massive volume of silt, sand, and debris was flushed, causing sediment deposition to occur in off-channel habitats downstream of the dam. Sampling for Oregon chub populations in the Fall Creek drainage occurred after the first drawdown and three previously undocumented Oregon chub populations were found. The extent to which these populations were affected is unknown because Oregon chub were discovered at these sites after the sedimentation occurred and we cannot determine the area of habitat or number of Oregon chub that existed prior to the sedimentation. Fewer than five Oregon chub were found in each of these three sites after the sedimentation occurred. These sites experienced the accumulation of fine sediments, perhaps beyond typical historical levels, which reduced the amount of habitat available to Oregon chub (Bangs 2013, pers. comm.). However, little sedimentation was observed in the few Oregon chub habitats that occur farther downstream of the confluence of Fall Creek and the Middle Fork Willamette River. Most of the abundant populations of Oregon chub in off-channel habitats of the Middle Fork Willamette River were not affected because they occur upstream of these impacts.

Although partial drawdowns of Willamette Project reservoirs are likely to occur in the near future, they are unlikely to result in large volumes of sediment moving downstream because the water level will remain above the sediment bed and little sediment will be moved. Complete reservoir drawdowns to the extent seen at Fall Creek are not currently planned at other reservoirs. The effects of a complete reservoir drawdown would vary by location; it is difficult to predict what habitat changes may occur downstream. However, any future proposal to implement this scale of drawdown will include extensive coordination and planning among the Service, ODFW, USACE, and other land managers. Additionally, in cooperation with the USACE, we developed monitoring guidance and recommended responses in the event a drawdown is planned (Service and ODFW 2013, pp. 18-19). We do not anticipate that potential negative impacts from reservoir drawdowns will affect the overall status of Oregon chub. Additional discussion about reservoir drawdown is presented in the “Effects of Climate Change” section (also in Factor A).

Another concern related to drawdowns is that nonnative predatory fishes are common in reservoir habitats. During a drawdown, these fish are likely transported downstream, where they may invade off-channel habitats. The risks to the Oregon chub associated with nonnative fishes are discussed under Factors C and E, below.

Reservoir water level fluctuations—
Fluctuating water levels in Lookout Point Reservoir on the Middle Fork Willamette River may limit the breeding success of the Oregon chub population in Hospital Pond, which provides habitat for the species in a pool connected to the reservoir by a culvert (Service 2008b, p. 160). Between 2001 and 2003, the USACE, which manages Lookout Point Reservoir as part of the Willamette Project, implemented a series of actions to protect the population of Oregon chub in Hospital Pond. The goal was to allow the USACE to manage the water level in Lookout Point Reservoir independently of the water elevation in Hospital Pond. In order to achieve this, they installed a gate on Hospital Pond's outlet culvert and lined the porous berm between the pond and reservoir (Service 2002, pp. 1-11). They also excavated additional areas to create more suitable spawning habitat in the pond (Service 2003, pp. 1-3).

Despite these actions, water elevation in Hospital Pond continues to be influenced by reservoir water levels. Hospital Pond currently supports a large, stable population of the Oregon chub; however, future Willamette Project operations may result in reservoir elevations that are below the levels necessary to inundate the spawning habitat in Hospital Pond (Service 2008b, p. 160). This reduction in spawning habitat may result in limited breeding success for the Oregon chub in Hospital Pond into the foreseeable future. However, the Hospital Pond population is not critical to meeting recovery criteria because additional surveys in the Middle Fork Willamette River subbasin have found that the subbasin has the highest number of Oregon chub populations (29 populations) across the range of the species. Currently, 17 of the Oregon chub sites in this subbasin have abundant (greater than 500 individuals) populations of the Oregon chub. This redundancy of large populations provides additional security to the species in the event that single populations decline.

Inability to meet minimum flow targets—
During low water or drought years, the USACE may not be able to meet the seasonal minimum water flow targets established in the Willamette Project biological opinions. Analysis performed by the USACE determined that from 1936 to 1999, low flow and drought conditions occurred 9 percent and 16 percent of the years, respectively (USACE 2007, pp. 2-45). If this occurs in the future, it may have negative effects on Oregon chub habitat downstream through a temporary reduction in pond volume and increased water temperatures. Under the floodplain study, the ODFW mapped the bathymetry (habitat depth) and installed equipment to measure pond elevation, area, volume, and temperature in Oregon chub sites that are influenced by Willamette Project flows. This information was used to determine the effect that low flows may have on the extent of habitat area available to Oregon chub. The USACE has considered these data in managing flows and has a notification process in

place to coordinate with the Service and the ODFW during low water periods before flows are reduced to levels below the minimum flow targets. To date, except for during malfunctions and emergency operations explained below, flows below minimum targets have been of short duration and have not resulted in observable adverse effects to Oregon chub populations (Bangs 2013, pers. comm.). Further, when minimum targets cannot be met, the Service, ODFW, NMFS, and USACE coordinate on a regular basis to discuss reduced flow releases in advance; this coordination allows the Service to weigh in on the magnitude of reductions and mitigate any reductions in flows that may affect Oregon chub populations. This coordination will continue into the future, as required by the two biological opinions, for other listed fish species (Service 2008b, pp. 38-40; NMFS 2008, pp. 2-39 to 2-43).

Willamette Project malfunctions and emergency operations resulting in the USACE not meeting minimum flow targets or necessitating restrictions on reservoir pool elevations have affected Oregon chub habitats. These incidents have been infrequent, but resulted in short-term negative effects on a few Oregon chub populations. For instance, in 2009, two of the three spillway gates at the USACE Big Cliff dam on the North Santiam River failed (Bangs
et al.
2010b, p. 16). While repairing the gates, the outflow from Big Cliff Dam was reduced to below the minimum summer flow target. Record high air temperatures coincided with the low flow levels. Monitoring during this event detected that three Oregon chub sites downstream were nearly desiccated and fish mortalities were observed. Screened pumps were used to increase the volume of water in the ponds and to reduce water temperatures. The effects of this incident on Oregon chub populations were short-term, and the numbers of Oregon chub in these three populations have either increased or are exhibiting a stable trend (Bangs
et al.
2013, pp. 6-8).

The minimum flow targets protect not only the Oregon chub, but many other native aquatic species, including listed salmonids. If the Oregon chub is delisted, these minimum flow targets will continue to be required under existing biological opinions from the Service and the NMFS on the Willamette Project for listed bull trout, Chinook salmon, and steelhead. Moreover, the USACE was proactive in implementing recommended flows before the Willamette Project biological opinions were completed (USACE 2007, pp. 3-19). Therefore, we anticipate that the USACE will continue to meet these minimum flow targets after delisting of the Oregon chub, except under infrequent, extreme conditions such as drought.

In 2010, the USACE determined that the condition and reliability of the spillway gates at 13 Willamette Project dams represented an unacceptable risk to public safety (Bangs
et al.
2011b, p. 16). To mitigate this risk, the USACE proposed implementing pool elevation restrictions at Willamette Project reservoirs to lower than normal levels to support maintenance and repair of the spillway gates. The imposed restrictions affected one population (Dexter Reservoir Alcove “PIT1” site) of Oregon chub by reducing the pond below levels critical for Oregon chub survival. The Dexter Reservoir Alcove “PIT1” site had filled with sediment over the years and in consultation with the USACE, we determined that removing some of this sediment was the best measure to prevent desiccation of the pond. Prior to removing sediment, the ODFW captured and relocated a total of 1,127 Oregon chub to Hills Creek Pond, a site with perennial flow located on USACE property at Hills Creek Dam. This site is within the historical range of Oregon chub, but at the time was not occupied by the species. The pond site is adjacent to the Middle Fork Willamette River and has historically been managed by USACE staff for wildlife habitat enhancement. The spillway gate repairs were completed, the pool elevation restriction for Dexter Reservoir was lifted in 2011, and the reservoir has returned to normal operations. The Oregon chub population abundance in Dexter Reservoir Alcove “PIT1” site and Dexter RV Park Pond “DEX3” are both currently stable and contribute towards meeting recovery criteria for delisting (Bangs
et al.
2013, p. 8). The translocation of Oregon chub into Hills Creek Pond created a large, secure population that is now the largest Oregon chub population within the Middle Fork Willamette River subbasin with an estimated abundance of 14,610 Oregon chub (Bangs
et al.
2013, p. 8). Additional discussion about minimum flow requirements is presented in the “Effects of Climate Change” section (also in Factor A).

Siltation Resulting From Timber Harvest

As previously noted, Oregon chub habitats are generally associated with low gradient floodplain habitats not generally subject to timber harvest activities. However, there are a small number of Oregon chub populations that exist within, or adjacent to, forested landscapes that were, or could be, subject to adverse effects of timber harvest. These adverse effects include siltation (deposition of fine sediment) of stream habitats from ground-disturbing activities involved with standard logging practices. State and private lands in Oregon are subject to water quality as well as fish and wildlife protective measures under the Oregon Forest Practices Act, whereas Federal lands are subject to land and resource management plans that also provide protective guidelines for water quality and fish and wildlife protections. While siltation resulting from timber harvest has not been identified as a significant threat to Oregon chub, there is at least one instance where siltation from timber harvest may have contributed to a decrease in habitat suitability and availability that resulted in a drop in chub abundance.

In the 1990s, timber harvest occurred on private lands upstream of East Fork Minnow Creek. Flood events in the watershed in 1996, 1997, and 1998 caused accelerated siltation into East Fork Minnow Creek Pond, a pond downstream that is occupied by Oregon chub, and over half of the habitat was lost (Scheerer 2009, pers. comm.). The Oregon chub population in East Fork Minnow Creek Pond declined dramatically following these events (Scheerer 2009, pers. comm.). In 2010, the Oregon Department of Transportation excavated accumulated sediment in the pond and created a pool that will provide a buffer from the effects of future siltation. The population subsequently rebounded and it now meets the delisting criterion for a stable or increasing trend over 7 years.

In 2012, timber harvest on private land occurred upstream of an Oregon chub site on the William L. Finley National Wildlife Refuge (Finley NWR) known as Gray Creek Swamp. Due to concerns about potential sedimentation to Oregon chub habitat in Gray Creek Swamp, we negotiated with the landowner who agreed to increase the width of the no-cut riparian buffer along the streams within the harvest area to reduce the risk of siltation in Oregon chub habitat downstream. Siltation of this Oregon chub habitat following harvest has not been observed, but the site will continue to be monitored by the ODFW during the 9-year post-delisting monitoring period.

The potential for adverse effects to Oregon chub habitat from timber harvest was also identified at three other sites: Dexter Reservoir Alcove “PIT1” site, Buckhead Creek, and Wicopee Pond (Scheerer 2008, pers. comm.). However, we did not observe levels of siltation at

these sites that resulted in habitat loss, and all of the Oregon chub populations within each of the five sites located downstream of harvest activities met the delisting criteria in 2013. Additionally, the U.S. Forest Service (USFS) manages several Oregon chub sites within the Willamette National Forest. As noted above, forests managed by the USFS operate under land and resource management plans that include management practices protective of fish (USFS 1990, pp. IV-61-64), and we anticipate these resource management plans will continue to guide forest management into the future.

While future siltation of habitats occupied by Oregon chub from timber harvest activities clearly is possible, the frequency is anticipated to be very low, as will be the potential number of affected populations. Given this fact, and the protections afforded by the Oregon Forest Practices Act and Federal land management plans, we do not believe siltation from timber harvest represents a substantial population-level threat to Oregon chub now or in the foreseeable future.

Floods and Seasonal High-Water Events

The Oregon chub is a low-elevation, floodplain-dependent species that evolved under dynamic environmental conditions created by seasonal flooding and droughts. As a result, the species' life history reflects these dynamic conditions. While floods and seasonal high-water events constitute a potential stressor to individuals or specific Oregon chub populations, these events create and maintain off-channel habitats necessary for the long-term persistence of the species, and they function to transport the Oregon chub to colonize these new sites.

For example, in 2007, a flood event in the Santiam River caused channel avulsion (a shift in the stream channel that results in the rapid abandonment of a river channel and formation of a new river channel) at an Oregon chub site, reducing the extent of habitat available at this location and likely negatively affecting this population. Yet in another example, between 2000 and 2003, new off-channel habitat formed in the McKenzie River due to flooding and, after aquatic vegetation became established, the site was subsequently colonized by the Oregon chub (Bangs 2013, pers. comm.). Although we cannot predict the magnitude or the extent to which current Oregon chub habitats may be affected by flooding and seasonal high water events, the number and distribution of large populations, in combination with habitat heterogeneity, increases the species' resilience in recovering from periodic disturbance, as the species would have historically. Additional discussion about increased flood events is presented in the “Effects of Climate Change” section (also in Factor A).

Water Quality Issues

The analysis of threats in the final rule to list the Oregon chub as an endangered species and the recovery plan for the species discussed numerous potential threats to water quality in Oregon chub habitats. However, in the 20 years since the Oregon chub was listed, only a few of these concerns, discussed below, have materialized, and even then, these were localized and of short duration.

In the spring of 2011, the ODFW noted the complete die-off of the introduced Oregon chub population in Cheadle Pond on the Finley NWR. They assessed the water quality (temperature, pH, and dissolved oxygen) and discovered that the pH level was abnormally high (mean pH: 9.6, range: 8.4-10.2). The pH level in Oregon chub habitats typically ranges between 7.42 and 8.66. The cause of the increased pH level was unknown and had not been observed previously at this site. The ODFW subsequently conducted an in-situ 7-day bioassay using 30 adult Oregon chub from the Gray Creek Swamp population. All of the Oregon chub survived the trial and were released into Cheadle Pond following the bioassay. We have not observed, and do not anticipate based on this one event, similar incidents in other Oregon chub habitats.

Nutrient enrichment may have caused the extirpation of the Oregon chub population at Oakridge Slough in the Middle Fork Willamette River subbasin. The slough is downstream from the Oakridge Sewage Treatment Plant, and increased nitrogen and phosphorus concentrations were detected in the slough prior to a decline in the population. While the nutrient concentrations are not believed to be directly harmful to the species, the elevated nutrient levels may have contributed to habitat conditions that were unsuitable for Oregon chub (
i.e.,
an increase in growth of algae, which then decomposed and led to low oxygen conditions below what the Oregon chub requires to survive) (Buck 2003, p. 12).

Several Oregon chub sites are located adjacent to agricultural land. Runoff from farm fields may contain pesticides or fertilizers that could adversely affect the water quality in Oregon chub habitats. However, many of these sites have protective vegetated buffers between crops and the aquatic habitat. To date, we have not observed declines in Oregon chub populations that can be attributed to agricultural practices, and several Oregon chub habitats located adjacent to farmland have supported abundant populations of Oregon chub for many years.

Several Oregon chub sites are located adjacent to private forestland (as previously discussed above under “Siltation Resulting from Timber Harvest”). Additionally, the USFS manages several Oregon chub sites within the Willamette National Forest. Forests managed by the USFS operate under land and resource management plans that include management practices protective of fish (USFS 1990, pp. IV-61-64), and we anticipate these resource management plans will continue to guide forest management into the foreseeable future. On private forestland, the use of chemicals is regulated by the Oregon Department of Forestry, and operators are required to comply with product labels and additional protective measures to protect waters of the State, including leaving untreated vegetated buffers and limiting aerial applications near areas of standing open water larger than one-quarter acre (Oregon Revised Statutes (ORS) 527.765 and OAR 629-620-0000 through 629-620-0800). Although we have no information regarding landowners' compliance with these rules on forestland in the vicinity of Oregon chub habitats, we have not observed harmful effects to Oregon chub populations due to chemical exposure related to forestry operations.

During our analysis of the factors affecting the Oregon chub, we determined that spills via sewage discharge, hazardous cargo from trucks, railways and pipelines, which were identified as threats when the species was first listed, no longer pose a significant threat to the species. At the time of listing, of the nine Oregon chub populations known to exist, seven of these locations were directly adjacent to major transportation corridors where threats to water quality had the potential to impact Oregon chub. Currently, Oregon chub have been documented in 77 populations widely distributed throughout the Willamette River Basin; 20 of these locations are adjacent to transportation corridors. In addition, two populations are adjacent to sewage treatment plants. Despite the proximity to potential threats to water quality, in the 20 years since the Oregon chub was listed, only a few of these concerns have materialized, and even then, these were localized and of short duration. The current distribution of the Oregon chub in many abundant

populations located across multiple subbasins reduces the risk that the above factors will affect a large portion of Oregon chub and its habitat. In summary, we conclude that none of the existing or potential water quality-related threats, either alone or in combination with others, constitutes a substantial threat to the Oregon chub now or in the foreseeable future. Additional discussion about temperature and dissolved oxygen levels is presented in the “Effects of Climate Change” section (also in Factor A).

Aggradation

Aggradation is an alluvial process where sediment deposition (deposition of all sizes of sediments, both coarse and fine) is more rapid than the capacity of a river to transport sediment downstream. We observed aggradation at the Geren Island North Channel in the North Santiam River. Natural movement of the river channel changed sediment deposition in the upstream end of this location, which had the potential to block water flow into the site. The City of Salem, which manages the site, excavated a portion of the channel to allow free-flowing water to enter Oregon chub habitat. To date, we have not observed a decline in the Geren Island population. With the exception of this site and habitats in Fall Creek, which we discussed previously, no other Oregon chub habitats are negatively impacted by aggradation. We consider the potential negative impacts to the overall status of Oregon chub from aggradation to be very low now and in the foreseeable future.

Succession

Succession resulting from the manipulation of river flows was identified as a potential threat to Oregon chub habitat in the downlisting rule (75 FR 21179, April 23, 2010). Succession is a natural, long-term ecological process that ponds go through as they mature. As vegetation dies back seasonally, it deposits on the substrate of the pond, causing a reduction in water depth over time. Eventually, plant communities shift from aquatic to amphibious wetland plants, and the open-water ponds are replaced by seasonal wetland and marsh habitat. Historically, seasonal high flows and alluvial floodplain processes created off-channel habitat, and rejuvenated existing habitats by flushing out sediment and diversifying the aquatic plant community. These processes no longer function as they did historically because flows are regulated under the USACE's Willamette Project. The Willamette Project dams were constructed in the 1940s through the 1960s. Oregon chub populations have persisted under managed flow conditions for more than 60 years. In addition, under the Service's Willamette Project biological opinion (Service 2008b, pp. 40-51) and the NMFS Willamette Project biological opinion (NMFS 2008, pp. 2-43 to 2-52), minimum flow levels established for listed salmonids will continue to protect Oregon chub habitat. Other non-regulatory efforts are working to restore floodplain function and sediment transport, such as TNC's Willamette Sustainable Rivers Project. In this project, TNC has developed an MOU with the USACE to release stored water in high-flow pulses to restore natural processes in managed portions of the Middle Fork, McKenzie, and Santiam Rivers. Given the MOU between the USACE and TNC regarding the Sustainable Rivers Project, and the minimum flows required under existing biological opinions from the Service and NMFS, we anticipate flow management trending towards natural flow regimes below Willamette Project dams will continue to create and rejuvenate off-channel habitats and benefit Oregon chub into the future.

We are not aware of any particular sites that are vulnerable to succession in the near future; however, the sites that remain hydrologically isolated during high flows are cut off from these natural processes, and succession may continue resulting in a reduction of open water habitat. For instance, succession occurred at Herman Pond, an isolated Oregon chub site in the Coast Fork Willamette Basin, which led to a reduction in habitat area and a decline in population abundance. In 2005, the site was excavated to remove successional vegetation. This activity was successful in increasing open water habitat and led to an increase in Oregon chub abundance at this location. Given the wide distribution and number of Oregon chub habitats under different land ownership, we are uncertain whether manual modification of chub habitats to reverse the effects of succession will occur in the future following delisting. However, given that we are not aware of any particular sites vulnerable to succession in the foreseeable future, we determined that there is very little potential negative impact, if any, to the overall status of Oregon chub from succession.

Irrigation Withdrawals

A few Oregon chub sites may be influenced by irrigation water withdrawals. In recent years, at Elijah Bristow Berry Slough in the Middle Fork Willamette River subbasin, a drop in summer water level and a significant decline in Oregon chub abundance coincided with increased irrigation use by a farm located upstream. However, this was an isolated event that we have not observed at other sites. Many Oregon chub populations occur on publicly owned lands or on areas managed for conservation, where direct water withdrawals do not occur. In addition, water levels at habitats adjacent to mainstem river channels are highly dependent on river flow, and are less likely to be negatively impacted by irrigation withdrawals due to the amount of hyporheic (subsurface) flow into these habitats from the adjacent river. Based on the wide distribution of Oregon chub, we consider the potential negative impact to the overall status of Oregon chub from irrigation withdrawals to be very low.

Effects Related to Climate Change

Our analyses under the Act include consideration of observed or likely environmental changes resulting from ongoing and projected changes in climate. As defined by the Intergovernmental Panel on Climate Change (IPCC), the term “climate” refers to the mean and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (IPCC 2013a, p. 1450). The term “climate change” thus refers to a change in the mean or the variability of relevant properties, which persists for an extended period, typically decades or longer, due to natural conditions (
e.g.,
solar cycles) or human-caused changes in the composition of atmosphere or in land use (IPCC 2013a, p. 1,450).

Scientific measurements spanning several decades demonstrate that changes in climate are occurring. In particular, warming of the climate system is unequivocal, and many of the observed changes in the last 60 years are unprecedented over decades to millennia (IPCC 2013b, p. 4). The current rate of climate change may be as fast as any extended warming period over the past 65 million years and is projected to accelerate in the next 30 to 80 years (National Research Council 2013, p. 5). Thus, rapid climate change is adding to other sources of extinction pressures, such as land use and invasive species, which will likely place extinction rates in this era among just a handful of the severe biodiversity crises observed in Earth's geological record (American Association for the Advancement of Sciences (AAAS) 2014, p. 17).

Examples of various other observed and projected changes in climate and associated effects and risks, and the basis for them, are provided for global and regional scales in recent reports issued by the IPCC (2013c, 2014), and similar types of information for the United States and regions within it can be found in the National Climate Assessment (Melillo et al. 2014, entire).

Results of scientific analyses presented by the IPCC show that most of the observed increase in global average temperature since the mid-20th century cannot be explained by natural variability in climate and is “extremely likely” (defined by the IPCC as 95 to 100 percent likelihood) due to the observed increase in greenhouse gas (GHG) concentrations in the atmosphere as a result of human activities, particularly carbon dioxide emissions from fossil fuel use (IPCC 2013b, p. 17 and related citations).

Scientists use a variety of climate models, which include consideration of natural processes and variability, as well as various scenarios of potential levels and timing of GHG emissions, to evaluate the causes of changes already observed and to project future changes in temperature and other climate conditions. Model results yield very similar projections of average global warming until about 2030, and thereafter the magnitude and rate of warming vary through the end of the century depending on the assumptions about population levels, emissions of GHGs, and other factors that influence climate change. Thus, absent extremely rapid stabilization of GHGs at a global level, there is strong scientific support for projections that warming will continue through the 21st century, and that the magnitude and rate of change will be influenced substantially by human actions regarding GHG emissions (IPCC 2013b, 2014; entire).

Global climate projections are informative, and, in some cases, the only or the best scientific information available for us to use. However, projected changes in climate and related impacts can vary substantially across and within different regions of the world (
e.g.,
IPCC 2013c, 2014; entire) and within the United States (Melillo et al. 2014, entire). Therefore, we use “downscaled” projections when they are available and have been developed through appropriate scientific procedures, because such projections provide higher resolution information that is more relevant to spatial scales used for analyses of a given species (see Glick et al. 2011, pp. 58-61, for a discussion of downscaling).

Various changes in climate may have direct or indirect effects on species. These may be positive, neutral, or negative, and they may change over time, depending on the species and other relevant considerations, such as interactions of climate with other variables such as habitat fragmentation (for examples, see Franco et al. 2006; Forister et al. 2010; Galbraith et al. 2010; Chen et al. 2011). In addition to considering individual species, scientists are evaluating potential climate change-related impacts to, and responses of, ecological systems, habitat conditions, and groups of species (
e.g.,
Deutsch et al. 2008; Berg et al. 2010; Euskirchen et al. 2009; McKechnie and Wolf 2010; Sinervo et al. 2010; Beaumont et al. 2011; McKelvey et al. 2011; Rogers and Schindler 2011).

Climate change effects present substantial uncertainty regarding the future environmental conditions in the Willamette River Basin and may place an added stress on the Oregon chub and its habitats. The IPCC has concluded that recent warming is already strongly affecting aquatic biological systems, as evidenced by increased runoff and earlier spring peak discharge in many glacier- and snow-fed rivers (IPCC 2007, p. 8). Projections for climate change effects in North America include decreased snowpack, more winter flooding, and reduced summer flows (IPCC 2007, p. 14), which may increase periods of drought (Oregon Climate Change Research Institute (OCCRI) 2010a, p. 112).

Observed changes in temperature in the Pacific Northwest (PNW) already show an increase of 1.5 degrees Celsius over the past century due to human activities (OCCRI 2010b, p. 6). Global climate models project temperature increases for the PNW of approximately 2 to 4 degrees Celsius (3 to 10 degrees Fahrenheit) by 2080 (OCCRI 2010b, p. 7). Projections for climate change effects in the Willamette Valley in the next century also include warmer air temperatures that will lead to lower soil moisture and increased evaporation from streams and lakes (Climate Leadership Initiative (CLI) and National Center for Conservation Science and Policy (NCCSP) 2009, p. 9; OCCRI 2010a, p. 71). The frequency of short-term (3- and 6-month) droughts in the Willamette Valley will likely increase due to decreased summer rainfall, which may result in reduced summer baseflows and exacerbate water temperature increases. However, long-term droughts (12 and 24 months) are not projected to substantially change across most of the Willamette Basin (OCCRI 2010a, p. 112).

The 29,700-km
2
(11,467-mi
2
) Willamette River Basin is a large complex river basin, influenced by two mountain ranges: the Cascades and the Coast Range (Chang and Jung 2010, pp. 187-190). The rain-dominated Coast Range occupies about 20 percent of the basin; the Cascade Range occupies more than 50 percent, and includes the rain-dominated Western Cascades and the snow-dominated High Cascades. The Willamette Valley region lies between these two ranges. Thus, the basin has complex terrain and geology, and a wide range of elevations that influence the timing and magnitude of runoff. Given this physical variability, the effects of climate change will not uniformly affect all areas or subbasins of the Willamette River (Chang and Jung 2010, pp. 194-204).

The hydrology of the Willamette River Basin is largely influenced by winter rainfall and spring snowmelt, with 77 percent of the flow occurring between November and April (Chang and Jung 2010, p. 190). Overall, the Willamette Basin is considered water abundant in Oregon. In addition to rainfall, the basin is influenced by spring snowmelt and spring-fed tributaries at higher elevations (
e.g.,
High Cascades region), and shallow groundwater aquifers in low-elevation areas in the valley that recharge during the rainy season (OCCRI 2010a, p. 97-104). The Willamette River and its tributaries are highly altered with multiple large reservoirs and other human influences such as dams, levees, and floodplain development. Multiple, large USACE dams, constructed in the 1950s and 1960s for flood reduction, altered seasonal discharge and temperatures, reduced peak flood flows, and augmented summer low flows (OCCRI 2010a, p. 77). Climate change effects that may affect Oregon chub include increased winter flooding, increased temperatures, reduced summer baseflows, and increased negative interactions with nonnative fishes. Each of these is discussed below.

Increased Winter Floods—
Effects of climate change predicted for the PNW may include increased winter flood events (OCCRI 2010a, pp. 87-88). These events, which are often associated with an increased proportion of annual precipitation falling as rain instead of snow and reduced snowpack, may better mimic natural riverine processes (such as channel migration, scour, etc.) to create and maintain riverine habitats on which Oregon chub depend. Oregon chub evolved in a dynamic, alluvial river with broad floodplains and braided reaches with many side channels, sloughs, and other similar slack-water habitats. Large floods

commonly rearranged these side-channel habitats, creating new habitats in some locations, and filling in other areas. The construction and operation of the USACE's Willamette Project, a system of 13 flood control dams, has reduced flooding and associated habitat forming processes in the Willamette River Basin, thereby simplifying mid- to low-elevation, aquatic habitats considerably. During previous flood events, the Willamette Project dams have been able to capture and reduce the magnitude of the flow to keep flood waters from impacting downstream communities; the magnitude of these flows were still high enough to alter the stream and floodplain habitat. Increased flows associated with climate change may contribute to the creation and maintenance of off-channel floodplain habitats upon which Oregon chub depend (
e.g.,
side channels, oxbows, etc.), thereby increasing the amount of suitable habitat for the species. For these reasons, it is possible that increases in winter floods associated with climate change may benefit Oregon chub through the creation and maintenance of their habitats.

Temperature and Dissolved Oxygen Effects—
The Oregon chub is tolerant of a wide range of temperatures and thus less vulnerable to temperature effects of climate change than other listed fish species in the Willamette River Basin (
e.g.,
bull trout, spring chinook salmon, and winter steelhead). Oregon chub do not require cool temperatures for spawning or other life-history needs and appear tolerant of low dissolved oxygen (DO) levels. DO levels and temperature are related because at higher temperatures, water has a reduced ability to store oxygen. While the upper lethal temperature limit of Oregon chub has not been determined, the best available data based on field observations suggest this limit is approximately 31 to 35 degrees Celsius (88 to 95 degrees Fahrenheit) for adult Oregon chub, and that tolerance may be associated with low DO levels (Scheerer and Apke 1997, p. 25; Bangs et al. 2009, p. 17). Temperature and DO tolerances for juvenile Oregon chub appear to be higher than that of adults (Scheerer and Apke 1997, p. 25; Bangs et al. 2009, p. 17). The observed maximum summer temperature range of occupied Oregon chub habitat is from 23 to 39 degrees Celsius (73 to 102 degrees Fahrenheit) (Bangs 2014, pers. comm.). Despite a proportion of these habitats experience temperatures in excess of 35 degrees Celsius (95 degrees Fahrenheit) (which may result in the loss of some individuals within that population), an entire population has not been lost due to temperature increases and associated low DO levels.

While global climate models project a temperature increase for the PNW of approximately 2 to 4 degrees Celsius (3.6 to 7.2 degrees Fahrenheit) by 2080 (OCCRI 2010b, p. 7), climate models primarily predict air temperature changes, which have led many to believe that water temperatures will also correspondingly rise (Arismendi
et al.
2012, p. 1). However, water temperatures did not follow expected warming trends or experience the same magnitude of increased temperature as air temperature when analyzing stream temperature data from the Pacific continental United States (Arismendi
et al.
2012, p. 4). In many cases, water temperatures were found to have more cooling trends than warming trends since 1987, and less variability, especially in highly human-influenced rivers (Arismendi
et al.
2012, pp. 4-5). Such is the case in the Willamette River; the presence of the 13 USACE flood control dams in the Willamette Valley allows for some amelioration of extreme climate variation, such as temperature extremes and drought. These large dams may be able to adaptively operate in the future to partially offset some of the potential increases in water temperature and flow reductions below the dams, if determined appropriate.

Releases of water below the USACE's Willamette Project dams generally target water temperatures ranging from 12 to 18 degrees Celsius (54 to 64 degrees Fahrenheit), depending on the season. These releases decrease downstream summer river temperatures by 6 to 10 degrees Celsius (10.8 to 18 degrees Fahrenheit) from historic temperatures (Rounds 2010, p. 43) and augment summer low flows (OCCRI 2010a, p. 77). The USACE is working to better mimic historical temperature conditions through water releases at several dams, which primarily target temperature benefits to federally listed salmonids that remain protected under the Act. These salmonid species require much cooler waters than Oregon chub. For example, juvenile salmonids generally prefer temperatures from 11.7 to 14.7 degrees Celsius (53.1 to 58.5 degrees Fahrenheit), and spawning temperatures for these species are typically below 13.0 degrees Celsius (55.4 degrees Fahrenheit) (Richter and Kolmes 2005, pp. 27-28). The needs of these listed salmonids will continue to influence future management decisions. Thus, dam releases targeting these cooler temperature requirements will be protective of Oregon chub habitats downstream of these dams.

Potential reductions in summer baseflows may increase water temperatures (OCCRI 2010a, p. 114). Increased frequency of short-term droughts (3 to 6 months) may reduce the USACE's ability to meet all of the minimum instream flow volumes, especially during late summer and early fall. Many populations (40 out of 77 populations, and 10 of the 23 populations that meet recovery criteria) exist in riverine habitats influenced by releases from the USACE's dams.

While increased frequency of short-term drought may reduce the USACE's ability to meet required instream flows for listed salmonids, we do not anticipate these reductions will result in temperature increases that constitute a substantial threat to Oregon chub now or into the foreseeable future. These dams currently maintain cooler summer temperatures and higher summer baseflows below the dams than existed prior to dam construction, and thereby provide a buffer from increased temperatures. Further, the USACE is required to coordinate with the Service, ODFW, and NMFS when minimum instream flows cannot be met, which allows the Service to weigh in on the magnitude of reductions and mitigate negative effects to Oregon chub populations if necessary. For these reasons, we determine potential instream flow reductions, and any associated temperature increases and reduced DO levels due to increased short-term droughts do not constitute a substantial threat to Oregon chub in habitats below the dams.

Other populations exist outside the influence of the dam releases. Eighteen populations exist in “up-slope” habitats that are not directly influenced rivers (6 of these populations met all recovery criteria in 2013); 14 populations occur on or adjacent to undammed rivers (3 met recovery criteria); 5 are adjacent to USACE reservoirs (4 met recovery criteria). The potential effects to each of these habitat categories are discussed below.

The 18 “upslope” populations were introductions into isolated ponds, as discussed above. Predicted reductions in summer rainfall and increased evaporation may reduce the volume or depth of these ponds in late summer, increase water temperature, and correspondingly decrease DO levels in these habitats. However, these introduction sites were selected because the habitat is expected to remain stable during extreme climatic events such as droughts or floods. Each of these habitats was chosen for its ability to remain wetted during drought and provide a diversity of habitats

throughout a range of pool elevations. For example, some sites rely on ground water springs or modern water control structures to maintain pond elevations throughout summer.

While it is possible that climate change may impact some aquatic habitats to the extent they no longer can support Oregon chub, the probability of that occurring is low given the wide tolerances of this species to water temperatures and corresponding DO levels. The diversity of isolated Oregon chub habitats spread across multiple watersheds provides further buffers against population level impacts from climate change. For these reasons, we determine that temperature effects due to climate change to these “up-slope” habitats do not constitute a substantial threat to Oregon chub now or into the foreseeable future.

Fourteen Oregon chub populations occur on or adjacent to undammed rivers: 13 of these populations are naturally occurring and on or adjacent to rain-dominated, undammed tributaries to the Willamette River (
e.g.,
Marys, Molalla, and Luckiamute Rivers, and Muddy Creek); and 1 population occurs in a spring-fed pond upstream of a USACE dam and thus is unlikely to experience substantial temperature increases or other negative impacts from climate change. For the 13 populations, potential reductions in summer baseflows and associated increases in water temperature are the most likely negative impacts to these populations from climate change effects (including short-term droughts). However, uncertainty in the extent and magnitude of summer baseflow reductions remains high despite modeling efforts (Chang and Jung 2010, pp. 198-202; see following discussion). Given this uncertainty regarding summer baseflow reductions, we cannot predict to what level summer baseflows may drop (and thereby increase water temperatures) and negatively impact these habitats.

We anticipate few of these habitats will be negatively affected to such an extent Oregon chub cannot exist given the high tolerance of Oregon chub to temperature and associated reduced DO levels, the fact that ground water connections to these habitats may remain, and these habitats are distributed across several watersheds with differing influences (Chang and Jung 2010, p. 204). For these reasons, we determine that temperature effects due to climate change in these rain-dominated, undammed tributary habitats do not constitute a substantial threat to Oregon chub now or into the foreseeable future.

The remaining five populations occupy habitats adjacent to USACE reservoirs in the Middle Fork Willamette River: Two populations at Lookout Point Reservoir, two at Dexter Reservoir, and one at Fall Creek Reservoir. Reductions in snow, increases in rain, increased frequency of short-term droughts, instream flow requirements, and related increased water demand for agricultural and municipal uses during droughts may put additional stresses on water supply in the Willamette Basin. These stresses may reduce the USACE's ability to maintain reservoir levels year-round, especially during the late summer and early fall. These reservoir-associated populations are most likely to experience temperature increases, reduced DO levels, and reduction in habitat from loss of connection with the reservoirs, which may occur in the future during predicted short-term droughts. However, we have direct experience with this situation: in 2010, the USACE drew these reservoirs down through the summer of 2011 for dam-safety repairs.

The ODFW monitored these populations closely during and after reservoirs returned to normal levels (Bangs
et al.
2012, p. 18). No populations were lost due to these reduced reservoir levels, despite reduced habitat and high summer temperatures. While some populations experienced a decline the following year, one population increased. Those populations that experienced a decline due to lowered reservoir levels recovered to previous abundance levels (Bangs
et al.
2012, p. 10).

In summary, the Oregon chub is tolerant of a wide range of temperatures and not dependent on cool waters to complete its life history. Oregon chub populations are dispersed across a wide range of diverse habitats, each influenced by site specific factors. The predicted increases in water temperature and associated reductions in DO levels from climate change effects are not anticipated to exceed the tolerances for Oregon chub throughout its range. Also, coordination between the Service and the USACE is required when minimum instream flow requirements wi

[Text truncated at 120,000 characters. The full text is on the page linked above.]

---

Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2015-02951. Public record. Not legal advice.