*U.S. Dept Commerce/NOAA/NMFS/NWFSC/Publications*

----

### NOAA Technical Memorandum NMFS-NWFSC-24

----

*NOAA-NWFSC Tech Memo-24: Status Review of Coho Salmon*

----

**CONTENTS**

- Executive Summary 
- Acknowledgments
- Introduction      
Scope and Intent of the Present Document
Key Questions in ESA Evaluations 
The  Species  Question
The  Extinction Risk  Question 
Summary of Information Presented by the Petitioners 
Distinct Population Segments 
Population Abundance 
Causes of Decline for Coho Salmon

- Information Relating to the Species Question 
Environmental Features
Physical Features of the Freshwater Environment
Vegetation 
Upwelling
Zoogeography 
Other Ecological Factors
Coho Salmon Life History 
Age 
Fecundity  
Smolt Size and Outmigration Timing
Adult Run Timing
Spawner Size 
Ocean Migration 
Disease 
Clackamas River Late-Run Coho Salmon 
Genetics 
Previous Genetic Studies
New Data
Discussion and Conclusions on ESU Determinations
Reproductive Isolation
Ecological/Genetic Diversity
Conclusions
Additional comments
Artificial Propagation
Patterns of Artificial Propagation and Stock Transfers 
Run Timing
Juvenile Outplants

- Assessment of Extinction Risk 
Background
Absolute Numbers
Historical Abundance and Carrying Capacity 
Trends in Abundance
Factors Causing Variability
Threats to Genetic Integrity 
Recent Events
Other Risk Factors
Approach 
Quantitative Methods
Data Types
Computed Statistics
Analyses of Extinction Risk by ESU
1) Central California Coast
2) Southern Oregon/Northern California Coasts
3) Oregon Coast
4) Lower Columbia River/Southwest Washington Coast 
5) Olympic Peninsula
6) Puget Sound/Strait of Georgia
Conclusions
1) Central California Coast
2) Southern Oregon/Northern California Coasts
3) Oregon Coast
4) Lower Columbia River/Southwest Washington Coast 
5) Olympic Peninsula
6) Puget Sound/Strait of Georgia 

- Citations
- Appendix A:  Glossary
- Appendix B - Environmental Information
- Appendix B-1:  Gauging Stations
- Appendix B-2:  Sampling Stations
- Appendix C - Life History Trait Information
- Appendix C-1:  Smolt Outmigration Timing
- Appendix C-2:  Coho Salmon Smolt Sizes
- Appendix C-3:  River Entry Timing of Coho Salmon
- Appendix C-4:  Coho Salmon Spawn Timing
- Appendix C-5:  Coho Salmon Spawner Sizes
- Appendix C-6:  Marine Recoveries of Coded-wire Tags
- Appendix D:  Personal Communication and Unpublished Information          
- Citations and Questionnaire Responses
- Appendix E - Records of Hatchery Outplants
Appendix E-1: Releases of fry and yearlings in selected Washington and Oregon river basins
Appendix E-2: 
Releases of adults in selected Oregon river basins

----

#### EXECUTIVE SUMMARY

     In October 1993, in response to three petitions seeking protection for coho salmon under theESA, NMFS initiated a status review of coho salmon in Washington, Oregon, and California, and formed aBiological Review Team (BRT) to conduct the review.  This report summarizes biological andenvironmental information gathered in that process.

####  Proposed Coho Salmon ESUs

                                         The BRT examined genetic, life history, biogeographic, geologic, and environmentalinformation to identify where ESU boundaries should be located.  In particular, physical environmentand ocean conditions/upwelling patterns, estuarine and freshwater fish distributions, and coho salmonriver entry and spawn timing and marine coded-wire-tag recovery patterns were found to be the mostinformative for this process.  Based on this examination, the BRT identified six coho salmon ESUs inWashington, Oregon, and California.  The geographic boundaries of the six proposed ESUs are asfollows:

-  Central California coast.  The geographic boundaries of this ESU extend from Punta Gorda innorthern California south to and including the San Lorenzo River in central California, and includetributaries to San Francisco Bay, excluding the Sacramento-San Joaquin River system.  
-  Southern Oregon/northern California coasts.  This ESU includes coho salmon from Cape Blancoin southern Oregon to Punta Gorda in northern California.  
-  Oregon coast.  This ESU covers coastal drainages along most of the Oregon coast from CapeBlanco to the mouth of the Columbia River.  
-  Lower Columbia River/southwest Washington coast.  Historically, this ESU probably includedcoho salmon from all tributaries of the Columbia River below the Klickitat River on the Washington sideand below the Deschutes River on the Oregon side (including Willamette River as far upriver as theWillamette Falls), as well as coastal drainages in southwest Washington between the Columbia River andPoint Grenville (between the Copalis and Quinault Rivers).  
-  Olympic Peninsula.  The geographic boundaries of this ESU are entirely within Washington,including coastal drainages from Point Grenville to and including Salt Creek (directly west of theElwha River).  
-  Puget Sound/Strait of Georgia.  This ESU includes coho salmon from drainages of Puget Soundand Hood Canal, the eastern Olympic Peninsula (east of Salt Creek), and the Strait of Georgia from theeastern side of Vancouver Island and the British Columbia mainland (north to and including Campbelland Powell Rivers), excluding the upper Fraser River above Hope.

####  Assessment of Extinction Risk

                                         The ESA (section 3) defines the term  endangered species  as  any species which is in danger ofextinction throughout all or a significant portion of its range.   The term  threatened species  isdefined as  any species which is likely to become an endangered species within the foreseeable futurethroughout all or a significant portion of its range.   According to the ESA, the determination whethera species is threatened or endangered should be made on the basis of the best scientific informationavailable regarding its current status, after taking into consideration conservation measures thatare proposed or are in place.  In this review, the BRT did not evaluate likely or possible effects ofconservation measures and, therefore, did not make recommendations as to whether identified ESUsshould be listed as threatened or endangered species; rather, the BRT drew scientific conclusionsabout the risk of extinction faced by identified ESUs under the assumption that present conditionswill continue.  The resulting conclusions for each ESU follow.

-  Central California coast.  There was unanimous agreement among the BRT that naturalpopulations of coho salmon in this ESU are presently in danger of extinction.  The chief reasons forthis assessment were extremely low current abundance, especially compared to historical abundance,widespread local extinctions, clear downward trends in abundance, extensive habitat degradation andassociated decreased carrying capacity, and a long history of artificial propagation with the use ofnon-native stocks.  In addition, recent droughts and current ocean conditions may have further reducedrun sizes.  
-  Southern Oregon/northern California coasts.  There was unanimous agreement among the BRTthat coho salmon in this ESU are not in danger of extinction but are likely to become endangered in theforeseeable future if present trends continue.  Current run size, the severe decline from historicalrun size, the frequency of local extinctions, long-term trends that are clearly downward, degradedhabitat and associated reduction in carrying capacity, and widespread hatchery production usingexotic stocks are all factors that contributed to the assessment.  Like the central California ESU,recent droughts and current ocean conditions may have further reduced run sizes.  
-  Oregon coast.  The BRT concluded that coho salmon in this ESU are not in danger of extinctionbut are likely to become endangered in the future if present trends continue.  The BRT reached thisconclusion based on low recent abundance estimates that are 5-10% of historical abundance estimates,clearly downward long-term trends, recent spawner-to-spawner ratios that are below replacement,extensive habitat degradation, and widespread hatchery production of coho salmon.  Drought and currentocean conditions may have also reduced run sizes.  
-  Lower Columbia River/southwest Washington coast.  Previously, NMFS concluded that it couldnot identify any remaining natural populations of coho salmon in the lower Columbia River (excludingthe Clackamas River) that warranted protection under the ESA.  The Clackamas River produces moderatenumbers of natural coho salmon.  The BRT could not reach a definite conclusion regarding therelationship of Clackamas River late-run coho salmon to the historic lower Columbia River ESU. However, the BRT did conclude that if the Clackamas River late-run coho salmon is a native run thatrepresents a remnant of a lower Columbia River ESU, the ESU is not presently in danger of extinctionbut is likely to become so in the foreseeable future if present conditions continue.        For southwest Washington coho salmon, uncertainty about the ancestry of coho salmon runs givenhigh historical and current levels of artificial production prevented the BRT from reaching a definiteconclusion regarding the relationship between coho salmon in that area and the historical lowerColumbia River/southwest Washington ESU.  If new information becomes available, the relationship andstatus of the ESU will be reexamined.   
-  Olympic Peninsula.  While there is continuing cause for concern about habitat destructionand hatchery practices within this ESU, the BRT concluded that there is sufficient native, natural,self-sustaining production of coho salmon that this ESU is not in danger of extinction and is notlikely to become endangered in the foreseeable future unless conditions change substantially.  
-  Puget Sound/Strait of Georgia.  The BRT was concerned that if present trends continue, thisESU is likely to become endangered in the foreseeable future.  Although current population abundanceis near historical levels and recent trends in overall population abundance have not been downward,there is substantial uncertainty relating to several of the risk factors considered.  These riskfactors include widespread and intensive artificial propagation, high harvest rates, extensivehabitat degradation, a recent dramatic decline in adult size, and unfavorable ocean conditions. Further consideration of this ESU is warranted to attempt to clarify some of these uncertainties.

#### ACKNOWLEDGMENTS

                                       The status review for west coast coho salmon was conducted by a team of researchers from theNational Marine Fisheries Service (NMFS).  This biological review team relied on information in theEndangered Species Act Administrative Record for West Coast Coho Salmon, which was developed pursuantto this review and includes comments, data, and  reports submitted by the public and by state, tribal,and federal agencies.  The authors acknowledge the efforts of all who contributed to this record,especially the Washington Department of Fish and Wildlife, Oregon Department of Fish and Wildlife,California Department of Fish and Game, U.S. Fish and Wildlife Service, and Northwest Indian FisheriesCommission.

     The biological review team for this status review included:  Peggy Busby, Dr. David Damkaer,Robert Emmett, Dr. Jeffrey Hard, Dr. Orlay Johnson, Dr. Robert Kope (formerly with the SouthwestFisheries Science Center), Dr. Conrad Mahnken, Gene Matthews, George Milner, Dr. Michael Schiewe,David Teel, Dr. Thomas Wainwright, William Waknitz, Dr. Robin Waples, Laurie Weitkamp, Dr. JohnWilliams, and Dr. Gary Winans, all from the Northwest Fisheries Science Center (NWFSC), and GregoryBryant from the NMFS Southwest Region.  Craig Wingert, from the NMFS Southwest Region, and StevenStone, from the NMFS Northwest Regional Office, also participated in the discussions and providedinformation on coho salmon life history and abundance.

     Jason Griffith and Megan Ferguson, students from the University of Washington, wereinstrumental in compiling information on coho salmon hatcheries.  Don Vandoornik and Dave Kuligowski(NWFSC) collected new genetic data for the status review, and Kathleen Neely (NWFSC) provided most ofthe graphics for this document and assisted in the completion of this status review in numerous otherways.

----

Table of Contents