Coho Assessment Part 2: Viability Criteria Final Report May 6, 2005 Oregon Coastal Coho Assessment Part 2: Viability Criteria and Status Assessment of Oregon Coastal Coho State of Oregon1 May 6, 2005 1 For reference purposes, primary authors are Mark Chilcote, Tom Nickelson and Kelly Moore, Oregon Department of Fish and Wildlife, Salem, Oregon. Coho Assessment Part 2: Viability Criteria Final Report May 6, 2005 Table of Contents I. INTRODUCTION.....................................................................................................................................................3 II. POPULATION AND ESU STRUCTURE ........................................................................................................3 III. POPULATION ATTRIBUTES OF FISH PERFORMANCE...................................................................6 IV. CONSIDERATIONS FOR CRITERIA DEVELOPMENT .......................................................................6 ESU STATUS AND FOCUS OF CRITERIA................................................................................................................... 6 CRITERIA DEVELOPMENT OBJECTIVES.................................................................................................................... 7 FISH PERFORMANCE BASED ...................................................................................................................................... 7 EFFECTS OF MARINE SURVIVAL ............................................................................................................................... 8 DENSITY DEPENDENT RECRUITMENT – RESILIENCE AT LOW SPAWNER ABUNDANCE .................................... 9 COHO UNDER STRESS – MARINE SURVIVAL CONDITIONS OF THE 1990S......................................................... 13 V. DESCRIPTION OF POPULATION SPAWNER ABUNDANCE DATA..............................................13 VI. MODELING POPULATION RECRUITMENT.........................................................................................14 BACKGROUND............................................................................................................................................................ 14 RECRUITMENT MODEL – DENSITY DEPENDENT POPULATION GROWTH RATE.............................................. 15 ALTERNATE RECRUITMENT MODEL – DENSITY INDEPENDENT GROWTH RATE............................................. 19 VII. POPULATION CRITERIA DESCRIPTION AND RATIONALE......................................................20 CRITERIA 1 – SPAWNER ABUNDANCE .................................................................................................................... 20 CRITERIA 2 – PRODUCTIVITY.................................................................................................................................. 22 CRITERION 3 – LONG-TERM PERSISTENCE ............................................................................................................ 26 CRITERION 4 – WITHIN POPULATION DISTRIBUTION........................................................................................... 29 CRITERION 5 – WITHIN POPULATION DIVERSITY................................................................................................. 36 SUMMARY OF POPULATION CRITERIA AND EVALUATION THRESHOLDS.......................................................... 40 VIII. INTEGRATION OF POPULATION CRITERIA FOR ESU EVALUATION...............................41 IX. APPLICATION OF CRITERIA - OREGON COASTAL COHO .........................................................42 POPULATION RESULTS.............................................................................................................................................. 42 X. ADDITIONAL CONSIDERATIONS..............................................................................................................44 KEY ASSUMPTIONS AND ANALYTICAL PROTOCOL FOR POPULATION CRITERIA............................................. 45 DATA QUALITY AND MEASUREMENT ERROR....................................................................................................... 47 ASSUMED FUTURE CONDITIONS AND IMPACT ON ASSESSMENT FINDINGS...................................................... 54 FUTURE DETECTION OF ADVERSE CHANGES IN ESU STATUS........................................................................... 58 XI. SYNTHESIS AND SUMMARY OF EVALUATION RESULTS ...........................................................59 XII. REFERENCES ....................................................................................................................................................62 APPENDIX 1 ................................................................................................................................................................68 APPENDIX 2 ................................................................................................................................................................69 2 Coho Assessment Part 2: Viability Criteria Final Report May 6, 2005 I. Introduction Populations of coho salmon (Oncorhynchus kisutch) that occur in coastal watersheds between Cape Blanco and the mouth of the Columbia River are being evaluated by NOAA Fisheries for listing under the federal Endangered Species Act (ESA). These populations are designated as a single Evolutionary Significant Unit (ESU) (Weitkamp et al. 1995). Oregon, in partnership with NOAA Fisheries, initiated a collaborative project to address the conservation of coastal coho. Assessing the status of coastal coho relative to viability criteria is a vital step in this process, and the focus of Part 2 of this report. Where possible and when available, technical products for the viability assessment were used from the Oregon Coastal Coho Technical Recovery Team (TRT), which is in the process of developing technical products for a recovery plan. Other technical products were developed internally by Oregon. There are five primary components of the viability analysis, which also serve as the primary organizational structure of this report: 1. Determination of the ESU, strata and population structure; 2. Description of attributes used to define viability and assess fish status; 3. Development of specific criteria for each attribute used to define population viability; 4. Development of specific criteria for strata and ESU viability based on roll-up of population criteria; and, 5. Assessment of current status of coastal coho relative to population, strata and ESU viability criteria based on the key attributes described in 2. II. Population and ESU Structure The conceptual foundation for the biological criteria drew heavily from conservation principles for salmon and steelhead presented by McElhany et al. (2000) in their publication entitled Viable Salmonid Populations (VSP). This approach is based on the idea that the overall conservation condition of an ESU can be stated in terms of the distribution and frequency of viable populations within the ESU. Essentially, the viability of individual populations becomes the basic unit of salmon conservation. Therefore, to initiate this type of assessment it is necessary to first breakup the ESU into individual populations. For this assessment, population definitions and associated geographical boundaries were the same as those developed by the Oregon Working Group of the Coastal Coho Technical Recovery Team (OTRT). The OTRT’s rationale for population boundary delineation is described by Lawson et al. (2004). However, the list of populations has been recently modified by the OTRT primarily to incorporate new information about the Umpqua basin. These recent modifications are included in the Oregon Plan assessment and are reflected in the list of populations provided in Table 1. 3 Coho Assessment Part 2: Viability Criteria Final Report May 6, 2005 Table 1. List of populations and associated strata for that constitute the Oregon coastal coho ESU. Functionally Potentially Geographic Independent Independent al Strata Populations Populations Dependent Populations North Coast Nehalem Necanicum Arch Cape Netarts Short Sand Nestucca Ecola Rover Spring Tillamook Neskowin Sand Watseco Mid-Coast Alsea Beaver Berry Cummins Johnson (Siletz) Siletz Salmon Big Depoe Bay Schoolhouse (Alsea) Siuslaw Big Devils Lake Spencer (Siuslaw) Yaquina Big Fogarty Tenmile (Yaquina) Creek Bob Moolack Thiel Cape Rock Vingie China Rocky Wade Coal Yachats Lakes Siltcoos Sutton Tahkenitch Tenmile Umpqua Lower Middle Umpqua Umpqua South Umpqua North Umpqua Mid-South Coquille Coos Johnson Coast (Coquille) Floras Threemile Sixes Twomile In the most recent iteration, the OTRT has identified 57 populations of Oregon coastal coho. Thirty-six of these populations are classified as dependent, meaning they likely have been too small to persist for long periods (i.e., 100 years) without substantial reproductive support provided by strays from larger and more stable adjacent populations (Lawson et al. 2004). As such, these dependent populations were not used for development of viable criteria and the population and ESU assessment. The remaining 21 populations are larger and, at least historically, were more likely to persist over the long-term. These larger populations are referred to as independent populations and their location within the ESU illustrated in Figure 1. However, within this classification a further distinction is made between a “functionally independent” population and a “potentially independent” population. A “functionally