Review of the Lower Snake River Compensation Plan’s Spring Chinook Program

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The Independent Scientific Review Panel (ISRP) conducted a review of the Spring Chinook Hatchery Program of the Lower Snake River Compensation Program at the request of the Northwest Power and Conservation Council and U.S. Fish and Wildlife Service, based on annual reports, summary oral presentations, and agency and tribal program reports prepared for the spring Chinook Symposium in November 2010 in Boise, Idaho. The format used to provide an independent retrospective evaluation of the accomplishments of the LSRCP spring Chinook program worked well. The ISRP believes the data, evaluations, and conclusions provided by the LSRCP spring Chinook program are applicable beyond the Columbia River Basin and Pacific Northwest and encourages use of the roll-up report as the foundation to develop a scientific paper on assessing hatchery performance.

Overall, the performance and practices within the hatchery were acceptable and met stated goals. However, information was lacking on broodstock collection goals and no summary was given of differences among the hatcheries (or within years in a hatchery) in fish culture practices such as acclimation versus direct release, on-site versus satellite facility release, rearing densities, nor size and timing at release that might contribute to explaining differences in the performance of smolts after release.

Fish performance post-release to return has been adequately reported. Post-release survival and abundance of hatchery fish has been below expectations. An analysis of survival of smolts after passing Lower Granite Dam was not included in the reports. Smolt to Adult Survival (SAS), and Smolt to Adult Return (SAR) goals (the primary mitigation goals) and the assumptions behind them were overly optimistic. The LSRCP spring Chinook program has not achieved adult production goals to the Columbia River mouth, or to the project area, in any year.

Since the mid-1990s, the LSRCP has included conservation objectives using captive broodstock and supplementation protocols. Assessment of supplementation in the Imnaha River using a Before After Control Impact (BACI) analysis of the abundance of natural origin returns indicated that, when contrasted to nine unsupplemented reference locations, the Imnaha River spring Chinook showed decreased natural origin return abundance post-supplementation relative to five reference sites, and increased abundance post-supplementation relative to four reference sites. The BACI analysis found that productivity (recruits per spawner) in the Imnaha River had decreased relative to all nine unsupplemented sites. The ISRP recommends that the BACI method (or alternatives of similar statistical validity) be used at all locations that have programs that plan to use returning hatchery fish to spawn in the streams.

Density-dependent survival in many of the LSRCP watersheds was a factor constraining the increase in smolt production that was expected from increased spawner abundance in the streams. Managers need to periodically evaluate the carrying capacity of the freshwater environment and adjust hatchery releases accordingly, with fewer releases when carrying capacity is diminished. Most of the hatchery programs were self-sustaining. At least one adult female returned to the hatchery or tributary weir from the spawning of an adult female in the hatchery.

Recently, there has been a Hatchery Scientific Review Group (HSRG) review of the LSRCP hatchery programs. Although the LSRCP reports and presentations identified some HSRG recommendations, in general they did not elaborate sufficiently on the recommendations from those reviews and how they were being addressed by the co-managers. Several of the supplementation programs have moved to sliding-scale broodstock management, where the proportion of hatchery-origin adult fish used for broodstock and permitted on the spawning grounds is increased in the absence or low abundance of wild broodstock. Implementing conservation/supplementation programs using sliding-scale broodstock management where, over the long-term (decades), the hatchery broodstock has little gene flow from the natural population, but the natural population has a large proportion of hatchery-origin adults, is inconsistent with the scientific framework guidance on the operation of an integrated hatchery program. Operating these programs using the sliding scale over many years carries a high risk that both abundance and productivity of naturally spawning stocks will decrease.

The ISRP recommends that managers take action wherever needed to rapidly establish natural populations that are viable. The LSRCP needs to integrate information on the status of the natural populations and their habitat into an adaptive management framework that will inform what should or should not be done within the hatchery programs to enhance the natural populations. This may include reductions in hatchery releases that mix with natural populations or possible increases in hatchery production to mitigate harvest – a delicate balance.

See the attached report for full details.

This should be considered the ISRP final review of the Spring Chinook Program. Originally there was discussion of a response loop, but during development of the individual report reviews the ISRP determined it would be most appropriate to include the findings, conclusions, and recommendations in one report, so the LSRCP co-managers would have those in hand when deciding how they wish to proceed with report revisions for a symposium proceedings. It is the ISRP’s understanding that its report will be incorporated in the symposium proceedings.