Summary Review of the Lower Snake River Compensation Plan 2011-2014

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See the ISRP's July 8, 2014 presentation to the Council >

This report summarizes the Independent Scientific Review Panel’s (ISRP) review of the Lower Snake River Compensation Plan’s (LSRCP) three hatchery programs. The ISRP completed a review of the spring Chinook program in 2011 (ISRP 2011-14), the steelhead program in 2013 (ISRP 2013-3), and the fall Chinook program in 2014 (ISRP 2014-4). The reviews were requested by the Northwest Power and Conservation Council and U.S. Fish and Wildlife Service.

Scientific foundation: The ISRP found that the LSRCP’s hatchery programs for steelhead and spring and fall Chinook salmon are largely consistent with the scientific foundation, artificial production strategy, and artificial production principles contained in the Council’s Fish and Wildlife Program. Each hatchery program has objectives, including targets for broodstock abundance, egg-to-smolt survival rates, smolt size-at-release, and contributions to fisheries and, in the case of supplementation programs, to natural spawning populations. Adequate monitoring and evaluation programs are in place to ascertain if these objectives and outcomes are realized. Data produced from project experiments are being used to refine how fish are reared, released, and identified. Interactions between hatchery and wild fish are being examined, and methods used to estimate the survival and contribution of project fish to fisheries and natural spawning populations are being employed and refined. Data gaps have been identified, and program activities designed to address these issues are either underway or planned in the future. The hatchery programs have provided substantial fish and wildlife benefits. These have ranged from preventing extinction of natural populations via supplementation and captive broodstock programs to providing valuable recreational and commercial fishery opportunities. Materials presented at symposiums and associated reports covering LSRCP activities demonstrated that the cooperators are dedicated, innovative, and collaborative. The ISRP compliments them for their fine technical performance. 

In-hatchery performance standards for broodstock abundance, pre-spawning survival of broodstock, egg-to-smolt survival, and numbers of released smolts were established for many of the LSRCP hatcheries. Currently, adequate numbers of broodstock are being collected, and mortality prior to spawning has been low. While under artificial culture, fish will experience some mortality during incubation and rearing. Since 1995, egg-to-smolt survival rates in hatcheries have averaged 84% for steelhead and 70 to 80% in Chinook. These high survival rates are indicative of well-run hatchery programs. Goals for smolt size at release have been set, and with some exceptions, the hatchery programs have met these objectives. Each hatchery is programmed to release a fixed number of smolts. Over the past decade, LSRCP hatcheries for spring Chinook, steelhead, and fall Chinook reached their juvenile release goals 36%, 60%, and 70% of the time, respectively. Failure to reach release goals occurred for a variety of reasons, including the desire for reduced rearing densities and greater size at release. In a few instances, water shortages and scarcity of broodstock also limited fish production. 

Post-release performance of hatchery fish was evaluated by examining survival of smolts from release to Lower Granite Dam, calculating smolt-to-adult survival prior to removal from fisheries (SAS) and smolt-to-adult return (SAR) to Lower Granite Dam. Additionally, the number of recruits produced per fish spawned (R/S) was estimated along with harvest numbers and frequency of straying. The survival of smolts to Lower Granite Dam varied from one year to the next but typically ranged from 60 to 70%. Standards for SAS and SAR rates were established for the steelhead and Chinook hatchery programs. Considerable annual variation in SAS and SAR values was observed. Substantial differences in these values occurred among hatcheries rearing the same type of fish; however, they tended to increase or decrease in a synchronous fashion. Consequently, survival of smolts to the adult stage appears to be shaped by conditions the fish experience in the mainstem and ocean. To be self-sustaining, a hatchery needs on average to consistently achieve R/S values that are equal to or greater than 1, and this has been accomplished by all the hatcheries in LSRCP program. One of the primary objectives of the LSRCP was to restore fisheries in areas below and above the project area. Harvest goals for the ocean and mainstem Columbia River originally envisioned for the LSRCP have never been reached. Lower than expected SAS values and the need to constrain fisheries to protect Endangered Species Act (ESA)-listed species are largely responsible. Nevertheless, the hatchery programs have significantly increased the total abundance of spring and fall Chinook and steelhead, and thus the program has contributed to important commercial and recreational fisheries.

Potential demographic, ecological, and genetic impacts of the hatchery programs were assessed. Chinook reared in hatcheries produced more early maturing males and fewer older maturing fish than wild counterparts. Age data were collected over time on hatchery and natural populations of spring Chinook, and no identifiable trend toward an increasing number of younger fish was detected in either group. This result suggests that changes in age observed in hatchery populations were mainly caused by environmental conditions the fish experienced during artificial culture. Nevertheless, naturally spawning hatchery fish influence the age structure of natural populations because they currently represent a high proportion of natural spawners. The ISRP encourages LSRCP cooperators to continue to test and evaluate changes in age structure, including genetic linkages, and its effect on productivity. The migration timing of adult hatchery and natural-origin salmon and steelhead was examined and found to differ in some projects.

New research is examining the spawning distribution of hatchery and natural-origin fish in streams; some hatchery fish formed spawning aggregations adjacent to release locations. Straying of hatchery fish was evaluated annually, and it varied by year and species. In a few cases, straying percentages for project steelhead to out-of-basin watersheds exceeded 20%. After this degree of straying was identified, the LSRCP implemented a number of strategies, including the use of endemic broodstocks and the wide-scale use of acclimation ponds, which reduced the incidence of straying. However, transport of juveniles in barges around the dams remains a key factor contributing to the straying of steelhead. Potential interactions between juvenile hatchery and wild fish were considered and some protocols have been implemented to minimize disease transmission and the possible occurrence of competitive and predaceous interactions.

The effects of supplementation on adult abundance and productivity of natural populations are also being investigated. Results of these studies have been mixed. Spring Chinook supplementation programs have increased the total abundance of spawners in their rivers (hatchery plus wild) but have not produced an increase in natural-origin adults. Fall Chinook supplementation has likely contributed to the recent increases in natural-origin fish abundance in the Snake River Basin, but the productivity of the natural-spawning population remains very low. Clear evidence for density dependence has been observed in supplemented populations, especially in spring Chinook, and this ecological response may inhibit desired increases in abundance and productivity. In fall Chinook, there has been a marked increase in natural-origin fish, and it is reasonable to believe that a number of these represent the progeny of naturally spawning hatchery fish. For logistical reasons, assessing the role of supplementation versus improvements in survival and harvest reductions is not complete. Additional research is needed to understand how genetic and environmental factors, including habitat restoration, affect the consequences of supplementation on natural populations. The LSRCP’s supplementation programs offer important opportunities for such work.

Monitoring and evaluation programs established by the LSRCP have allowed its three hatchery programs to make informed changes to hatchery infrastructure, broodstock sources and collection locations, mating protocols, and rearing and release procedures. Ongoing refinements to run reconstruction procedures are helping to quantify harvest numbers and to estimate natural escapements of project fish. Parentage based tagging will be used in the future to identify all the hatchery steelhead and spring and fall Chinook produced by the LSRCP. Accurate identification of hatchery origin fish will allow additional refinements to 1) the contribution rates of hatchery and natural origin fish to harvests and spawning escapements and 2) estimates of natural origin productivity and abundance.

After Snake River spring and fall Chinook and steelhead were listed by the ESA, the LSRCP recognized the need to assist in the recovery of these species in addition to meeting original program objectives. The ISRP encourages the LSRCP to continue collaborative efforts with ESA recovery planning while also providing the harvest opportunities originally sought by the LSRCP. Overall, the hatchery component of the LSRCP is scientifically sound. It has established goals, quantitative targets, and objectives for research, monitoring, and evaluation. Finally, as indicated above, it has demonstrated the ability to be managed adaptively as new challenges develop.