The Independent Scientific Review Panel (ISRP) conducted a review of the Lower Snake River Compensation Plan (LSCRP) steelhead program at the request of the Northwest Power and Conservation Council and U.S. Fish and Wildlife Service. For the review, the ISRP considered annual reports, summary oral presentations, and agency and tribal program reports prepared for the Steelhead Symposium that took place in Clarkston, Washington in June 2012. The format used to evaluate the LSRCP spring Chinook and steelhead program’s accomplishments worked well, and we hope that the same format can be used for the Fall Chinook review. The ISRP believes the data, evaluations, and conclusions provided by the LSRCP steelhead program are applicable beyond the Columbia River Basin and Pacific Northwest. Therefore, we hope that the LSRCP summary report and presentation can serve as a foundation for a scientific paper that assesses the within hatchery and post-release performance of project steelhead.
Two hatchery performance indicators, green egg-to-smolt survival rates and number of smolts released, are universally reported for all the LSRCP steelhead hatchery programs. These two metrics indicate that the performance and practices within the hatcheries are acceptable and meet or exceed stated goals. However, these indicators do not fully summarize hatchery performance. Additional information on parental fish needs to be collected such as numbers used as broodstock and pre-spawning survival, as well as survival, growth, and disease data on their offspring from fertilization through release. Such information is important because it can be used to partition out mortality from collection to final smolt release. Without knowledge of where and when mortality takes place, it is impossible to make adaptive adjustments to hatchery practices. Some of the reports considered by the ISRP contain this information, and in some cases this information is contained in tables within the Hatchery Genetic Management Plans. The ISRP suggests that the LSRCP creates a centralized database for this information that can be updated each year. Such a database can help to identify possible problem areas and indicate where improvements should be focused. Additionally, many clever and innovative methods are used to obtain hatchery performance data. These vary by agency and are perhaps affected by tradition and resource availability. Ideally these methods should be universally shared across all the LSRCP steelhead hatcheries. Perhaps one way of accomplishing this would be to attach documentation of the methods used to the suggested centralized database.
Artificial culture may affect the genetic diversity of cultured stocks and, if straying or integrated hatchery programs occur, natural populations as well. Estimates of the effective population size of hatchery stocks are provided in some of the reports the ISRP received. Tracking temporal changes in effective population sizes, effective number of breeders, mean family size, and variance of family size in hatchery and wild populations would increase understanding of the genetic risks of supplementation. Consequently the ISRP encourages the LSRCP to continue, and if possible expand, genetic analyses on hatchery and natural steelhead populations in the future.
Fish performance post-release to return is adequately reported. High straying rates of some adults, residualism or residency of released smolts, and difficulties in estimating harvest and straying rates remain as post-release problems. A multi-year experiment that compared straying and survival rates of steelhead released from acclimation ponds and directly planted without acclimation showed that fish released from acclimation ponds had lower straying rates and higher smolt-to-adult survival (SAS) rates. Once this was known, another multi-year experiment took place. This time the effects of forced and volitional releases from acclimation ponds were compared. No differences were detected in either straying or smolt-to-adult survival rates. However, the use of volitional releases did provide a method of reducing residualism. Many of the fish remaining in the acclimation ponds are maturing males. These fish were removed and used in “put and take” fisheries. These studies along with efforts that evaluate the effects of different broodstocks on straying are helping to reduce this problem. The LSRCP is to be commended for supporting and performing this work. The ISRP encourages the LSRCP to design studies on the relationships between straying and stress just prior to or during smoltification. Results from such work may provide additional approaches to further reduce straying.
Problems with estimating the straying and harvest rates of project fish were candidly presented. The straying rates presented are underestimates because not all fisheries or natural spawning areas can be sampled. Harvest rates in the lower Columbia and in the project area are also challenging to estimate, mainly because of difficulties in identifying the origin of harvested fish. The LSRCP is investigating the promising approach of using Parent Based Tagging (PBT) to resolve these issues. The application of coded wire tags, PIT tags, and other marks and tags on project fish should continue to provide a means of estimating assignment error rates to the genetically based PBT method.
Fifteen years ago during a previous review of the LSRCP steelhead program, a question was raised about “whether harvest mitigation programs and wild stock recovery can be conducted/achieved concurrently.” This question remains as relevant today as when it was first asked. Numerous risk aversion strategies have been employed by LSRCP steelhead projects to reduce potential interactions between project fish and wild steelhead and other native fishes. Among these are 1) releasing project fish below areas of natural steelhead production, 2) reducing the number of smolts released, 3) using acclimation ponds and volitional exit strategies to reduce straying and residualism, 4) creating refuge areas for natural steelhead, 5) removing hatchery adults at weirs and traps, and 6) developing endemic broodstocks. It appears that the effects of these and other implemented strategies have not been quantitatively assessed. The ISRP believes that measuring possible demographic and genetic impacts of supplementation on the wild steelhead populations in the lower Columbia River and project area represents the next big challenge for the LSRCP program. The ISRP encourages the LSRCP to investigate approaches to modify or develop new methods to assess supplementation impacts. Understanding how the existing hatchery program is influencing the genetic composition and demographic profiles of wild steelhead will help shape how the program proceeds in the future.
See the full report for details and comments on the individual steelhead programs.