Steelhead Kelt Reconditioning and Reproductive Success: 2011 Annual Report
Iteroparity, the ability to repeat spawn, is a natural life history strategy expressed by some species from the family Salmonidae. Observed iteroparity rates for steelhead Oncorhynchus mykiss in the Columbia River Basin are currently depressed due to anthropogenic development which includes: operation of the hydropower system and other habitat degradations. Reconditioning post-spawned fish (kelts) in a captive environment to encourage reinitiating feeding, growth, and redevelopment of gonads is evaluated in this study as an approach to restore depressed steelhead populations. To test the efficacy of utilizing steelhead kelt as a management and recovery tool, different scenarios were investigated ranging from little intervention (collect and return fish to river) to high intensity (collect and feed fish in captivity until rematuration). Transport of Yakima and Snake River steelhead resumed with an attempt to move kelts around dams to improve survival, with results suggesting kelts suffer the highest rates of mortality in the upper estuary and return rates to Bonneville Dam averaging 4.4%. We investigated diet supplementation using pellets top dressed with cyclopeeze and menhaden oil in one treatment, spirulina and pellets in a second diet and the standard pellet diet. We found a significant relationship (χ2 test p=0.0022) between diet treatment and fish movement past Prosser Dam. Fish detected migrating upriver after release comprised 30% of standard diet fish, 42% of spriulina diet fish, and 77% of the cyclopeeze and menhaden diet fish. Comparisons of gamete and progeny viability found that Skamania steelhead kelts produced on average +900 eggs with a small decrease in fertilization (-11%) with the kelt progeny increasing in both weight (+.07g) and length (+.2cm), winter steelhead also had increases in all categories of egg production (+250), fertilization (.3%), progeny weight (.11g), and progeny length (.4cm). Four juvenile steelhead collected in the Yakima River were assigned back to kelt parents released in the fall of 2010. Successful reproduction has been confirmed for four of the nine reconditioned kelts that were detected returning to Omak Creek. Forty-three kelt steelhead were collected at two Clearwater River tributaries and acoustically tagged. All of these tagged fish were detected migrating below the mouth of the Clearwater River at Lewiston, Idaho, and 34 (79%) were detected in the Lower Granite Dam forebay. Feed restriction trials conducted on rainbow trout confirmed that feed availability in post-spawned female rainbow trout negatively impacts the reproductive cycle. Plasma estradiol and vitellogenin hormone levels are being compared to determine their effectiveness at assessing maturation status. The efficacy of ivermectin gavage versus emamectin benzoate injection was investigated to determine which had the best improvement in survival, which we found that emamectin benzoate was the more effective treatment for copepods without the potential for mortality related to ivermectin toxicity. Using genetic stock identification, we found that the majority of kelts collected at Lower Granite Dam were comprised of the Lower Salmon and Grande Ronde rivers stocks, but that all stocks were represented in sampling. Lastly, work on a Snake River Basin steelhead kelt management plan continued.
Hatch, D., R. Branstetter, J. Stephenson, A. Pierce, J. Whiteaker, and B. Bosch. 2012. Steelhead kelt reconditioning and reproductive success. 2011 Annual Report to the U.S. Dept. of Energy, Bonneville Power Administration, Project No. 2007-401-000. Columbia River Inter-Tribal Fish Commission Technical Report 12-13. Portland, OR. 279p.