Columbia River Alternative Gear Studies: Preliminary Survival Estimates of
Steelhead Caught and Released in Commercial Purse and Beach Seines
Josh Holowatz 1 & Dan Rawding 2
(1)Josh Holowatz (presenter): WDFW, Region 5, 2108 Grand Blvd., Vancouver, WA
98661 (360)906-6771 Josua.Holowatz@dfw.wa.gov
(2) Washington Department of Fish and Wildlife
Columbia River commercial fisheries targeting salmon incidentally catch steelhead and fishers are required to release all steelhead back into the river. During the summer and fall fisheries, gill nets are used to catch salmon. Although not empirically measured for steelhead, their release survival from these fisheries is believed to low. This is an important issue since all summer steelhead populations in the Columbia River are listed for protection under the Endangered Species Act. In
2011, the Washington Department of Fish and Wildlife (WDFW) in cooperation with local fishers evaluated a purse and beach seining program to estimate the survival of released steelhead using Passive Integrated Transponder (PIT) tags. A second group of steelhead was PIT tagged at the Bonneville (BON) Dam fish collection facility and transported downstream to an area adjacent to the fishery to serve as a control. A total of 459 fish were tagged in the BON ladder and 543 seined fish were tagged. Using contingency table analysis with a significance level of 0.05, there was no difference in recapture probabilities to BON between purse and beach seine fish and these groups were pooled for further analysis. There was no difference in the recovery probabilities of seined and control fish to BON. Using Ricker’s two release method, survival of seined fish was estimate to be 97.9% with 95% CI from 95.4% to
99.8%. There was a 98.9% probability that the survival of seined fish exceeded
95%. Longer-term survival will not be evaluated until the summer of 2012 after tagged steelhead have completed their spawning migration.