The Use of a Columbia Basin Adult Sockeye PIT Tagging Program to Assess Differences in Stock-Specific Upstream Migration Run Timing and Survival

Columbia Basin sockeye salmon consist of stocks with different habitats and abundances.  The Okanagan stock rears in the eutrophic Osoyoos Lake and has recently produced record escapements.  Meanwhile sockeye rearing in oligotrophic Snake Basin lakes have mean annual escapements of fewer than 1,000 fish and are protected by the Endangered Species Act.  The Lake Wenatchee stock has had escapements ranging from 2,600 to 35,800 over the past ten years.  These differences make lower river harvest management difficult as the desire of fishers to harvest the abundant Okanagan stock is countered by the presence of less abundant stocks. 

 PIT tagging sockeye salmon at Bonneville Dam since 2006 has provided stock-specific data on run timing and upstream survival, supplemented with genetics data since 2012.  However there appears insufficient difference in run timing to manage on a stock-specific basis.  Combined genetics and PIT tag results in 2012 suggested that Wenatchee stock sockeye salmon had a 15% lower upstream migration survival than Okanagan sockeye.  We found no difference in 2013, although fisheries data suggests a higher harvest rate on the Wenatchee stock.  Snake River sockeye in both 2012 and 2013 had lower survival rates than the other stocks, but sample sizes were very low.