Detection of PIT-tagged juvenile salmonids in the Columbia River estuary using pair-trawls, 2009

In 2009, we continued a multi-year study to detectjuvenile anadromous salmonids Oncorhynchus spp. implanted with passive integrated transponder (PIT) tags using a surface pair-trawl fitted with a PIT-tag detection system. We sampled in the upper Columbia River estuary between river kilometers (rkm) 61 and 83 for 1,139 h between 6 March and 12 August, and during this time we detected a total of 23,247 PIT-tagged juvenile salmonids. Ofthese detections, 17% were wild fish and 80% were hatchery (3% were of unknown origin). Oftotal detections by species, 47% were yearling Chinook salmon, 13% were subyearling Chinook salmon, 33% were steelhead, 4% were sockeye, and 3% were unknown species. Contract no. 56ABNF100030