Detection of PIT-tagged juvenile salmonids in the Columbia River estuary using pair-trawls, 2005

In 2005, we continued a study to detect juvenile anadromous salmonids Oncorhynchus spp. implanted with passive integrated transponder (PIT) tags using a large surface pair-trawl fitted with a PIT-tag detection antenna. We sampled in the Columbia River upper estuary between river kilometers (rkm) 61 and 83 for 909 h between 20 April and 5 August and detected 14,101 PIT-tagged juvenile salmonids of various species, runs, and rearing types. Not all stocks and rearing types were equally represented in the annual detection totals. For example, ofthe total detections, 18% were wild fish and 79% were hatchery-reared; 64% were Chinook salmon, 32% were steelhead, and the remaining 4% were other salmonid species. Contract no. 56ABNF100030