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The Oregon Fish Commission and Washington Department of Fisheries conducted a cooperative winter steelhead trout (Salmo gairdneri) tagging program on the Columbia River during the winters of 1954-55 and 1955-56. Objectives of the program were: (1) to obtain information on the timing of the various segments of the run; (2) to obtain a population estimate; (3) to measure the sport and commercial fishing mortality; and (4) to compare Petersen disc and spaghetti tube tags. Drift and set gill nets were used to capture the fish. The total numbers tagged were 837 in 1954-55 and 3,362 in 1955-56. Mortalities due to gill netting and seals amounted to 343 fish. The principal sources of tag recoveries were the sport fishery, tagging gear, commercial fishery, fishways, and hatcheries. A total of 145 and 632 tags, respectively, were recovered from the two winters of the investigation, or 17.3 and 18.8 percent. Chi-square tests showed a significant difference between the recovery ratios of Petersen disc and spaghetti tube tags from the commercial gill-net fishery and tagging gear. No difference was indicated in the recovery ratios from the tributary sport fisheries or hatcheries and fishways.
The gill nets appeared to exhibit a 2:1 selectivity for Petersen tags. Steelhead were present in the lower Columbia River throughout the winter months, with the largest numbers taken during March in both years. Numbers of tagged steelhead remained or milled in the Columbia River up to 20 days and occasionally a month or more prior to entering the tributaries. The major winter steelhead streams, such as the Cowlitz, Willamette, Sandy, and Lewis Rivers, received recoveries from almost all months of tagging, but the Willamette River was characteristic in that the bulk of recoveries were from the March tagging. The Cowlitz River received a larger proportion of November-February fish. The other rivers showed no particular trend although March was the best month for most streams. The population of winter steelhead entering the Columbia River during 1955-56 was estimated at 217,400 with 95 percent confidence limits of 172,700 to 279,900. The commercial fishery was calculated to have taken between 3 and 5 percent of the run and the sport fishery 13 to 21 percent. |
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