Stock Composition, Run Timing, and Movement Patterns of
Chinook Salmon Returning to the Yukon River Basin in 2004

Abstract

A radio telemetry study was conducted on Yukon River Chinook salmon (Oncorhynchus tshawytscha) during 2004 to provide information on stock composition and run timing, migrationpatterns, and locations of important spawning areas. A total of 995 fish were radio tagged in thelower Yukon River near the village of Russian Mission. After tagging, most (958, 96.3%) fish resumed upriver movements, with 329 fish harvested in fisheries and 629 fish tracked to upriverareas using remote tracking stations and aerial surveys. Stock composition estimates were developed for the 2004 return based on the distribution of daily releases of radio-tagged fish weighted by daily measures of abundance and adjusted for fish harvested in fisheries. The Chinook salmon run was composed primarily of Tanana River (24.4%) and upper basin (55.2%)stocks. Canadian-origin fish comprised a substantial proportion of the return (47.5%), with most traveling to reaches of the Yukon River (46.2%) and only small numbers to the Porcupine River(1.3%). Yukon River fish in Canada returned to large headwater tributaries including the Stewart, Pelly, Big Salmon, and Teslin rivers (27.3%), small tributaries associated with the main river (8.2%), and reaches of the Yukon River main stem (10.7%). Chandalar and Sheenjek Riverfish (2.9%) were the principle U.S. stocks in the upper basin. Tanana River fish were predominantly Chena, Salcha, and Goodpaster River stocks (17.9%), with small populations located in other tributaries. Middle basin fish traveling to the Koyukuk, Melozitna, Nowitna, and Tozitna rivers were a minor component of the run (5.5%). Stocks returning to lower basin tributaries (7.6%) were primarily Bonasila, Anvik, and Nulato River fish (7.1%). The two major stock groups, Canadian Yukon River and Tanana River fish, exhibited similar run timing with most fish passing through the lower river in mid-June, although several distinct pulses were also observed in early June and late June-early July. In Canada, upper headwater stocks displayed a later and more protracted run timing. Lower basin stocks consisted primarily of late run fish,although other stocks, particularly Canadian Yukon River fish, were also present during this period. Movement rates for radio-tagged fish averaged 51.8 km/day. Middle and upper basin stocks averaged 46.4 km/day and 55.1 km/day, respectively. However, these stocks exhibited comparable movement rates in reaches of the Yukon River main stem, while slower swimming speeds were recorded as the fish approached their natal streams. Movement rates for lower basin stocks were substantially less, averaging from 34.6 km/day, possibly due to the shorter distances traveled to reach their spawning areas.


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