Distribution and movement patterns of chinook salmon returning to the Yukon River basin in 2000-2002

Abstract

A radio telemetry study was conducted on Yukon River chinook salmon from 2000 to 2002 to provide information on stock composition and timing, migration patterns, and the location of important spawning areas. Feasibility work in 2000-2001 determined that drift gill nets were effective for capturing adequate numbers of fish in the lower river, and that the fish responded well to the capture and tagging procedures based on their subsequent upriver movements.

A large-scale tagging and basin-wide monitoring program was conducted in 2002. Most (751, 97.8%) of the 768 fish tagged resumed upriver movements, with 270 fish harvested in fisheries and 481 fish tracked to upriver areas using remote tracking stations and aerial surveys. Stock composition estimates were developed for the 2002 chinook salmon return based on the distribution of daily releases of radio-tagged fish weighted for abundance and adjusted for fish harvested in fisheries.

The chinook salmon run was composed primarily of Tanana River (20.9%) and upper basin (66.0%) stocks. Canadian-origin fish comprised the largest component of the return (53.4%), with most traveling to reaches of the Yukon River (50.7%) and only small numbers to the Porcupine River (2.7%). Canadian fish in the Yukon River returned to large headwater tributaries (35.5%), small tributaries associated withthe main river (4.6%) and reaches of the Yukon River main stem (10.6%). Chandalar River and Sheenjek River fish (5.9%) were important U.S. stocks in the upper basin. Tanana River fish were predominantly Chena River, Salcha River, and Goodpaster River stocks (18.8%), 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 (3.1%). Fish returning to lower basin tributaries (6.3%) were comprised primarily of Anvik River and Nulato River fish (4.8%).

The two major stock groups, Canadian Yukon River and Tanana River fish, exhibited similar run timing with most fish passing through the lower river during the early and middle runs, although differences within regions were observed. In Canada, chinook salmon returning to the Klondike, Stewart, and White rivers were primarily early run fish, while 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 km/day. Middle and upper basin stocks traveling through reaches of the Yukon River main stem averaged 54-61 km/day, although slower swimming speeds were recorded as the fish approached their natal streams. Movement rates for lower basin stocks were substantially less, averaging from 31 km/day to 37 km/day, possibly due to the shorter distances traveled to reach their spawning areas.


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