Commercial Salmon Fisheries
Taku River Fishwheels - Coho Counts

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Fish wheels on the Taku River are an essential platform for the coho salmon mark-recapture program, which provides inseason and postseason escapement estimates. Because fish wheel catchability can be affected by factors such as water level, fish size, abundance, daily spin time, etc., daily fish wheel catches do not necessarily have a meaningful relationship with upriver abundance. In 2018 fishwheel operation protocols were revised and now spin 18 hours a day instead of 24 hours.

Using the mark-recapture data for Taku River coho salmon available through September 13 (Day 3, SW38), the inriver run past Canyon Island in the lower Taku River was estimated. In total, 2,241 tags were released as part of Event 1 of a two-event mark-recapture study, and after adjusting for travel time and assumed sulking, 2,082 (=n1) of these tags were considered available for recapture. This adjusted Event 1 release total coupled with the Event 2 totals of 7,503 (=n2) fish that were examined in the Canadian gillnet fishery and the 289 (=m2) tags that were recovered, were the basic inputs used in this week's mark-recapture estimate.

Use of a Pooled Peterson estimate could not be justified as chi-squared tests indicated complete mixing of tagged and untagged fish did not occur between Event 1 and Event 2 (P=0.01) and equal proportions of tags were not recovered in Event 2 (P<0.001). Thus, a stratified Darroch estimate was used to estimate an inriver run of 54,203 fish (SE = 2,920) past Canyon Island. This, coupled with the estimated 6,200 Canadian-origin Taku River coho salmon that were harvested in the U.S. District 111 terminal drift gillnet fishery through SW38, results in a terminal run estimate of 60,425 coho salmon through September 13. Historically 74% of the run is past Canyon Island by September 13 so this terminal run estimate projects to a final terminal run of 83,283 coho salmon.

The current projected terminal run estimate is below the preseason forecast of 87,000 fish. The Canadian-Origin Taku River coho salmon biological escapement goal range is 50,000 to 90,000 fish with a management objective of 70,000 fish.

Chilkoot Lake Weir | Chilkat Lake Weir | Chilkat River Fishwheels | Hugh Smith Weir
Redoubt Lake Weir (Sockeye) | Situk (Lower) Weir (Chinook) | Situk (Lower) Weir (Sockeye) | Taku River Fishwheels (Sockeye)
Taku River Fishwheels (Coho)