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.
Taku River coho salmon stock assessment was complete for the 2021 season on October 2nd. Using the available stock assessment data for Taku River coho salmon, a bilateral estimate of inriver run size has been developed through SW40-4, the last day of tag recoveries. Through Wednesday, September 29 (Day 4, SW40), 10,874 fish have been examined for marks and 180 marks have been recovered. Assuming a sulk rate of 3 days, a total of 1,384 tags were released through September 26 (Day 1, SW40). Applying these values to a Stratified Darroch yields an inriver run estimate of 85,800 (SE = 6,589) fish. Complete mixing (P<0.19) of tagged and untagged fish and equal probability of capture (P=0.20) between release and recapture locations was not significantly different. Expanding by the average run timing (99% through September 29) yields a projected inriver run estimate of 86,406 fish. An estimate of 7,900 Canadian-origin Taku River coho salmon have been harvested in the D11 US terminal drift gillnet fishery through SW40. Combining the projected inriver run estimate of 86,406 fish with the expanded D11 US terminal harvest of Canadian-origin Taku River coho salmon, generates a terminal run estimate of 94,300 coho salmon.
The final inseason projected terminal run estimate is consistent with the preseason forecast of 94,000 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.
This is the final Canadian-origin Taku River coho salmon inseason estimate for the 2021 season. The stock assessment components of the above estimates are preliminary. Final estimates of run strength will be developed later this fall and winter as data becomes finalized.