Stock-specific Run and Escapement of Yukon River Chinook Salmon, 1981-2019 PDF Download

Author: Toshihide Hamazaki
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 48

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Book Description
This report describes a modeling framework to reconstruct the historical time series of drainagewide and stock-specific run and escapement of Pacific salmon Oncorhynchus spp. that return to a single large river system. The model combines historical data from various assessment projects that estimate mainstem passage, harvests, tributary escapements, and stock proportions under a single maximum-likelihood estimation framework. As a demonstration, the modeling framework was applied to reconstruct the historical (1981–2019) drainagewide run size and escapement of Yukon River Chinook salmon (O. tshawytscha) and each of the contributing stock components: Canada, Middle Yukon, and Lower Yukon. The model estimated that the average drainagewide (all stocks) run size was 301,000 (range: 109,000–491,000), escapement was 186,000 (88,000–305,000), and harvest rate was 35% (2–60%). The average Canada stock run size was 125,000 (39,000–214,000), escapement was 60,000 (14,000–126,000), and harvest rate was 48% (2–78%). The average Middle Yukon stock run size was 75,000 (22,000–139,000), escapement was 47,000 (14,000–126,000), and harvest rate was 35% (2–85%). The average Lower Yukon stock run was 101,000 (48,000–204,000), escapement was 78,000 (30,000–164,000), and harvest rate was 21% (1–51%). The next steps regarding the application of this model to Yukon River Chinook salmon should include a comprehensive data review, consideration of alternative model structures, and critical evaluation of model assumptions.