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Division: Sport Fish
Title: Seasonal stock contributions of the inriver run and sport harvest for tributary and mainstem spawning Chinook salmon in the Kenai River, Alaska
Author: McKinley, T. R., A. W. Barclay and J. Jasper
Year: 2013
Report ID: Alaska Department of Fish and Game, Fishery Data Series No. 13-64, Anchorage.
Abstract: The goal of this project was to describe the stock composition over the fishing season of the inriver run and sport harvest for Kenai River Chinook salmon by 3 different reporting groups (Lower Tributary, Upper Tributary, and Mainstem) using mixed stock analysis (MSA). Mixture samples from the inriver run were collected during 2003–2013 via an existing netting program as the salmon passed river mile 8.5 in the lower Kenai River; samples from the sport fishery were collected from creel (2006–2013) and roving (2007–2010) sample surveys. MSA results from the inriver run show that Upper Tributary fish were a small but protracted component of the run. Lower Tributary fish accounted for nearly all of the run prior to mid-June, but were near zero after the first week of July. Mainstem fish were not a significant component of the run until mid-June, and comprised nearly all of the run by the first week in July. MSA results from the sport harvest below the Soldotna Bridge demonstrate that prior to 1 July, the majority of the harvest in all stratified time periods in all years (2006–2013) was generally of Lower Tributary fish, but after 1 July, Lower Tributary fish were less than 20% of the harvest. Upper Tributary fish were under 20% of the harvest in all strata prior to 1 July and less than 15% in all strata after 1 July. The Mainstem component of the harvest became 50% or greater within the last June stratum prior to 1 July, and accounted for 75% or more of the harvest in all July strata for all years. MSA results from samples collected above the Soldotna Bridge show that prior to 1 July, the majority of the harvest in all strata in all years (2007–2010) was generally of Lower Tributary fish. In all years, the proportion of Lower Tributary fish peaked in the first stratum and declined in succeeding strata. Mainstem fish and Upper Tributary fish were 25% or less of the harvest in any of the strata prior to 1 July. From 1 July until the end of the season, Lower Tributary fish accounted for 25–50% of the harvest during 1–7 July and less than 25% in all strata after that in all years (2006–2013). Mainstem fish accounted for approximately 35–65% of the harvest during 1–7 July and 70% or greater during later strata. Fish sealed by the Alaska Department of Fish and Game as trophy fish (Chinook salmon 55 inches total length or greater) were primarily from the Mainstem reporting group. These results will be useful in generating estimates of escapement of tributary- and mainstem-bound Chinook salmon, escapement goal analyses for these stocks, as well as estimating harvest in mixed-stock fisheries outside of the Kenai River drainage.
Keywords: Chinook salmon, Oncorhynchus tshawytscha, Kenai River, spawning abundance, age composition, escapement goal, run reconstruction, spawner–recruit analysis, maximum sustained yield, measurement error, serial correlation, missing data, Bayesian statistics, OpenBUGS, mixed stock analysis