Commercial Harvest of Klawock Lake Sockeye Salmon in the District 103 and 104 Purse Seine Fisheries, Southeast Alaska, 2018–2021

The Klawock Lake sockeye salmon (<em>Oncorhynchus nerka</em>) run supports one of the most heavily used subsistence fisheries in Southeast Alaska and is the primary sockeye salmon subsistence resource for the communities of Klawock and Craig. During the period 2011–2017, the average spawning population declined by 63% and the average reported subsistence harvest declined by 50% compared to the previous decade. A major source of uncertainty regarding the decline in Klawock Lake sockeye salmon abundance is the lack of information regarding harvest in commercial fisheries. This project will provided estimates of the harvest and run timing of Klawock Lake sockeye in nearby commercial purse seine fisheries for four years (2018–2021) through genetic mixed stock analysis of sampled harvests. The commercial fisheries in management Districts 103 and 104 were targeted because they are terminal to Klawock Lake and most of the commercial harvest of Klawock Lake sockeye salmon likely occurs in those districts. We further split District 103 into two spatial strata: Northern District 103 (subdistricts 50-90) and Southern District 103 (subdistricts 11-40). The commercial harvest of Klawock Lake sockeye salmon was highest in Northern District 103 in three of four years (2018–2020), and highest in District 104 in one year (2021). Klawock Lake sockeye were virtually absent in the commercial harvest in Southern District 103 in all four years (2018-2021). The total commercial harvest (Districts 103 and 104) of Klawock Lake sockeye salmon was 2,619 fish in 2018, 5,523 fish in 2019, 3,352 fish in 2020, and 6,677 fish in 2021. These data, combined with escapement and subsistence harvests, were used to produce the first estimates of total run size for Klawock Lake sockeye salmon. The total run size varied from year to year, with 13,147 fish in 2018, 14,953 fish in 2019, 19,702 fish in 2020, and 13,600 fish in 2021. Similarly, overall harvest rates varied from 43.9% in 2018 to 59.9% in 2021 (average = 50.9%). Commercial harvest rates averaged lower than the historical averages from nearby sockeye salmon stocks at Hugh Smith and McDonald Lakes. Commercial harvest rates were higher in odd-years than even-years, presumably due to increased fishing pressure on more abundant odd-year pink salmon. The subsistence harvest rates averaged higher (20.1%) than the subsistence harvest rates on McDonald and Hugh Smith Lakes (average &lt; 2%).克拉瓦克湖红大马哈鱼（sockeye salmon，*Oncorhynchus nerka*）洄游种群支撑着阿拉斯加东南部使用最为广泛的生存型渔业之一，同时亦是克拉瓦克与克雷格社区核心的红大马哈鱼生存型捕捞资源。相较于前一个十年，2011至2017年间，该种群的平均产卵亲体数量下降63%，报告的平均生存型捕捞量则下滑50%。当前制约克拉瓦克湖红大马哈鱼种群丰度衰退评估的核心不确定性因素之一，是商业捕捞环节的相关数据严重缺失。本项目拟通过对采样捕捞样本开展遗传混合种群分析，在2018至2021年的四年周期内，估算克拉瓦克湖红大马哈鱼在邻近商业围网渔业中的捕捞量与洄游时间窗口。研究选定103号与104号管理区的商业渔业作为目标作业区域，原因在于这两个区域为克拉瓦克湖红大马哈鱼的终端捕捞海域，且该种群的绝大多数商业捕捞量均集中于此。我们进一步将103号管理区划分为两个空间分层单元：北部103号管理区（分区50-90）与南部103号管理区（分区11-40）。2018至2020年的三个年度中，克拉瓦克湖红大马哈鱼的商业捕捞量均以北部103号管理区为最高，而2021年则以104号管理区的捕捞量居首。在全部四年的监测周期内，南部103号管理区的商业捕捞样本中几乎未捕获克拉瓦克湖红大马哈鱼。2018至2021年，103号与104号管理区的克拉瓦克湖红大马哈鱼总商业捕捞量分别为2619尾、5523尾、3352尾与6677尾。结合产卵逃逸种群数量与生存型捕捞量数据，本研究首次估算得到了克拉瓦克湖红大马哈鱼的总洄游种群规模。各年度总洄游种群规模存在显著波动：2018年为13147尾，2019年为14953尾，2020年为19702尾，2021年为13600尾。整体商业捕捞率同样存在年度差异，从2018年的43.9%波动至2021年的59.9%，平均捕捞率达50.9%。该商业捕捞率的平均值低于邻近的休·史密斯湖与麦克唐纳湖红大马哈鱼种群的历史平均捕捞率。奇数年的商业捕捞率高于偶数年，推测原因是奇数年粉鲑（pink salmon）种群丰度更高，进而带来了更强的捕捞压力。生存型捕捞率的平均值为20.1%，显著高于麦克唐纳湖与休·史密斯湖的生存型捕捞率（平均不足2%）。