Baker Matthew R, Kendall Neala W, Branch Trevor A, Schindler Daniel E, Quinn Thomas P
School of Aquatic and Fishery Sciences, University of Washington Seattle, WA, USA.
Evol Appl. 2011 May;4(3):429-43. doi: 10.1111/j.1752-4571.2010.00154.x. Epub 2010 Sep 14.
Fisheries often exert selective pressures through elevated mortality on a nonrandom component of exploited stocks. Selective removal of individuals will alter the composition of a given population, with potential consequences for its size structure, stability and evolution. Gillnets are known to harvest fish according to size. It is not known, however, whether delayed mortality due to disentanglement from gillnets exerts selective pressures that reinforce or counteract harvest selection. We examined gillnet disentanglement in exploited populations of sockeye salmon (Oncorhynchus nerka) in Bristol Bay, Alaska, to characterize the length distribution of fish that disentangle from gillnets and determine whether nonretention mortality reinforces harvest selection and exerts common pressures according to sex and age. We also evaluated discrete spawning populations to determine whether nonretention affects populations with different morphologies in distinct ways. In aggregate, nonretention mortality in fish that disentangle from gillnets counters harvest selection but with different effects by sex and age. At the level of individual spawning populations, nonretention mortality may exert stabilizing, disruptive, or directional selection depending on the size distribution of a given population. Our analyses suggest nonretention mortality exerts significant selective pressures and should be explicitly included in analyses of fishery-induced selection.
渔业常常通过提高死亡率，对被捕捞种群的非随机部分施加选择压力。选择性地移除个体将改变特定种群的组成，对其大小结构、稳定性和进化产生潜在影响。刺网已知会根据鱼的大小进行捕捞。然而，因从刺网中挣脱而导致的延迟死亡是否会施加选择压力，强化或抵消捕捞选择，目前尚不清楚。我们研究了阿拉斯加布里斯托尔湾红大麻哈鱼（Oncorhynchus nerka）被捕捞种群中的刺网挣脱情况，以描述从刺网中挣脱的鱼的长度分布，并确定未被捕捞的死亡率是否强化了捕捞选择，并根据性别和年龄施加共同压力。我们还评估了离散的产卵种群，以确定未被捕捞是否以不同方式影响具有不同形态的种群。总体而言，从刺网中挣脱的鱼的未被捕捞死亡率抵消了捕捞选择，但因性别和年龄而产生不同影响。在个体产卵种群层面，未被捕捞死亡率可能会根据特定种群的大小分布施加稳定、破坏或定向选择。我们的分析表明，未被捕捞死亡率施加了显著的选择压力，应明确纳入渔业诱导选择的分析中。
