Data from: Genetic stock composition of marine bycatch reveals disproportional impacts on depleted river herring genetic stocks

Bycatch of mid-trophic level anadromous fishes that connect marine and freshwater ecosystems is a growing conservation concern. Anadromous alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis) are important components of coastal freshwater and marine food webs, but have experienced dramatic declines in the abundances of spawning adults. Freshwater-focused restoration efforts have yielded few consistent signs of recovery; raising concerns that bycatch in Northwest Atlantic commercial fisheries may be negating these conservation actions. Using data from 15 microsatellites genotyped for baseline populations and bycatch, we conducted genetic stock identification to understand how bycatch was partitioned among previously identified regional genetic stocks. We then combined this information with fishery observer data to estimate genetic stock-specific bycatch mortality for the southern New England Atlantic herring fishery (2012-2013). Bycatch overall, but especially in the Atlantic herring fishery, was disproportionately assigned to the most severely depleted genetic stocks (alewife Southern New England stock – 70% of assignments; blueback herring Mid-Atlantic stock – 78% of assignments). These genetic stocks overlap in the region surrounding Long Island Sound, suggesting that bycatch taken from this area in recent years may be negatively impacting recovery efforts in this region. Our study suggests that mitigating bycatch on the southern New England fishing grounds may benefit recovery efforts for alewife and blueback herring genetic stocks that have experienced the greatest declines in spawning adult abundances.连接海洋与淡水生态系统的中营养级溯河洄游鱼类（anadromous fishes）的副渔获（bycatch）问题，正日益成为保育领域的重点关切。溯河型美洲西鲱（alewife, Alosa pseudoharengus）与蓝背西鲱（blueback herring, A. aestivalis）是沿海淡水与海洋食物网的重要组成部分，但其成体产卵种群的丰度已出现大幅下降。以淡水生境保育为导向的修复措施几乎未呈现一致的种群恢复迹象，这引发了学界担忧：西北大西洋商业渔业的副渔获可能抵消了前述保育行动的成效。本研究利用针对基线种群与副渔获样本的15个微卫星标记（microsatellites）基因分型数据，开展了遗传种群鉴定，以厘清副渔获在已明确的区域遗传种群间的分配格局。随后结合渔业观察员数据，对新英格兰南部大西洋鲱渔业（2012-2013年）的遗传种群特异性副渔获死亡率进行了估算。整体副渔获，尤其是大西洋鲱渔业的副渔获，显著偏向于受衰退最严重的遗传种群：美洲西鲱的新英格兰南部种群（占分配结果的70%）；蓝背西鲱的中大西洋种群（占分配结果的78%）。上述遗传种群在长岛湾周边海域存在分布重叠，这表明近年来该区域的副渔获或对当地种群恢复工作造成了负面影响。本研究显示，在新英格兰南部渔场减轻副渔获压力，或可助力种群衰退最为显著的美洲西鲱与蓝背西鲱遗传种群的恢复工作。