Data from: The origins of Atlantic salmon (Salmo salar L.) re-colonizing the River Mersey in northwest England

By the 1950s, pollution had extirpated Atlantic salmon in the river Mersey in northwest England. During the 1970s, an extensive restoration program began and in 2001, an adult salmon was caught ascending the river. Subsequently, a fish trap was installed and additional adults are now routinely sampled. In this study, we have genotyped 138 adults and one juvenile salmon at 14 microsatellite loci from across this time period (2001–2011). We have used assignment analysis with a recently compiled pan-European microsatellite baseline to identify their most probable region of origin. Fish entering the Mersey appear to originate from multiple sources, with the greatest proportion (45–60%, dependent on methodology) assigning to rivers in the geographical region just north of the Mersey, which includes Northwest England and the Solway Firth. Substantial numbers also appear to originate from rivers in western Scotland, and from rivers in Wales and Southwest England; nonetheless, the number of fish originating from proximal rivers to the west of the Mersey was lower than expected. Our results suggest that the majority of salmon sampled in the Mersey are straying in a southerly direction, in accordance with the predominantly clockwise gyre present in the eastern Irish Sea. Our findings highlight the complementary roles of improving water quality and in-river navigability in restoring salmon to a river and underlines further the potential benefits of restoration over stocking as a long-term solution to declining fish stocks.到20世纪50年代，污染导致英格兰西北部默西河(Mersey)中的大西洋鲑鱼(Atlantic salmon)彻底绝迹。20世纪70年代，一项大规模种群修复项目启动；2001年，研究人员捕获到一条溯河洄游的成年大西洋鲑鱼。研究人员此后布设了鱼类诱捕装置，如今会常规采集更多成年个体样本。本研究针对2001至2011年的样本，对138条成年大西洋鲑鱼与1条幼鲑进行了14个微卫星位点(microsatellite loci)的基因分型。 我们借助新近构建的泛欧洲微卫星基准(pan-European microsatellite baseline)开展种群归属分析(assignment analysis)，以确定这些个体最可能的起源区域。结果显示，进入默西河的鲑鱼似乎源自多个种群：依据分析方法的不同，占比最高（45%~60%）的个体被归属至默西河以北紧邻的地理区域内的河流，包括英格兰西北部与索尔威湾(Solway Firth)流域；另有相当数量的个体源自苏格兰西部、威尔士及英格兰西南部的河流。不过，源自默西河以西邻近河流的个体数量低于预期。 我们的研究结果表明，在默西河采样到的多数鲑鱼为向南洄游的迷路个体，这与爱尔兰海东部存在的主导性顺时针环流系统相符。本研究结果凸显了改善水质与提升河道通航能力在鲑鱼种群恢复中的协同作用，并进一步强调：针对鱼类种群衰退问题，作为长期解决方案，生境修复相较于人工放流具有潜在优势。