Genomic outliers.

Lumpfish (Cyclopterus lumpus) is a transatlantic marine fish displaying large population sizes and a high potential for dispersal and gene-flow. These features are expected to result in weak population structure. Here, we investigated population genetic structure of lumpfish throughout its natural distribution in the North Atlantic using two approaches: I) 4,393 genome wide SNPs and 95 individuals from 10 locations, and II) 139 discriminatory SNPs and 1,669 individuals from 40 locations. Both approaches identified extensive population genetic structuring with a major split between the East and West Atlantic and a distinct Baltic Sea population, as well as further differentiation of lumpfish from the English Channel, Iceland, and Greenland. The discriminatory loci displayed ~2–5 times higher divergence than the genome wide approach, revealing further evidence of local population substructures. Lumpfish from Isfjorden in Svalbard were highly distinct but resembled most fish from Greenland. The Kattegat area in the Baltic transition zone, formed a previously undescribed distinct genetic group. Also, further subdivision was detected within North America, Iceland, West Greenland, Barents Sea, and Norway. Although lumpfish have considerable potential for dispersal and gene-flow, the observed high levels of population structuring throughout the Atlantic suggests that this species may have a natal homing behavior and local populations with adaptive differences. This fine-scale population structure calls for consideration when defining management units for exploitation of lumpfish stocks and in decisions related to sourcing and moving lumpfish for cleaner fish use in salmonid aquaculture.

圆鳍鱼（Cyclopterus lumpus）是一种跨大西洋分布的海洋鱼类，种群规模庞大且具备极强的扩散与基因交流潜力。这类特征通常被认为会导致较弱的种群遗传结构。本研究针对圆鳍鱼在北大西洋的自然分布全域，采用两种分析方法探究其种群遗传结构：其一，基于4393个全基因组单核苷酸多态性（Single Nucleotide Polymorphism, SNP）位点，对来自10个采样点的95尾个体进行分析；其二，基于139个鉴别性SNP位点，对来自40个采样点的1669尾个体进行分析。两种分析方法均检测到显著的种群遗传结构：大西洋东西部存在显著分化，波罗的海种群独具特色；英吉利海峡、冰岛及格陵兰海域的圆鳍鱼种群亦存在进一步分化。鉴别性SNP位点的分化水平约为全基因组SNP分析的2~5倍，进一步揭示了局部种群的亚结构特征。斯瓦尔巴群岛伊斯峡湾的圆鳍鱼种群分化程度极高，但与格陵兰海域的多数个体亲缘关系较近。波罗的海过渡带的卡特加特海域形成了此前未被报道的独特遗传类群。此外，研究还在北美、冰岛、西格陵兰、巴伦支海及挪威海域的种群中检测到进一步的亚分化现象。尽管圆鳍鱼具备较强的扩散与基因交流潜力，但大西洋全域观测到的高水平种群遗传结构表明，该物种可能存在出生地归巢行为，且其局部种群存在适应性分化。这种精细尺度的种群遗传结构，在制定圆鳍鱼种群开发管理单元以及鲑形目水产养殖中作为清洁鱼的圆鳍鱼采购与调运决策时，均需予以充分考量。