Linking scales of life-history variation with population structure in Atlantic cod

It is increasingly recognised that sustainable exploitation of marine fish requires the consideration of population diversity and associated productivity. This study used a combination of genotypic screening and phenotypic traits to define the scale of population structuring in Atlantic cod inhabiting the northern North Sea (ICES Sub-division 4a) and Scottish west coast (ICES Division 6a). The genetic analysis indicated an isolation by distance pattern with an even finer scale structuring than previously reported, that persisted over a decade and between feeding and spawning seasons. Spatial variation in phenotypic traits reflected genetic variation with cod maturing later and at a larger size near the Viking Bank in 4a. The identified population structuring provides an explanation for differences in historic changes in maturation schedules and the temperature exposure recorded in previous electronic tagging studies. The study also highlights how the mismatch between stock divisions and population units is leading to a misunderstanding about stock recovery.

学界日益达成共识：海洋鱼类的可持续开发需考量种群多样性及其关联的生产力水平。本研究结合基因型筛选与表型性状分析，明确了栖息于北海北部（国际海洋考察理事会（ICES）次级分区4a）与苏格兰西海岸（ICES第6a分区）的大西洋鳕鱼的种群结构尺度。遗传分析结果显示，种群呈现距离隔离模式，且其结构精细度较此前报道更高，该模式在十年间以及摄食与产卵季之间均持续存在。表型性状的空间变异与遗传变异相契合：在4a分区的维京浅滩附近，鳕鱼的成熟年龄更晚、体型更大。本次研究明确的种群结构，可解释此前电子标记研究中记录的鳕鱼成熟节律历史变化差异与温度暴露情况差异。本研究同时揭示了渔业种群管理分区与实际种群单元之间的错配，正导致对种群恢复情况的认知偏差。