Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, 20688, USA.
Fisheries and Oceans Canada, Institut Maurice-Lamontagne, Mont-Joli, QC, G5H 3Z4, Canada.
Sci Rep. 2021 Mar 23;11(1):6667. doi: 10.1038/s41598-021-86116-2.
The Atlantic mackerel (Scomber scombrus) in the Northwest Atlantic is comprised of northern and southern components that have distinct spawning sites off Canada (northern contingent) and the US (southern contingent), and seasonally overlap in US fished regions. Thus, assessment and management of this population can be sensitive to levels of mixing between contingents, which remain unknown. Multi-decadal trends in contingent mixing levels within the US fisheries region were assessed, and the contingent composition across seasons, locations, ages, and size classes were characterized using archived otoliths and developing a classification baseline based on juvenile otolith carbon and oxygen stable isotopes (δC/δO values). Classification of age ≥ 2 adults demonstrated that northern contingent mixing was prevalent within the US continental shelf waters during the past 2 decades (2000-2019), providing an important seasonal subsidy to the US winter fishery despite substantial depletion in spawning stock biomass of the dominant northern contingent. While the majority of older fish were of the northern contingent during the early 2000s, the southern contingent contribution increased with age/size class during the recent period (2013-2019). Spatial mixing was most prevalent during February and March when the northern contingent occurred as far south as the Delmarva Peninsula, but were mostly absent from US waters in May. A positive relationship (albeit not significant; r = 0.60, p = 0.07) occurred between northern contingent mixing and US fisheries landings, which could imply that higher contingent mixing levels might be associated with greater landings for the US winter mackerel fishery. The yield of the Northwest Atlantic mackerel depends upon the status of the northern contingent, with the southern contingent possibly more prone to depletion. Spatially explicit stock assessment models are recommended to conserve both productivity and stability in this two-component population.
北大西洋鲭（Scomber scombrus）在北大西洋由北部和南部两个组成部分组成，它们在加拿大（北部群体）和美国（南部群体）的产卵地不同，并且在季节性上在美国捕捞区域重叠。因此，对该种群的评估和管理可能对群体之间的混合程度敏感，而这种混合程度目前尚不清楚。评估了美国渔业区域内群体混合水平的多十年趋势，并使用存档的耳石和基于幼年耳石碳和氧稳定同位素（δC/δO 值）建立的分类基线来描述群体在季节、地点、年龄和大小类别的组成。对年龄≥2 的成年个体的分类表明，在过去的 20 年（2000-2019 年）中，北部群体的混合现象在美国大陆架水域中很普遍，尽管主导的北部群体的产卵stock 生物量大量减少，但仍为美国冬季渔业提供了重要的季节性补贴。尽管在 21 世纪初，大多数较老的鱼类都属于北部群体，但在最近的时期（2013-2019 年），随着年龄/大小类别的增加，南部群体的贡献也在增加。混合现象最普遍的时期是 2 月和 3 月，当时北部群体远至特拉华半岛，但 5 月时美国水域很少出现北部群体。北部群体混合与美国渔业捕捞量之间存在正相关关系（尽管不显著；r=0.60，p=0.07），这可能意味着更高的群体混合水平可能与美国冬季鲭鱼渔业的更大捕捞量有关。北大西洋鲭的产量取决于北部群体的状况，南部群体可能更容易枯竭。建议使用空间明确的种群评估模型来保护这两个组成部分的生产力和稳定性。
