Changes in the spawning distribution and biomass of atlantic mackerel (Scomber scombrus) in the Western atlantic ocean over 4 decades

Abstract

The Atlantic mackerel (Scomber scombrus) has a Wide distribution off North America that changes substantially seasonally and interannually, challenging attempts to track changes in stock size. We used egg collections to develop an index of spawning stock biomass for the southern contingent of Atlantic mackerel that spawns in U.S. Waters. These results Were combined With those from an egg survey of the northern contingent that spawns in the Gulf of St. lawrence, Canada, to develop the only available stockwide index. Egg production of Atlantic mackerel in the Western North Atlantic Ocean has dropped >90% from the 1980s to the 2010s. The contribution of the southern contingent has generally been around 5–10%, except for during the late 1970s and early 1980s When it Was 30–40%. On the continental shelf of the northeastern United States, there has been a northeastward shift in the distribution of eggs of Atlantic mackerel, With loW levels of egg production recently at the historically important spawning location off southern New England. Overall, the index of spawning stock biomass generated from surveys in the Waters of the United States and Canada provides a much needed means of tracking fluctuations in the biomass of this commercially valuable migratory species.