Development of a Population Wide Index of Spawning Stock Biomass for Atlantic Mackerel

The northwest Atlantic Mackerel stock spawns in both U.S and Canadian waters. The U.S has declared the status of the unit stock as unknown, while a Canadian assessment of the stock’s northern contingent indicates biomass at a historic low. An Atlantic Mackerel abundance index derived from the Northeast Fisheries Science Center’s (NEFSC) spring bottom trawl survey, which was used in a recent U.S.-Canadian assessment, remains high, but is contradicted by other information about the status of the stock, prompting the need for an additional fisheries independent index. Here we describe the development of an egg index for U.S. waters. Ichthyoplankton were collected each year on the May-June NEFSC Ecosystem Monitoring survey. Fish eggs were sorted and identified to species. Atlantic Mackerel eggs were then developmentally staged. A northward shift in egg distribution has occurred over the past 15 years. Additionally, egg totals have decreased from thousands in the early 2000s to less than a hundred in recent years. We plan to develop a spawning stock biomass index using the egg production method. The new data series, when combined with ongoing Canadian egg abundance surveys, will provide the first range-wide abundance index for the entire northwest Atlantic stock.