Constructing a Larval Index for Atlantic Mackerel on the Northeast U.S. Continental Shelf

Atlantic Mackerel (Scomber scombrus) are a common forage fish species in the northwest Atlantic and prey item for large predatory fish, marine mammals and seabirds. Recent low catches of the Northeast U.S. Atlantic Mackerel stock have motivated further research to better understand the species’ life history and historical population trends. One of the immediate interests involves constructing annual larval indices for the population to provide an additional estimate of spawning stock biomass and to determine the importance of larval abundance on the variability in annual recruitment. To aid this effort, we constructed an annual larval abundance index for the U.S. contingent of the northwest Atlantic stock. Mackerel larvae abundance-at-length data were analyzed from several multiyear plankton sampling programs, including NOAA’s Ecosystem Monitoring (EcoMon) Program. Larval index calculations incorporated larval growth, mortality and hatching seasonality models to standardize abundances to an equivalent daily age. Preliminary results indicate that there is large interannual variability in the larvae population over the last decade. The larval index will be analyzed with environmental indices to understand oceanographic influence on larval prevalence. Additionally, larval indices will be compared to annual recruitment levels to estimate the variability of year class strength associated with larval survival.