Spawning locations and larval dispersal of Atlantic Menhaden during 1977-2013

Atlantic Menhaden Brevoortia tyrannus exhibit particularly complex recruitment dynamics as a coastal-spawning species with seasonal migrations along the North American Coast from Nova Scotia, Canada, to Florida, United States. Despite a coast-wide reduction in juvenile production from the 1970s to the 1990s, Atlantic Menhaden continues to support one of the oldest and largest commercial fisheries on the US east coast. We used a stochastic partial differential equation model to estimate spawning location and larval dispersal on the Atlantic Coast over two time periods, with data from the Northeast Fisheries Science Center ichthyoplankton surveys conducted in 1977-1987 and 2000-2013. Within the study area, Atlantic Menhaden spawning appears to occur primarily near shore over a large spatial range, from southern New England to North Carolina over the majority of the year, but at greatest levels during November and December. Larger, older larvae were found over a similar spatial and temporal range, dispersing farther from shore. Between the two periods, we observed an increase in secondary, spring-time spawning events. We observed no major, directional spatial shift in spawning or dispersal. However, estimated spawning activity increased near Delaware Bay. Both small and large larvae were most abundant in the Southern portion of the study area during both periods. Yet, total spatial coverage of all larvae varied greatly among years until the mid-2000s, when the Atlantic Menhaden population was believed to have recovered reduction in juvenile production from the 1970s to the 1990s. In most recent years, we observed consistent and large areas of spawning and larval dispersal.