This research combines computer modeling and population genomics approaches to estimate sea scallop (Placopecten magellanicus) larval dispersal along the eastern Maine coast and to predict the source and sink populations of larvae. W e are modifying an individual-based hydrodynamic computer model of the coastal currents from the Bay of Fundy westward through the Gulf of Maine to include larval development and behaviors, such as growth and mortality rates, swimming speeds, and vertical migration patterns. These additions to the model will ensure that the larvae behave as active rather than passive particles.
Larvae are released from three sites, the Bay of Fundy, the eastern Gulf of Maine, and George’s Bank. Within each site, there are six adult beds. A similar model examined dispersal of blue mussel larvae in the same region and found that sites closer to the Bay of Fundy were more likely to house source populations, while sites to the west acted more as sink populations. Although scallop larvae may behave differently from blue mussels, our initial hypothesis is that the same coastal currents would disperse scallop larvae from eastern populations to western populations. In preliminary model runs, larvae from beds in the Bay of Fundy dispersed westward but did not reach the Gulf of Maine within the expected 30-40 day larval duration. Larvae from several of these beds appeared to get caught in eddies and be retained within the Bay of Fundy, preventing further westward transport. Thus, the Bay of Fundy populations may experience greater larval retention.
Model predictions will later be tested using genomic analyses and assignment tests to compare the degree of genetic similarity among predicted source sites and settlement sites. This will increase the number of scallop populations that have been genotyped, provide insight into the population connectivity and genetic diversity of Maine’s wild scallops, and allow for the identification of source populations that could be important in sustaining both the wild fishery and seed sources for scallop aquaculture.