Stock structure and connectivity of the American lobster Homarus americanus in the southern Gulf of St. Lawrence: do benthic movements matter?

The long-range dispersal of pelagic larvae is often assumed to be the dominant force behind connectivity in the marine environment, with little consideration given to benthic movements. We analyzed data from an American lobster (Homarus americanus) tagging study (1980-1996) in the Gulf of St. Lawrence during which 37 579 adults from 14 locations were tagged and 6296 were recaptured after 1-6 years at large. The 10th percentile greatest distance moved by tagged lobsters after 1 year at large contributed to demographic connectivity between neighbouring statistical districts, fishing ports, and (in one location) management areas. Considering the incremental dispersal of lobsters after 2 versus 1 year at large, we estimated that the 10th percentile greatest benthic dispersal distances after 1, 2, and 5 years at large represented, respectively, 7%,14%, and 35% of larval dispersal in the "downstream" direction and 75%,111%, and 220% of larval dispersal in the "upstream" direction (similar results obtained based on mean dispersal values). We conclude that more attention should be given to benthic movements in estimating connectivity and stock structure in American lobster.