Advection and settlement rates in a benthic invertebrate: recruitment to first benthic stage in Homarus americanus

Neustonic post-larvae of the American lobster (Homarus americanus) undertak e exploratory forays to search for and select bottom habitat for settlement . Assessments at the end of the settlement season at multiple sites have sh own that there may be about a 10-fold increase in concentration from the di spersed pelagic phase to the aggregated early benthic phase in lobsters. He re we examine recruitment at a single site over short time intervals (5-14d ) to evaluate the role of advection, estimate the proportion of potential s ettlers that recruited to the bottom, and evaluate whether time- or density -dependent effects influenced recruitment. We found that (1) tidal advectio n easily accounts for the average increased concentration from pelagic to b enthic stages; (2) recruitment ranged from 0.1% to 1.8% of the potential se ttlers advected over the site; (3) the proportion of post-larvae that recru ited was similar in high and low recruitment years and had a tendency to in crease late in the settlement season; and (4) recruitment was positively co rrelated with post-larval supply. Density-dependent effects may have existe d at the highest levels of recruitment. (C) 2000 International Council for the Exploration of the Sea.