Pelagic to Benthic Coupling in Lobster (Homarus americanus) Recruitment

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Rates of larval settlement may be a major determinant of subsequent year-class size for many benthic invertebrates. Often it is difficult, however, to elucidate the relative importance of pre- and post-settlement processes to spatial and temporal variability in recruitment. The American lobster, Homarus americanus, recruits from a pelagic postlarva to shelter- providing benthic substrata, but little is understood about the regulating factors or the consequences of this process. We plan to study the linkage from late pelagic to early benthic phase along the central coast of Maine, where shallow subtidal cobble provides prime recruitment habitat. Our collaborative studies from 1989-1991 suggest that lobster recruitment at some sites may be limited by larval supply, whereas others may be limited by the availability of suitable habitat. We intend to use an experimental approach at two sites that consistently represent the extremes in recruitment density despite apparent similarities of their habitat. At these sites we will use habitat manipulations and postlarval seeding experiments to test the influence of postlarval supply, habitat quality, and density- dependent processes on benthic recruitment. Hydrographic data will be collected to examine possible differences in stratification as well as absolute temperature structure that may influence postlarval diving behavior.