Influence of settlement time and size on postsettlement growth in the American lobster (Homarus americanus)

We investigated the size and timing of settlement of postlarval (fourth ins tar) American lobster (Homarus americanus) and the size attained by the end of the first growing season. Mean size and duration of benthic instars (IV -XI) were obtained from a field growth experiment. Lobsters settling in ear ly- and mid-season were larger at each instar and had different growth prof iles than late-season settlers. In particular, the rate of growth at the fi fth and sixth instar transition was greater for early- and mid-season settl ers than for late-season settlers. Postlarvae settling early reached the ni nth instar sooner than mid- or late-season settlers. Estimates of size and intermolt duration of each instar for early- and late-season postlarvae wer e applied to planktonic postlarval data (1988-1995) to estimate growth traj ectories during the first year. For all years, postlarvae present early in the season were 30-50% larger (carapace length) and two or three instars fu rther developed than late settlers by the end of the growing season. Estima tes of size attained by the end of the 1994 growing season matched field-co llected benthic size frequency data for this same year. Although initial ca rapace length at settlement was important, the timing of settlement was mor e influential on the size attained by the end of the first growing season.