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 instar) 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 early- and mid-season were larger at each instar and had different growth profiles than late-season settlers. In particular, the rate of growth at the fifth and sixth instar transition was greater for early- and mid-season settlers than for late-season settlers. Postlarvae settling early reached the ninth instar sooner than mid- or late-season settlers. Estimates of size and intermolt duration of each instar for early- and late-season postlarvae were applied to planktonic postlarval data (1988-1995) to estimate growth trajectories during the first year. For all years, postlarvae present early in the season were 30-50% larger (carapace length) and two or three instars further developed than late settlers by the end of the growing season. Estimates of size attained by the end of the 1994 growing season matched field-collected benthic size frequency data for this same year. Although initial carapace length at settlement was important, the timing of settlement was more influential on the size attained by the end of the first growing season