Early life history and recruitment processes of clawed lobsters

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This review focuses on the larval, postlarval, and early benthic life of Homarus and Nephrops, the two best studied, and commercially most important, genera of the Nephropidae. Processes acting during this time of the life cycle may be critical of the fate of a cohort. In the past decade, significant advances have been made in understanding events before and after settlement. Nephrops and Homarus are very similar with respect to the processes affecting the distribution of the pelagic larvae and postlarvae: wind, currents and larval behavior play a significant role. Duration of the pelagic phase is determined by temperature, timing of settlement, and perhaps nutrition. Both genera probably arc quite selective of substratum during settlement, but this has been investigated only in Homarus, where substratum type, odor, and predator presence affect choice of habitat. The two genera contrast, however, with respect to some of the processes occurring during and after postlarval settlement. Although both are cryptic, newly settled Homarus are found in shallow, rocky habitats, while settled Nephrops arc found in deep water, in burrows they construct in cohesivc mud. Homarus undergoes a developmental change in behavior within the first few years of benthic life that causes an increasingly wide range of movement; sexually mature H. americanus can move hundreds of kilometers in a year. Nephrops emerges more as it grows, but appears to be far more sedentary than Homarus. Thus in contrast to Homarus, a number of distinct populations of Nephrops exist within the species range that are clearly defined by habitat boundaries. New techniques now permit routine census and tagging of early benthic phase Homcarus, making it possible to follow year classes from the time of settlement. It is the years immediately after settlement that a cohort may be subject to density-dependent controls, a key issue facing workers on both groups.

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