Habitat restrictions in early benthic life: experiments on habitat selection and in situ predation with the American lobster

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In shallow marine environments, many animals that eventually attain large body size and range widely are restricted to refugia early in life. A prime example is the American lobster Homarus americanus Milne Edwards. During the first few years of benthic life, lobsters are most strongly associated with shelter providing habitats (e.g., cobble) but this association is less frequent as they grow. The restricted distribution of such early benthic phase lobsters (5- ≈ 40 mm carapace length, CL) may be reinforced by predation, but experiments to quantify predators and predation rates in situ have not been reported. This study confirms previous habitat selection studies in showing that shelter-seeking behavior is likely the proximate cause of the association, but that predation probably reinforces the association until lobsters outgrow their most vulnerable size. Field predation experiments and video observation show that tethered early benthic phase lobsters were attacked by demersal fishes and crabs significantly more often when unsheltered by cobble, and that this vulnerability declines dramatically with increasing body size. Moreover, many of the species of fish and crab predators observed by video were common at the five sites censused in mid-coast Maine, and occur throughout the range of the American lobster. There is strong evidence that lobsters and their macruran (large abdomened) allies in shallow marine and aquatic environments are similarly restricted to shelter-providing habitats early in their benthic life, possibly because of their inability to avoid predators by rapidly burying themselves in sediment.