Assessing the impact of habitat and stock enhancement for the American lobster (Homarus americanus), in Narragansett Bay, Rhode Island

Habitat enhancement and stock enhancement methods were examined as to their effect on abundance of the lobster, Homarus americanus, in Dutch Harbor in Narragansett Bay, Rhode Island. Six experimental artificial reefs for lobster were established in Dutch Harbor in February 1997. The reefs were constructed identically consisting of two portions made up of cobble and boulders. The area was monitored for 6 months before placement and five years after placement using a combination of visual surveys by SCUBA divers, trap sampling, a tag-recapture program and airlift sampling for young of the year. Two areas were used as comparison sites, a soft bottom habitat adjacent to the reefs and a rocky habitat 1 km away at Dutch Island. Juvenile and adult lobster density at the reef sites increased from near zero to greater than one lobster per m2, significantly higher than the two comparison areas. An approximate population size of 1250 lobsters for the reef sites was calculated from the tag-recapture and visual survey information. There was a significant increase over the pre-reef condition in the number of naturally settling young of the year at the reef sites. In addition, during three of the years, 3 reefs and 3 natural areas were seeded with micro-wire tagged hatchery-reared 5th stage lobsters. Only three out of 6000 released tagged lobsters were recovered, and there was no significant difference in density of young of the year between seeded and unseeded areas. Possible behavioral deficiencies in 4th and 5th stage hatchery-reared lobsters were examined using time budget analysis and predator trials. Hatchery-reared 4th stage lobsters were found to behave differently than wild-caught lobsters and differences existed between hatchery-reared lobsters from different sources. The addition of habitat did significantly increase the numbers of lobsters in Dutch Harbor through increased settlement and migration. The addition of hatchery-reared lobsters did not contribute to enhancement at the reef sites. This could a result of the abnormal behavior displayed by the hatchery-reared lobsters that could have led to increased rates of predation once released into the natural environment