Growth, Movement, Recapture Rate and Survival of Hatchery-Reared Lobsters (Homarus Gammarus (Linnaeus, 1758)) Released Into the Wild On the English East Coast

Abstract

From 1983 to 1988 over 49,000 three-month-old hatchery-reared lobsters were tagged with a microwire tag and released into the wild in Bridlington Bay on the east coast of England. The area supports a substantial fishery based on a large stock of naturally settled lobsters. Since 1988 approximately 57,000 lobsters have been tested at sea and at the landing place in order to recapture microtagged lobsters and assess their growth, movement, recapture rate and survival. Results to date show that microtagged lobsters have survived in the wild for up to eight years and have been caught in traps (or pots) by commercial fishermen. Lobsters began to reach the minimum legal size of 85 mm carapace length four to five years after release, but showed substantial individual variation in size at age. Most recaptures were recorded within six kilometres of known release sites, and showed strong site fidelity. Some recaptured females carried eggs. Data from additional T-bar tag-recapture experiments are used to estimate the exploitation rate generated by standard pots assuming either zero or a high rate of T-bar tag mortality and tag shedding. The exploitation rate is used to convert spot estimates of the catch rate of microtagged lobsters into estimates of their abundance for comparison with the number of lobsters released at individual sites. Corresponding estimates of survival from release to recapture average 84% and 50% for the two assumptions made about tag mortality and tag shedding in the T-bar tag-recapture experiment. It appears that juvenile hatchery-reared lobsters have survived well to recruitment and we offer this as a first quantitative assessment of pre-recruit survival for Homarus gammarus. The significance of this result for lobster stock enhancement and ecology is discussed.