Impact of the v-notch technical conservation measure on reproductive potential in a lobster (Homarus gammarus L.) fishery in Ireland

Abstract

In total, 7619 v-notched lobsters were released in the Wexford lobster fishery in Ireland between 1994 and 1999 in order to increase egg production. These lobsters were legally protected from fishing. Annual reproductive potential (RP) from these lobsters, based on numbers and size at release, was 2.6×107 eggs. Average ( 95% confidence limit) standing stock, between 1994 and 1999, from 31 Petersen population estimates was 29427 3871 female lobsters. Population RP was 6.9×107 eggs per year. After discounting numbers for natural mortality and incorporating increases in size of surviving lobsters, RP of v-notched lobsters in 1999 was 4.13×107 eggs per year. Catch rates of v-notched lobsters were correlated with numbers available for re-capture between 1994 and 1998. In 1999 catch rates were lower than expected, possibly because of repair and disappearance of the mark during moulting. Catch rates of undersized lobsters were 37% higher in 1998–99 than in 1994–97. In highly exploited small-scale lobster fisheries, substantial increases in RP can be achieved by v-notching. Demonstrating a dependency between local increases in RP and local recruitment is problematic and requires more information on the early life history and the recruitment process.