Production of Nephrops norvegicus larvae in the Irish Sea

Abstract

 Plankton survey data from 1982, 1985 and 1995 were used to estimate the annual production of Nephrops norvegicus (L.) larvae in the Irish Sea. The larval abundance data from each set of surveys were analysed using the same temperature-to-stage-duration relationships. The production of larvae was similar in all 3 yr at approx. 360 × 10⁹ Stage I larvae per year. The estimated production in the eastern Irish Sea was 5% of the value for the western Irish Sea. This corresponded well to the sizes of the fisheries and the relative areas of the mud patches. Larvae in both areas were found to hatch over 5½ wk, centred on the first week in May. The time lag between onset of production of each stage reflected the estimated stage durations, but the lag between maximum production of each stage was much shorter than expected.