Size and age at onset of sexual maturity of female Norway lobster Nephrops norvegicus L. (Crustacea: Nephropidae) in the Strait of Sicily (Central Mediterranean Sea)

Abstract

The reproductive cycle of the Norway lobster (Nephrops norvegicus) female was investigated to determine the size and age at onset of sexual maturity (SOM), as a baseline to establish the minimum catchable size. Samples were gathered in four seasonal (Spring 1986 - Winter 1987) trawl surveys on the Italian side of the Strait of Sicily (Central Mediterranean Sea). The relative frequency of females in different stages of maturation and in berried conditions was observed. According to the ovary stages, gonadal maturation is attained during Spring and Summer; berried animals occur almost exclusively in Summer and Autumn, in about 40% of the sample. Length structure changes slightly by location and by season; recruitment to the gear occurs more or less continuously. Gaussian components appear to be highly overlapped; the resolution of the length frequency distribution values leads to the identification of multiple cohorts, five of which were well represented. The population attains 50% of maturity at 30-32 mm CL, corresponding to an age of 5 years. The mean size of the first Gaussian component from the catch (about 22 mm CL) is well below the estimated size at 50% maturity, suggesting a precocious recruitment to the fishery.