Maturity, fecundity and reproductive potential of the European lobster (Homarus gammarus) in Ireland

Fecundity and size at maturity of the European lobster Homarus gammarus (Crustacea: Decapoda) was estimated in four coastal regions of Ireland. Egg size increased with carapace length (CL) (egg size = 0.9939 x 1n (CL)-3.0809). The size-fecundity relationship for all coasts combined was (fecundity=0.0044 x CL3.1554). Physiological maturity was assessed using ovary colour, ovary factor, ova size, abdomen width/CL ratio, cement gland activity and moult status as criteria. Size at 50% maturity varied from 92.5 to 96 mm depending on region. The size-maturity relationship for all coasts combined was (Maturity-1/(1+exp(14.595-0.15598xCL))). Over 60% of lobsters in the commercial landings were under the size of 50% maturity. Relative reproductive potential (RRP) of different size-classes was calculated from the size-fecundity and size-maturity models and the numbers by length in the landings. the modal RRP size-class wa 98-100 mm. The commercial landings were dominated by the 86-92 mm size-classes.