ABSTRACT

Life histories and reproductive dynamics of the crayfish Orconectes virilis, the langoustine Nephrops andamanicus, and spiny lobsters of the genus Jasus are reviewed and compared. Fecundity per recruit values (the average number of eggs produced per female during a lifetime) were calculated to provide comparisons of mortality rates of larval and/or juvenile stages, both among the three lobster groups and between different populations of the same species. In relatively crowded populations of Nephrops density-dependent rates of growth and survival are reduced and sizes at maturity of females are small. Modeling of Jasus populations shows that fecundity per recruit is regulated by size at maturity of females, at both inter- and intraspecific levels. Egg size, phyllosoma larval size and puerulus size are correlated, and there are interspecific differences within the genus Jasus. Mean size at maturity is determined largely by average molt increments of juveniles, because the modal number of pre-puberty molts is not random but appears to be species-specific in these groups. Thus density-dependent growth of juveniles regulates size at maturity and egg production in these crustaceans, suggesting an indirect feed-back relationship between adult egg production and post-larval settling densities. Despite the apparent resilience afforded to lobster stocks by compensatory (density-dependent) mechanisms, overfishing is to be avoided-firstly because of the adverse economic impact, and also because reduced egg and larval production must diminish the capacity of a stock to resist environmental change.