THE SUPRAPOPULATION DYNAMICS OF LERNAEOCERA-BRANCHIALIS AND LERNAEOCERA-LUSCI IN THE OOSTERSCHELDE - SEASONAL ABUNDANCE ON 3 DEFINITIVE HOST SPECIES

Quantitative samples of the demersal fish fauna of the Oosterschelde w ere taken between May 1988 and July 1989, The instantaneous mortality rates of the 1988 year classes of whiting (Merlangius merlangus L.), s and goby (Pomatoschistus minutus Pallas) and bib (Trisopterus luscus L .) were estimated at 0.017 d(-1), 0.014 d(-1) and 0.018 d(-1), respect ively. These three species were examined for the presence of mesoparas itic pennellid copepods. Combination of host population densities and parasite infection intensities allowed for estimation of parasite popu lation density Whiting were infected with Lernaeocera branchialis shor tly after their arrival (April-May) in the Oosterschelde. By the end o f the year approximately 80% of the first year class whiting were infe cted. Spawning sand gobies were infected with Lernaeocera lusci in May and June. Though the prevalence of L. lusci on juvenile sand gobies i n autumn was low, the parasite population density in this period was h igh. First year class bib were mainly infected by L. lusci after their transition from a pelagic to a demersal behaviour in August. It is su ggested that L. branchialis has one generation each year, whereas L. l usci has two. A biological model of the life cycle of both parasite sp ecies is presented. (C) 1997 International Council for the Exploration of the Sea.