POPULATION-DYNAMICS OF THE MONOGENEAN ANOPLODISCUS-CIRRUSSPIRALIS ON THE SNAPPER, PAGRUS-AURATUS

Populations of Anoplodiscus cirrusspiralis were monitored for 1 year o n tagged individual snapper in experimental cages kept in a large on-s hore pond with flow-through filtered sea water. The cages were stocked with small and large fish at either low or high initial density. Irre spective of size and density, snapper with light initial infections ma intained light infections, whereas fish with heavy initial infections showed fluctuations in parasite population size throughout the year. T hese data indicate that some snapper have an innate resistance to infe ction by A. cirrusspiralis, with little evidence for acquired immunity induced by heavy infection. Parasite longevity was greater on the pec toral fin than caudal fin, and greater on large than small fish irresp ective of fish density; longevity was greater on susceptible fish than on resistant fish. Recruitment and mortality rates were greater on th e pectoral fin and in low density cages, but were not influenced by fo rk length. (C) 1998 Australian Society for Parasitology. Published by Elsevier Science Ltd.