Spatial and temporal variation in populations and community of ectoparasites on young snapper, Pagrus auratus (Bloch & Schneider) (Sparidae), from the wild and captivity at Port Hacking, Sydney, Australia

Abstract

Snapper in both the estuary (0+, 1+ age classes) and from offshore reefs (1+, 2+, 3+ age classes) at Port Hacking, NSW, were infested with the monogeneans Lamellodiscus pagrosomi, Anoplodiscus cirrusspiralis and Bivagina pagrosomi and the copepods Unicolax chrysophryerzus, Pseudoeucanthus australiensis, Hatschekia pagrosomi, Clavellopsis sargi and Lernanthropus atrox; offshore snapper also had the monogenean Choricotyle australiensis and the copepods Caligus spp. and Lepeophtheirus sekii. Most species had a higher prevalence, but not intensity, on offshore fish. Season was not a significant factor for most infrapopulations. Species richness, number of parasites and diversity were greater on offshore fish and differed among estuary samples but not offshore samples. Estuary infracommunities were dominated by L. pagrosomi (mainly 1+) and B. pagrosomi (mainly 0+); C. sargi and L. atrox dominated when richness was low. Offshore infracommunities were dominated by H. pagrosomi except in winter when L. pagrosomi was dominant, possibly owing to movement of estuary fish to offshore reefs. Captivity in experimental cages in the estuary resulted in transient increases in A. cirrusspiralis, B. pagrosomi and Benedenia sekii. Lamellodiscus pagrosomi increasingly dominated all samples and infracommunities. Neither condition factor nor stocking density had a significant influence on infestation.