Comparison of methods for sampling ectoparasites from coral reef fishes

Methods for sampling ectoparasite assemblages were compared using 7 species of coral reef fishes (Acanthochromis polyacanthus, Thalassoma lunare, Ctenochaetus striatus, Chlorurus sordidus, Scolopsis bilineatus, Hemigymnus melapterus, and Siganus doliatus). Estimates of total numbers and composition of ectoparasites were dependent on post-collection handling techniques and the method of ectoparasite removal. Fish were enclosed within plastic bags under water at the point of capture. Filtration of water from the plastic bags revealed a large number of parasites (mainly gnathiid isopods) that had detached from the host on capture. A subsequent sea-water rinse removed a large number of ectoparasites, but further treatment with the anaesthetic chloretone released additional individuals. The few remaining parasites were removed by visual inspection. A chloretone bath was more effective than a sea-water bath at removing parasites. The species composition of parasites recovered by a chloretone bath plus a visual survey was different from that recovered with a sea-water bath and visual survey; this suggests that traditional scanning techniques may not detect all parasites.