Metazoan parasite community structure in brown trout from two lakes in western Ireland.

A total of 549 brown trout were caught from two lakes, Lough Feeagh and Bunaveela Lake, in the Burrishoole system, Co. Mayo, Ireland. Seven species of metazoan parasite were detected but only four species occurred in > or = 10% of the sample. The parasite community of the trout was dominated by a single species, Pomphorhynchus laevis, with a prevalence if 58%. Only one allogenic helminth species was recorded from the trout, Diphyllobothrium ditremum, with the community mainly comprising autogenic species. Few differences were found between the two lakes, although the larger lake, Lough Feeagh, did contain some trout which harboured more parasite species and had, on average, fish with higher numbers of individual parasites. Measures of species richness and diversity were very low, indicating an impoverished helminth community with little potential for interspecific interactions. Host age was found to significantly influence these indices of infracommunity structure.