METAZOAN PARASITE COMMUNITY STRUCTURE IN BROWN TROUT FROM 2 LAKES IN WESTERN IRELAND

A total of 549 brown trout were caught from two lakes, Lough Feeagh an d Bunaveela Lake, in the Burrishoole system, Co. Mayo, Ireland. Seven species of metazoan parasite were detected but only four species occur red in greater than or equal to 10% of the sample. The parasite commun ity of the trout was dominated by a single species, Pomphorhynchus lae vis, with a prevalence of 58%. Only one allogenic helminth species was recorded from the trout, Diphyllobothrium ditremum, with the communit y mainly comprising autogenic species. Few differences were found betw een 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 helm inth community with little potential for interspecific interactions. H ost age was found to significantly influence these indices of infracom munity structure.