Variations in the parasite fauna of the Patagonian toothfish (Dissostichus eleginoides Smitt, 1898), with length, season, and depth of habitat around the Falkland Islands.

The parasite fauna of Dissostichus eleginoides was examined from locations around the Falkland Islands. In total, of 11,362 individual parasites of 27 taxa were recovered from 105 fish. Two species, Ceratomyxa dissostichi and Sphaerospora dissostichi, represent new host records. The nematode Ascarophis nototheniae and the larval acanothocephalan Corynosoma bullosum were found to be new locality records and add to the knowledge of the biogeography and host specificity of parasites on the Patagonian Shelf. There were no significant differences in the mean abundance and prevalence of parasites recovered between sexes. Therefore, sex was not considered in further analysis and the data were pooled. Cysts of unknown etiology (CUE), the monogenean Neopavlovskioides georgianus, the larval acanthocephalan Corynosoma bullosum, and the digenean Neolepidapedon magnatestis had significant positive correlations with increasing host length. The larval Trypanorhynch cestode Grillotia erinaceus and the digenean Elytrophalloides oatesi showed significant negative correlations with increasing host length. CUEs, N. georgianus, the digenean Gonocerca physidis and E. oatesi showed statistically significant prevalence between summer, winter, and spring. The effect of depth on parasite communities was also examined, initially using a linear discriminant function analysis. The prevalence of individual parasites was then compared between depth strata using the chi-square test. The parasite communities on the shelf and deep water (> 1,000 m) were found to be different, whereas those caught at intermediate depths on the shelf slope were found to have parasite communities that were intermediate, containing a mixture of shelf and deeper-water parasites. The causes of the variations in parasite faunas in association with these intrinsic and extrinsic factors are discussed.