Parasites as biological tags for stock discrimination in marine fish from South American Atlantic waters

TIMI, JUAN T.

Glasgow, Escocia

Congreso; 11th International Congress on Parasitology,; 2006

World Federation for Parasitologists, British Society for Parasitology.

The use of parasites as biological tags in population studies of marine fish in the Southwestern Atlantic has been a successful tool to discriminate stocks for all species it was applied, namely: Scomber japonicus, Engraulis anchoita, Merluccuis hubbsi and Cynoscion guatucupa, the latter studied at a broader geographic scale, includinag samples from Uruguayan and Brazilian waters. The distribution patterns of marine parasites are determined mainly by temperature-salinity profiles and by their association with specific masses of water. Analyses of distribution patterns of some parasite species in relation to clines in environmental (oceanographic) conditions showed that latitudinal gradients in parasite distribution are common in the study area, and are probably directly related to water temperature. Indeed, temperature, which is a good predictor of latitudinal clines of richness and diversity of species, shows a latitudinal pattern in the Southwestern Atlantic coasts, decreasing southwards, due to the influence of subtropical and subantarctic marine currents flowing along the edge of the continental slope. This pattern also determines the distribution of zooplankton, whith a characteristic specific composition in different water masses. The cline in the distribution of parasites determines differential compositions of their communities at different latitudes, which makes possible the identification of the stocks of their fish hosts. Other features of the host-parasite systems contributing to the success of the parasitological method are: 1) parasites identified as adequate biological tags (i.e. anisakids) are widely distributed in the local fauna, 2) many of these species show low specificity and use paratenic hosts 3) structure of parasite communities are, in certain degree, predictable in time and space.