Applied ichthyoparasitology: what can parasites tell us about fish stocks?

TIMI, J.T.

Buenos Aires

Congreso; 23rd. International Conference of the WAAVP; 2011

World Association for the Advancement of Veterinary Parasitology

The aim of veterinary parasitology is to know different kinds of parasites for proper diagnosis, treatment and control of diseases, an elusive goal in the marine realm where, with the exception of some aquaculture practices, the control of parasitic infections is unfeasible. On the other hand, and from a biological perspective, an ecosystem is considered as healthy if it is one that is rich in parasite species, and all information about their biology, diversity, life cycles etc., can be applicable for conservation purposes or sustainable development of resources under exploitation. One of the applied aspects of ichthyoparasitology is the use of parasites as biological markers to provide information on the stock discreteness of their fish hosts. An accurate identification of any exploited fish population, and the delineation of its boundaries with adjacent populations, is a prerequisite for the implementation of policies that ensure an efficient and sustainable management of the resources. In this sense, the use of parasites as biological tags has gained recognition as being applicable to the problems of fishery management and is increasingly being used worldwide, constituting a promissory tool to predict harvest locations and even to help combating illegal fisheries. Whereas several biological features of parasites (i.e. body size, lifespan and reproductive output) tend to produce similar population characteristics wherever the species become established, local environmental factors can regulate the survival and transmission success of infective stages, causing inter-population variations of parasite burdens. In other words, this methodology is based on the distribution patterns of parasites which, in the marine environment, are determined mainly by temperature–salinity profiles and by their association with specific masses of water. Analyses of distribution patterns of parasite species in relation to gradients in environmental (oceanographic) conditions in the South-west Atlantic showed that latitudinal gradients in parasite distribution are common in the region. These clines determine a differential composition of their communities at different latitudes, which makes possible the identification of different stocks of their fish hosts. Results of the successful use of biological tags for stock discrimination and fish migratory behaviour are shown, with emphasis on both geographic and across fish species distribution of anisakid nematodes; the most important group of parasites displaying zoonotic and economic implications in marine fisheries.