Epidemiological and ecological effects of fishing on parasites of fished host species

Background/Question/Methods

Half of all species on the planet are parasites. Despite this ubiquity, we have only a rudimentary understanding of anthropogenic influences on parasite biodiversity. As one of the most disruptive and long-standing human impacts on the ocean, fishing may indirectly influence parasites by reducing the availability of parasite habitat and food resources (i.e., fish hosts). Here, we present the results of a study that addresses this hypothesis by assessing the burden of gill parasites of two exploited fishes (Cheilodactylus variegatus and Aplodactylus punctatus) collected from a series of marine reserves and matched open-access areas along the central Chilean coast.

Results/Conclusions

We did not detect significant differences in proportion of host individuals infected (prevalence) or the number of parasites per infected host (intensity) between protected and open-access areas, except for a single monogenean parasite species, which was both more prevalent and more intense in reserves than in open-access areas. But while we observed an epidemiological effect of fishing on only this single parasite, nearly all parasites responded to protection from fishing with an increase in their ecological abundance (i.e., abundance per unit area, rather than per host). These data therefore suggest that protection from fishing may facilitate fish parasite abundance and that the removal of fish from the world’s oceans over the course of hundreds of years could be driving long-term declines for some fish parasite populations.