Coastal fish farming does not affect the total parasite communities of wild fish in SW Mediterranean

Abstract

The influence of sea-cage salmon farms in increasing the parasite loads of wild salmonids has received considerable attention due to the potential negative consequences for both natural populations and cultivated stock. However, studies dealing with the parasitological loads of reared fish of other species and their relation with farm-associated wild fish are scarce. In this work, cultured and aggregated, wild fish from 3 different fish farms and 2 control locations were compared by hook and line and spear-fishing. It was found that reared sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) did not share macroparasites with farm-associated wild fish (bogue Boops boops and Mediterranean horse mackerel Trachurus mediterraneus). Similarly, no effect of farms on the total parasite community was detected when it was compared farm-associated and not farm-associated wild bogue and mackerel neither a host-range enlargement that has been detected in some other works. Reduced numbers of cestodes, nematodes and the digenean Lecithocladium excisum (which is first recorded parasitizing T. mediterraneus) occurred in farm-associated wild fish compared to not farm-associated fish. In contrast, the digenean parasites Bacciger israelensis and Prodistomum polonii were favoured by the farm effect. Influence of farms on wild fish, such as diet modification, may be detrimental for some parasite species, while these same conditions could enhance others.