engleski

Do captive conditions favor shedding of parasites in the reared Atlantic bluefin tuna (Thunnus thynnus)?

Since 2003, we have been monitoring parasite communities of Atlantic bluefin tuna that are caught from the wild and transferred into cages during spring-summer months, as well as assemblages in fish that exit rearing cycle during the winter harvest period, noticing their significant tend to decrease at the harvest time. Such phenomenon is rarely observed in rearing conditions since sea-farming is considered to amplify pathogen number by enabling multiple host-pathogen interactions. Increased host population densities as a hallmark of sea-cages aquaculture, have been reported to induce an increased virulence of microorganism, forming a suitable environment for the emergence, establishment and transmission of new pathogens. This can be further enhanced by the type of administered feed, as in captive tuna fresh baitfish has been suggested as paratenic or intermediate carrier of many parasitic helminthes. Unlike in most cultured fish species fed by manufactured feeds, such diet does not limit trophic transmission of parasites. In order to assess epizootiological behavior of tuna parasites assemblages at the beginning till the end of 1.5 year rearing cycle, we examined data on parasite prevalence and abundance over four years. The aim was to evaluate parasite diversity indices, composition and nestedness in respect to rearing moment.

Atlantic bluefin tuna; Thunnus thynnus; parasite communities; didymozoids

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