Degree of Nematodes Worm Infection in Pelagic Fish Populations from the Romanian Black Sea waters

Abstract

Pelagic fish species can be affected by a series of infectious and parasitic diseases. The data used for this study are represented by the biological material collected between 2018 and 2019, from trap nets along the Romanian Black Sea waters. To establish the degree of parasitism, the following species of pelagic fish were studied: Sprattus spratus -sprat, Engraulis encrasicholus - anchovy and Trachurus mediterraneus- horse mackerel. Four species of endoparasites were identified, belonging to nematodes, as follows: Hysterothylacium aduncum, Contracaecum sp., Porrocaecumsp. and Anisakis sp. The parasites, especially found as larvae, more in free state and less trapped in the internal organs, infested the abdominal cavity, leading to degenerations, atrophies and reduction of the fish functions. The intensity of the parasitism infestation could be lethal, the size of the stocks being severely damaged. At the analysed fish species, the infestation degree was under 20 parasites per host, a low number of species recording the maximum value of 40 parasites per host. The parasites tend to accumulate with the increase of the fish's size, young stages being less affected.