engleski

Prevalence of cymothoid isopod (Ceratothoa oestroides (Risso, 1816)) in fish farming of the Eastern Adriatic sea (Croatia)

Introduction: The cymothoid isopod Ceratothoa oestroides (Risso, 1816) is a protandric hermaphrodite fish parasite. It is a ubiquitous parasite with significant impact on fish health, usually found in Sparidae, Carangidae, Clupeidae, Maenidae, Scorpaenidea and Mugilidae families (Charfi-Cheikhrouha et al., 2000). Its common effects on fish in aquaculture can vary from growth retardation and decreased immunocompetency to mass mortalities of juvenile fishes, causing significant economic consequences in aquaculture (Mladineo, 2003). Most studies on this parasite in the Mediterranean aquaculture have described its influence on sea bass and sea bream (Horton and Okamura, 2001 ; Bouboulis et al., 2004). Last few years meagre (Argirosomus regius) has been introduced in fish farming in Croatia (Kružić et al., 2016). In this study, we examined C. oestroides infestation in the cultured meagre to provide new insights into importance and incidence of this parasite in this geographic area, and in order to improve existing fish farm management strategies. Methodology: Research was carried out at two commercial fish farms in the Central Adriatic, Croatia. First sampling and biometry of meagre was performed at the age of seven months (January 2016) and afterwards in February, March, April, May and July. A total of 2.028 fish were sampled. The incidence of parasites and weight and growth of meagre were monitored. Results: Parasites were found at both commercial fish farms. A total of 2.028 fish were examined and 84 (4.14%) of them were infested with parasites. The percentage of infestation was highest in February (7.0%) and lowest in May (2.4%). Biometric measurements revealed that meagre infested with the parasite had a significantly (P<0.05) lower weight and length compared with uninfested fish. Conclusions: Studies on infection of seabass and sea bream caused by C. oestroides in Croatia fish farms were reported earlier (Šarušić, 1999 ; Mladineo, 2003 ; Mladineo et al., 2009). The wild fish feeding around the cages, with wild bogue (Boops boops) as parasite carrier, was reported to be likely the source of the infection for aquaculture fish (Šarušić, 1999). In this study we determined that cultured meagre is also infested with C. oestroides with significant impact of this parasite on growth and weight of meagre in the offshore fish farming.

aquaculture, fish parasite, meagre

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