engleski

THE CULTURE OF ATLANTIC BLUEFIN TUNA (Thunnus thynnus): DETERMINATION OF SPOILAGE BACTERIA

Tuna farming is a significant part of the aquaculture production. Croatia is one of the main capture-based Atlantic bluefin tuna aquaculture producers in Mediterranean. Despite the large number of studies about aquaculture, very little information is available about tuna aquaculture monitoring, especially about fish health management. The most useful approach in fish health management is prevention of disease and monitoring of the microorganisms. There is a shortage of information available for cultured tuna, particularly for Atlantic bluefin tuna (Thunnus thynnus). Generally, main data described parasitofauna and parasitic diseases, while the data on bacteria are sporadic. Available data describe presence of bacteria only in the context of pathological conditions and disease outbreaks in tuna. Appearance of disease in humans as a result of poisoning by eating unsuitable tuna meat is better described, especially with histamine producing bacteria. The aim of this research was to determine the spoilage bacteria of Atlantic bluefin tuna aquacultured in the Adriatic Sea. Sampling was conducted on Atlantic bluefin tuna farm in the area of central Adriatic. Samples were taken from 10 randomly sampled Atlantic bluefin tuna in spring and autumn period, from 2003 to 2008. Samples for bacterial analyses were collected from skin and gills swabs using sterile cotton stick (Eurotubo, Spain), as well as from spleen, liver and kidney using sterile bacterial loop. All samples were cultured on DifcoTM Tryptic Soy Agar (BD, USA) supplemented with 1 % NaCl and on the DifcoTM TCBS Agar (BD, USA). Isolated strains were characterized using the API kits (bio Mérieux, France) and identified by the APILAB Plus identification software (bio Mérieux, France), whereas identification of isolated Vibrio strains was carried out by PCR and sequencing. Bacteria of Atlantic bluefin tuna were mostly Gram-negative, with low number of Gram-positive bacteria. This research recorded the presence of spoilage bacteria in the examined Atlantic bluefin tuna from genera Pseudomonas, Moraxella and Vibrio. Klebsiella pneumoniae, one of the histamine fish poisoning bacteria in humans, was detected as a part of bacterial community of Atlantic bluefin tuna.

Adriatic Sea; Atlantic bluefin tuna; spoilage bacteria; Pseudomonas; Moraxella; Vibrio alginolyticus; Klebsiella pneumoniae

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