Microbial ecology of fish species ongrowing in Greek sea farms and their watery environment

Abstract

The present study focuses on the bacteriological profile of both watery ecosystem and fishes from different North and Central West Greek fish-farms ongrowing euryhaline fish species. The natural microflora of the fish and the water of their ongrowing units in selected farms were studied for a period of 20 months. The analyzed samples were mainly sea bream (Sparus aurata) 61.3% and sea bass (Dicentrarchus labrax) 24%. In most of the watery ecosystems coming from the different sampling areas, total and fecal coliforms as well as total and fecal streptococci were abundant in all water samples. Enterococcus, Escherichia coli and Pseudomonas were present at a level of 3 logs cfu/100 ml. The anaerobic Clostridium perfringens was found in vegetative (21.3%) and spore forms (13.3%). It is of interest to note that pathogens as Pasteurella piscicida and Vibrio anguillarum were isolated only in a small number of samples. Staphylococcus aureus was detected in 4% of the samples, other Staphylococcus sp. in 29.3%, E. coli in 30.7%, Salmonella sp. in 1.3%, Pseudomonas sp. in 13.3%, Clostridia lec(−) in 49.3%, Bacillus sp. in 38.7%, Vibrio sp. in 18.7%, Lactobacillus and Lactococcus sp. in 36% και 29.3% respectively. Vegetative forms of C. perfringens were detected in 22.7%. Although, our results showed no significant correlations between the sea water and fish microflora, more focus on this bipolar interacting system should be necessary in order to avoid any possible disturbance in the balance of the healthy farming ecosystem with the host organisms.