Bacterial microflora associated with a coastal, marine fish-rearing unit

Populations of heterotrophic bacteria from a marine fish-rearing unit were estimated using a spread plate technique. Bacterial populations in winter were relatively low compared with counts in summer when the maximum water temperature was recorded. Almost 600 isolates were examined, and found mostly to be Gram-negative rods. The bacterial populations consisted of a diverse array of taxa, and the variations in total numbers were due to relative changes in the abundance of these. There were nine groups isolated exclusively from the surface of turbot, including Alcaligenes faecalis, Bacillus firmus, Photobacterium Angustum, P. logei, Pseudomonas fluorescens and unidentified Gram-negative rods. In addition, pure culture growth of Alteromonas haloplanktis and unidentified Gram-negative, budding bacteria were isolated from within the lesions of moribund turbot.