Bacterial strains isolated from the kidney and liver of grey mullets, Mugil platanus Giinther, 1880, captured in Cananéia, São Paulo State, Brazil, in October 1996, belong to the genera Micrococcus, Pseudomonas, Flavobacterium, Aeromonas and Vibrio. The resistance/susceptibility patterns of the isolated micro-organisms to nine antimicrobial substances were determined, the more resistant bacteria had been Pseudomonas, Flavobacterium and Micrococcus. To the best of the authors knowledge this is the first bacteriological study done on Mugil platanus in Brazil.

Mullets, Mugilplalanus Günther, 1880. were obtained from the estua-rine area of CananÉia (São Paulo, Brazil) and from freshwater tearing tanks. For each fish the body weight, body length, gonad weight and gonad maturation stage were recorded and the allometric index (K) was calculated. Blood was collected for hematocrit (Ht), hemoglobin level (lib), total cell count (Er), and the determination of hematological indices (MCV. MCH, MCHC), as well as the differential leukocyte count (lymphocytes, monocytes, neutrophils, basophils and '"other cells"). The averages of the hematological analyses, hematological indeces, condition factor and leukocytes percentage of the specimens acclimated to fresh water were significantly higher than those of the specimens from the estuary.