The presence and localization of acid and alkaline phosphatase, non-specific proteases, aminopeptidase, amylase. non-specific esterase and lipase was investigated by histoenzymologic methods in fed and fasting turbot from day I to day 40 post-hatching and compared with published data. Alkaline phosphatase and aminopeptidase activities were detected at day I in the distal region of the developing digestive tube. At day 3 (opening of the mouth) aminopeptidase and alkaline phosphatase activities were found all along the intestine. Sites of non-specific esterase and protease activities became apparent in the digestive tract at days 2 and 3 respectively.Amylase was present in the exocrine pancreas at day 3 and in the lumen of the intestine at day 4. Acid phosphatase was active in the cellular structure surrounding the yolk stores and in the lipid droplets at day I and in the intestinal epithelium at day 3. Lipase was found at day 15 when the larvae metamorphose into juveniles.All the investigated enzymes were detected in fasting animals, except for lipase. However, the intensities of the enzymatic activities were weaker in the fasting specimens relative to the fed specimens between days 7 and 10.

Rainbow trout were inoculated with Aeromonus salmonicida (AS) and 24 h later the tanks were drained off and the trout were kept for 30 min in 3 cm of water on the bottom of the tanks. This manipulation was considered as handling and anoxic stress. Twenty four hours later the stressed fish showed a leucopenia, mainly a lymphopenia. The chemiluminescence (CL) response of the head kidney phagocytes was lower in stressed fish. The inoculated-unstressed fish showed a greater CL response than the controls (non inoculated-unstressed). The mortality rate after AS inoculation was greater in the stressed than in the unstressed fish. When the stress was repeated four times for 15 min during 2 days, the CL response was lower; no difference was observed when the fish were stressed eight times for 15 min over 4 days.

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