Effect of ambient temperature increase on intestinal mucosa amylolytic activity in freshwater fish

The relationship between the level of the intestinal mucosa amylolytic activity (AA) of juvenile goldfish Carassius auratus , carp Cyprinus carpio , roach Rutilus rutilus and perch Perca fluviatilis and the rate of water temperature increase was studied. Increase in water heating rate significantly influences AA and the level of upper lethal temperatures defined by critical thermal maximum (CTM) during different seasons. At a low rate of water temperature increase, 0.04 °C/h, AA and the level of CTM are maximal during all seasons. More rapid rates of heating, 4–50 °C/h, increase the AA during the summer and usually decrease it by 2- to 7.5-fold during other seasons. Rapid increase in ambient temperature in the autumn–winter period, unnatural for seasonal dynamics, produces a negative impact upon the fish’s carbohydrate hydrolysis rate and thermal resistance.