Effect of different temperature regimes on metabolic and blood parameters of silver catfish Rhamdia quelen

The silver catfish (Rhamdia quelen) is a teleost native to South America. It can resist cold winters and grow quickly in the summer and is an important species for aquaculture in both temperate and subtropical climates. The effect of different water temperatures (15, 23 and 31 degreesC) on hematological and metabolic parameters in blood, liver and white muscle was investigated in this species following chronic (21 days) and acute (12 h) exposure. In both experiments, hematocrit, hemoglobin and cortisol were unchanged, but plasma glucose levels increased at a temperature of 31 degreesC and decreased at 15 degreesC, when compared to control. Fatty acid levels decreased at 31 degreesC, and triacylglycerol levels increased at 15 degreesC in the 21-day experiment compared to control. One of the most interesting results of this study was the decrease of total protein in the liver and white muscle of fish exposed to 31 degreesC for 21 days. Following 21 days, liver glycogen levels decreased at 15 and 31 degreesC and glucose and lactate contents increased at 31 degreesC compared to control. In white muscle, glycogen and glucose levels increased at 15 and 31 degreesC, while lactate decreased at 31 degreesC. No alterations were observed in the liver or white muscle of fish exposed to the different temperature for 12 h. Taken together, these results suggest that temperature and time of exposure influence metabolic parameters in the plasma, liver and white muscle of silver catfish. (C) 2004 Elsevier B.V. All rights reserved.