The bioenergetics of the southern catfish (Silurus meridionalis Chen): growth rate as a function of ration level, body weight, and temperature

Abstract

A feeding‐growth experiment was conducted in the laboratory on 114 young southern catfish (Silurus meridionalis Chen) with initial weights of 8.71–127.9g at 15, 20, 25 and 30°C. The experiment consisted of eight weight‐temperature groups, with five ration levels ranging from starvation to satiation in each group. A multiple regression equation fitted to the experimental data was developed to describe the relation between specific growth rate (SGR) and the three factors, ration level (RL), body weight (W) and temperature (T): SGR = 0.471 + 0.172lnW−0.0443T+0.0682Tln(RL + l). This predicts that with increasing temperature the specific growth rate decreases at lower ration levels and increases at higher ration levels. The equation, SGR =a+bln(RL + l), may be considered as the basic growth model where a is the maintenance metabolism exponent and b is the conversion exponent of the net energy; body weight and temperature influence the two parameters. With this relationship the two antagonistic effects of temperature on growth can be understood, increasing temperature imposes a negative effect on growth due to increment in energy cost for maintenance metabolism, and a positive effect due to higher efficiency of transforming food energy into net energy; the positive effect will increase at higher ration levels. This could also explain why at a restricted ration level relationships between growth and temperature are different in different species.