Growth and metabolic effects of stocking density in bullfrog tadpoles (Rana catesbeiana) under greenhouse conditions

Abstract

The density-dependents and physiological effects in bullfrog tadpoles (Rana catesbeiana Shaw, 1802) was evaluated to asses optimum stocking density. During 70 days, five treatments (1/4, 1/3, 1/2, 1 and 2 tadpole L -1) were evaluated under greenhouse conditions. Environmental variables, water quality parameters, biometric data, oxygen consumption and nitrogen excretion were measure every 3 weeks. At the end of experiment, the treatment of 1/4 tadpole L -1 obtained the highest weight, length and biomass. However, maximum survival (92.59%) and estimated final biomass (0.3051 g L -1) was found in the treatment of 1/3 tadpole L -1. Statistical differences were found in oxygen consumption (Kruskal-Wallis, H=19.935, P < 0.001). Average values of QO 2 ranging from 6.59 (2 tadpoles L -1) to 2.1 mg O 2 h -1 g -1 (1/4 tadpole L -1). Statistical differences were also found in ammonium excretion (H=17.089, P < 0.002), in which a maximum value of 0.366 mg NH 3 -N h -1 g -1 corresponded to the density of 1/2 tadpole L -1, and a minimum value of 0.122 mg NH 3 -N h -1 g -1 was observed in the density of 1/3 tadpole L -1. We suggest a stocking density of 1 tadpole per 3 L in order to minimize stress and optimize water.