Effect of density and sex ratio on gonad development and spawning in the crayfish Procambarus llamasi

Abstract

The effect of density and sex ratio on maturation and spawning in the crayfish Procambarus Ilamasi was evaluated during a 90-day study. Five stocking densities were tested: 10 org/m(2) (5 females/m(2)), 20 org/m(2) (15 females/m(2)), 34 org/m(2) (29 females/m(2)), 49 org/m(2) (44 females/m(2)) and 64 org/m(2) (59 females/m(2)), and five sex ratios (male/female) 1:1, 1:3, 1:6, 1:9 and 1:12. The Maturation Index (MI) results exhibited no significant differences between the high-density treatments, though there was a significant difference between these and the lowest density treatment. Females in the lowest density did not mature or spawn. The Gonadosomatic Index (GSI) showed no differences between densities, with high values in all treatments. Spawning increased in direct relation to density with the highest spawning percentage recorded in the highest density treatment. Density had a clear and significant effect on maturation and spawning in P. Ilamasi. (C) 2004 Elsevier B.V. All rights reserved.