Effect of stocking density and age at stocking on growth and survival of Heterobranchus bidorsalis larvae

Abstract

Survival and growth performance of Heterobranchus bidorsalis larvae reared for 28 days at different stocking densities and ages were monitored to determine the optimum stocking density and age at stocking. Nine hundred fry were stocked at densities 100fry/m3 (SD1), 200fry/m3 (SD2), 300fry/m3 (SD3) and 400fry/m3 (SD4). Fry were stocked at day 3, day 6 and day 9 after hatching (A, B, and C respectively). They were fed with same commercial fry wean diet ad libitum. Growth indices (mean weight gain, mean total length, average daily growth rate, specific growth rate, performance index, condition factor) and survival rate were measured. The result showed that mean weight gain, mean total length, average daily growth and specific growth rate were stocking density dependent. Mean weight gain ranged from 0.09±0.03 in SD2A to 0.41±0.15g in SD1A. The least stocking density (100fry/m3) stocked at day three (SD1A) had the highest values of mean weight gain and mean length gain, while the highest survival was also recorded in the fish stocked at 100fry/m3 in day three (SD1A) and day nine (SD1C). The fish stocked in day three at 100fry/m3 had the highest performance index but the most consistent performance index was observed in fish stocked in day nine. It was concluded that H. bidorsalis fry should be stocked at 100fry/m3 at day three after hatching as this will enhance optimum survival and best yield.