MULTIPLE INDUCED SPAWNINGS OF THE INDIAN CATFISH HETEROPNEUSTES-FOSSILIS (BLOCH) WITHIN A PROLONGED SPAWNING SEASON

Singhi, the Indian catfish Heteropneustes fossilis, attained gonadal m aturity repeatedly in a single spawning cycle by photothermal treatmen t. After the first spawning, maintenance at 30 C and 14 h light/10 h d ark for 3 wk induced recruitment of the next batch of mature oocytes f or subsequent spawnings. The number of eggs released declined with eac h spawning. However, fertilizability of the eggs was maintained until the fifth spawning. Mature fish were induced to spawn by D-Lys(6) salm on gonadotropin-releasing hormone agonist administration. The dose of salmon gonadotropin-releasing hormone agonist for the second and subse quent spawnings was determined to be 25-fold less compared to the dose administered for the first spawning. Fish released the maximum number of eggs upon induction when they were maintained continuously at 30 C and 14 h light/10 h dark for 6 wk. The result obtained in the present study points to a possibility of obtaining multiple spawnings from th ose species of farmed fish which spawn once a year.