Multiple induced spawnings of the Indian catfish Heteropneustes fossilis (Bloch) within a prolonged spawning Season

Abstract

Singhi, the Indian catfish Heteropneustes fossilis, attained gonadal maturity repeatedly in a single spawning cycle by photothermal treatment. After the first spawning, maintenance at 30 C and 14 h light/10 h dark for 3 wk induced recruitment of the next batch of mature oocytes for subsequent spawnings. The number of eggs released declined with each spawning. However, fertilizability of the eggs was maintained until the fifth spawning. Mature fish were induced to spawn by D-Lys⁶ salmon gonadotropin-releasing hormone agonist administration. The dose of salmon gonadotropin-releasing hormone agonist for the second and subsequent 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 those species of farmed fish which spawn once a year.