Use of Human Chorionic Gonadotrophin (hCG) for Induced Spawning in Tilapia Under Laboratory Conditions

Abstract

A study was conducted to determine the optimum dosage of Chorulon®, a commercial preparation of human chorionic gonadotrophin (hCG), for increasing spawning rates in the Nile tilapia, Oreochromis niloticus, under laboratory conditions. Dosages of 500-3,500 IU·kg·1 body weight hCG were injected intramuscularly into sexually-mature females reared in fiberglass aquaria. Spermiating males were provided at 1 :1 sex ratio. The number of ovulated and mouthbrooding females were determined 24 h after injection. The eggs from ovulated females were stripped and fertilized artificially while those from mouthbrooding females were removed from the oral cavity of the fish. All eggs were transferred to individual zuger jars for determination of pigmentation rates as an indicator of fertilization rates. Results showed that dosages of 2,000-3,500 tu·kg·1 hCG were effective in significantly increasing the percentage of females either ovulating or mouthbrooding 24 h after injection (25-75%), with pigmentation rates ranging from 36 to 83%. The optimum dosage of the hormone was 3,500 IU·kg