Evaluation of Spawning Induction of African Catfish
(Clarias gariepinus)by Heteroplastic Hypophysation

 

Author(s): Sileshi Gadissa and L. Prabha Devi

Abstract: The study was conducted at Ziway Fisheries Resource Research Center situated 160 km south of Addis Ababa in the mid rift valley of Ethiopia. In the present experiment, specimens of Clarias gariepinus  both male and female fishes  having body weight  in the range of 0.5-2.0 kg were collected from Lake Ziway  and stocked in  concrete ponds having size of 7x5x1m provided with a water flow and replacement system.  The brood stocks were fed with pellet feed prepared from Noug cake and wheat bran (2:1) at 3 % of their   body weight. The whole pituitary glands were removed from the donor fishes (Cat fish, Carp, and Nile tilapia) and preserved in absolute alcohol (97 %). Pituitary glands were homogenized in a tissue grinder (mortar and pestle) with 2ml physiological salt solution (9 gm salt in 1 lit of water) and refrigerated until use. After conditioning for a period of fishes of average weight 1kg were selected for injection. The pituitary solution was drawn and gravid females were injected intramuscularly at the dose of 3 mg/kg body weight. The fishes were then kept in spawning tanks and removed after 13.5 h of latency period to check the condition.  The fully ripened females were stripped to collect the eggs in a shallow bowl and fertilized with milt collected from the male. Wet fertilization was performed with saline solution and water. The fertilized eggs were incubated at 23oC. While incubating the egg samples were drawn and the rate of fertilization was determined. Hatching occurred within 33hrs and hatchability rate (%) was determined by counting the active hatchlings. Those fishes injected with catfish and carp pituitary extract resulted in 76.93% and 80.53% fertility rate, and 45.30% and 42.93% hatchability rate respectively. The average spawning fecundity for fishes treated with catfish and carp pituitary extract were 6993 and 54633 respectively.  However, the same dose of Nile Tilapia pituitary extract gave no spawning response.   Even though the results on the fertility rate and hatchability were not statistically significant (P>0.05), catfish pituitary extract was equally potent and effective as that of carp pituitary extract to the recipient female catfish.

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