THE EFFECTS OF VARYING BROODSTOCK PAIRING RATIO IN INDUCED SPAWNING ON THE HATCHABILITY OF CATFISH Clarias gariepinus, Burchell, 1822 EGGS  

African sharptooth catfish, Clarias gariepinus is one of the most farmed fish species in West Africa, where commercial breeding is done using hormones including pituitary gland. This study was carry out using natural pituitary from male catfish for induced breeding of C. gariepinus under varying brood stock ratios. The broodstocks selected weighed between 800g and 1000g males, 900g and 1000g females. They were used for three induced breeding trials in treatment ratios of A (1 Male, M:1 Female, F), B (2M:1F) and C (1M:2F). Females under treatments A and B were injected with 2mls of the pituitary solution each, and C (1M:2F)  was injected with 1 pituitary (0.5 each ) of 1ml each. Fecundity of females in A was10500 eggs, B was 12600 and the two females of C were 9600 and 10200 eggs (added up to get 19800 eggs). The weight of eggs produced were A (1F, 35g), B (1F, 42g) and C (2F was 32 and 33g, mean= 33g).

Hatching started 24 hours after incubation and lasted for 33 hours. Percentage hatching for treatment A was 51%, B was 75% and C was 23%.The differences between the percentages showed that there was no significant difference p >0.05 between A(1M:1F) and B (2M:1F). Treatment C (1M:2F) showed no significant difference (p >0.05 ) as compared to treatment A(1M:1F). The percentage survival of the treatments indicated that C(1M:2F) was the highest 49.0% followed by A (1M:1F), 30% and B(2M:1F), 26%.There was no significant difference p >0.05 between A(1M:1F) and C(1M:2F) but treatment A(1M:1F) and B(2M:1F) showed significant difference (p <0.05). Treatment B with two males and one female broodstock had the highest number of stripped and fertilized eggs, hatchlings, low number of spoiled eggs and high survival rate. Fish farmers should use the broodstock ratio of 2 males to 1 female for induced spawning to help them get enough good seed for their fingerling production, and also use larger receptacles for higher hatchability.