Effect of incubation water flow rate and egg population density on hatching success of Oreochromis karongae

Research was conducted to assess the combined effect of water flow rate and incubation egg population density on egg hatching period, hatchability, total mortality and fry survival of Oreochromis karongae. The treatments were (1) 0.09 l/sec and 125 eggs/l, (2) 0.09 l/sec and 417 eggs/l, (3) 0.17 l/sec and 125 eggs/l, and (4) 0.17 1/sec and417 eggs/l. There was a significant interaction effect whereby high flow rate (0.17L/sec) and low egg population density (125 eggs/l) resulted in the shortest hatching period of 4.61±0.07 days (p<0.05). There was no significant interaction effect between flow rate and egg population density on hatchability, total mortality, and fry survival (p>0.05). However, fry survival (74.56±9.48%) was higher at high incubation egg population density than at low incubation egg population density (24.37±37.79%) (p<0.05). The hatchiéng success is higher than reported in the past for Tilapias in Malawi. These results indicate that there is potential to increase O. karongae fry production by manipulating water flow rates and egg population density combinations during incubation.