Spawning performance and seed production from hybridization between Oreochromis spilurus and the GIFT strain of the Nile tilapia Oreochromis niloticus

This study compared the spawning performance of four crosses between the salt-tolerant tilapia Oreochromis spilurus and the fast-growing genetically improved farmed tilapia (GIFT) strain of the Nile tilapia Oreochromis niloticus: (1) O. spilurus , ♀ × O. spilurus ♂ (SS); (2) Nile ♀ × Nile ♂ (NN); (3) Nile ♀ × O. spilurus ♂ (NS) and (4) O. spilurus ♀ × Nile ♂ (SN). In each cross, males and females having mean weights of 157 and 115 g, respectively were stocked in 0.43m³ tanks at a male to female ratio of 1:3. Seeds (unhatched eggs, yolk-sac fry and free swimming fry) were harvested biweekly for 127 days. Viable spawns resulted from all crosses. The NN cross produced the highest total seeds tank^-1 (2890), seeds (kg female)^-1day^-1 (48.3), seeds m^-2 day^-1 (23.3) and seeds female^-1 day^-1 (7.9), followed by the SS and SN crosses. The NS cross had the lowest fecundity. Lower spawning parameters in the NS and SN crosses may be attributed to the lower social compatibility between the males and females compared with that of the pure parents. The survival and growth of the offspring from the four crosses will be compared in seawater (37-40 g L^-1) to assess whether hybrid vigor was produced.