Contact with Males is not Necessary for Natural Spawning of Tilapia Females, and Natural Spawns of Isolated Females Remain Viable for Controlled Artificial Reproduction.

Abstract

Blue tilapia Oreochromis aureus (Steindachner) females isolated in glass tanks from visual, olfactory or behavioural contact with males spawned spontaneously, indicating that females do not require cues from males to spawn naturally. Inter-spawning interval of isolated females in contact (17.0 days) and out of contact (17.3 days) with males was shorter (P<0.05) than that of communal females (19.9 days) in contact with males in the same tank. The significantly longer inter-spawning interval of the communal females may be related to greater fish density or spawning interruptions from intra- and inter-sexual aggression. Egg clutches removed from the mouths of incubating tilapia females in isolation were successfully fertilized and hatched artificially. Egg viability decreased rapidly after 20 min of hydration to very low levels until hatching was not possible 40 min. after contact with water. Further studies are necessary to compare larval survival of natural spawns of
isolated females and stripped eggs, since ultimate fry output depends on this parameter.

Journal of the Ghana Science Association Vol. 10 (2) 2008: pp. 20-27