Etude de la reproduction du tilapia du Nil Oreochromis niloticus (l.) en captivite dans les eaux geothermales du sud Tunisien.

Abstract

This study was conducted to assess the first maturity size, the fecundity and the best size of females to maximize and enhance the production of larvae in females Nile tilapia Oreochromis niloticus reared in the geothermal waters in southern Tunisia. The results showed that Nile tilapia reach sexual maturity at a small size, during the first year of life. The total lengths (TL) at first sexual maturity (Lm sub(-2) ) are 11.28 cm and 12.46 cm, respectively for females and males. The female O. niloticus has a low absolute fecundity (F) which varies between 241 and 1358 eggs respectively for females of 15.5 and 24.1 cm (TL). This fecundity is related to female size by the equation: F = 1.77 TL super(1,96) The comparison of three size-classes of females (15.3, 20.5 and 25.6 cm) on the reproductive performances showed that females of 20.5 cm (TL) present the best productivity (32 larvae m super(-2) day super(-1) ). The low productivity of large females (12 larvae m super(-2) day super(-1) ) is related to the decreases of the female activity (i.e. participation rate 21% versus 87% for the size 15.3 cm) and to their low spawning frequency.