Growth and reproduction of two cichlids Tilapia zilliiand Hemichromis bimaculatus (Teleostei: Cichliformes) in the Saharan hydrosystems (Algeria)

In this study, we have studied the length-weight relationship, condition factor (Kr), gonado-somatic index (GSI) and size at first maturity of two Cichlidae species (Tilapia zillii andHemichromis bimaculatus) from two lakes (Megarine and Temacine) of the northern Sahara (Algeria). Some 159 specimens of H. bimaculatusand 52 T. zilliiwere sampled between September 2012 and July 2013. The length-weight relationship revealed an isometricvalue b (3.0) for H. bimaculatusfrom Lake Megarine, while there was no significant difference for T. zilliifrom Lake Temacine. We noted a negative allometric growth pattern (b<3) of males and females of H. bimaculatus. Both sexes of T. zilliigrew isometrically. The Kr did not differ significantly between months for the two studied species. It was less than 1 only in November and July for H. bimaculatus. For T. zillii, the monthly mean of Kr was always greater than 1 for all the studied period. The firstsexual maturity of 50% of males was observed at 52.75mm in H. bimaculatusand 61mm in T. zillii. The smallest mature female had a total length of 60.26mm and 66mm for H. bimaculatusand T. zilliirespectively. The reproduction period of H. bimaculatusandT. zilliibegins in March with an extended spawning period. The overall sex ratio was in favor of females (1: 0.7) in H. bimaculatus, and in favor of males in T. zillii(1: 1.33). For both species, the sex ratio varied according to months and size classes.