An Aspect of Reproductive Potential of Sarotherodon Galilaeus and Oreochromis Niloticus in the Golinga Reservoir in Northern Region, Ghana

The study looked at the reproduction potential of Orochromis niloticus and Sarotherodon galilaeus in the Golinga reservoir between November 2006 and April 2007, by assessing the stages of gonad development, fecundity, condition and physico-chemical parameters including temperature, pH, dissolved oxygen and turbidity. For Oreochromis niloticus, a total of 115 fishes were obtained during the study period, 42 males (36.52%) and females 73 (63.58%). Out of the 73 females 14 were gravid with the following stages of gonad development, expressed as percentages: immature (White) = 7.14% maturing (yellow) =7.14% , ripe (deep green) = 50% and spent (red, flaccid) = 35.7% . The total number of Sarotherodon galilaues that were encountered during the study period were 191, with 74 males (35%) and 117 females (65%). Off the 117 females 35 were gravid of which 7 have immature gonads (20%), 15 maturing gonads (43%) and 13 ripe gonads (37%). The study showed a preponderance of females in both cichlids with sex ratios (male:females) for both cichlids were 1:1.7 and 1:1.5 for O. niliticus and S. galaeus respectively. The monthly Gonado-Somatic Index (GSI) of females ranged from 0.24 to 4.49 with higher GSI values recorded in April. The pattern of gonad development for females indicated that the spawning was not synchronized in both cichlids. In spite of the variation in the gonadal stages of females, the periodicity of spawning for O. niloticus and S. galilaeus at Golinga indicates that the breeding season and the reproductive cycle begins around January and reaches its peak in April-May where there is increase in food abundance from run-off during the onset of the rains. The fecundity range from 162 to 874 for O. niloticus and 299 to 1768 for S. galilaeus. The above fecundity statistics for O. niloticus and S. galilaeus, shows that, S. galilaues is more fecund than O. niloticus. Also with the biparental mouth brooding nature of S. galilaeus it suggest that more offspring could be raised than in the case of O. niluticus. The condition factor (K) was higher in S. galilaeus than in O. niloticus as 2.81 – 4.07 and 5.0- 9.7 respectively. This suggest that S. galilaeus are in a better condition that O. niloticus, nevertheless both cichlids were in good condition. The physico-chemical parameters generally are optimal and do not have any effects on the survival, growth and reproduction of O. niloticus and S. galilaeus.