Effects of Broodstock Sex Pairing Ratios and Resting Periods of the Nile Tilapia Oreochromis Niloticus (Linnaeus, 1758) on Fry Production

Abstract

The Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) forms about 80% of farmed fish in Ghana. However, the unavailability of its seed all year round for culture is a major constraint. This study evaluated the effects of varying male to female broodstock pairing ratios of 1:1, 1:2 and 1:3 with resting intervals of 0, 3 and 7 days on fry production performance of the Akosombo strain of the Nile tilapia at the Ashaiman Aquaculture Demonstration Centre, Ghana. Nine (9) treatments were arranged according to a 2 x 3 factorial design with three replicates giving a total of 27 spawning hapas (1 m3). Male and female brooders of mean body weight (200±50 g and 171±23.7 g respectively) were paired according to the three different sex ratios. Water quality parameters for temperature and DO were taken daily while’s pH, salinity and ammonia were measured weekly. The total mean fry output for the sex pairing ratios (1:1, 1:2, 1:3) were 716±344, 973±325 and 723±577 respectively. The total fry output for 0, 3 and 7 days of resting were 1503±868, 2030±637 and 3051±1054 respectively with an observed 35% (3 days rest) and 103% (7 days rest) fry production increment over the 0 resting treatment. With respect to the combined effect of varying sex ratios and resting periods, the highest mean fry production (701±405) was attained under the 7 days resting period at a pairing ratio of 1:2. Although results subjected to ANOVA showed no significant differences (p>0.05) among the treatments, the relatively high reproductive performance observed for broodstock pairing ratio 1:2 and resting period of 7 days under this study confirms that it is a more efficient broodstock management technique for an increased Nile tilapia fry production.