Length-weight relationship, Condition factor, Sex ratio, Gonadal Somatic Index and Size at Maturity of Omena, Rastrineobola argentea (Pellegrin, 1904) in Lake Victoria, Kenya.

The present study investigated on Length-weight relationship, Condition factor, Sex ratio, Gonadal Somatic Index (GSI) and Size at Maturity of Omena Rastrineobola argentea. Samples (2240 fish) were collected monthly between August 2014 and March 2015 in the Kenyan waters of Lake Victoria. Results for length-weight relationship revealed that R. argentea experienced positive allometric growth (b>3). The regression slope b was significantly different between the sexes (ANCOVA: F=18.13, p=0.001) and within the stations (ANCOVA: F=10.23, p=0.032). The fish population was dominated by females with an overall male to female ratio of 1.00:1.38. The highest length at 50% maturity (LM50) was recorded in male fish (39.8 mm SL) and the lowest in female fish (35.7 mm SL). The mean (±SE) condition values recorded were 1.096±0.01 in males and 1.097±0.01 in females with range values of 0.78-1.59 and 0.77-1.57 respectively. The condition factor did not differ significantly between male and female fish (Kruskal Wallis test; H = 0.03, p=0.86). The mean (±SE) Gonadal Somatic Index (GSI) recorded were 1.08±0.04 (male) and 6.02±0.14 (female) with range values of 0.02-3.38 and 0.34-17.39 in male and female fish respectively. R. argentea showed peak condition and GSI in September/February and October/March for open waters and Nyanza Gulf respectively. Studies on this fish should therefore not assume isometric growthpattern. The fish has reduced in length at maturity, thus the fisheries managers should revise the mesh-size for the fishery in Lake Victoria.