WEIGHT-LENGTH MODELS AND RELATIVE CONDITION FACTORS OF NINE (9) FRESHWATER FISH SPECIES FROM THE YAPEI STRETCH OF THE WHITE VOLTA, GHANA

Abstract

Weight-Length relationships (WLRs) and Relative condition factors (Kn) were estimated for 9 freshwater fish species namely Brycinus leuciscus (Günther, 1867), Hydrocynus forskali (Cuvier, 1819 ), Odaxothrissa mento (Regan, 1917), Labeo coubie (Rüppell, 1832), Labeo parvus (Boulenger, 1902), Labeo senegalensis (Valenciennes, 1842), Distichodus engycephalus (Günther, 1864), Parailia pellucida (Boulenger, 1901)and Schilbe mystus(Linnaeus, 1758)from the lower reaches of the White Volta. Samples were collected from the catches of the artisanal fishermen from October 2011 to March 2012. Using W=aTLb, the weight-length relationships of the species were calculated. Relative condition factors of the species were obtained using the formula: Wo/Wc. The WLRs of all the 9 fish species were highly significant (P<0.001). The determination coefficients (r2) ranged between 0.5764 for Parailia pellucida to 0.9784 for Hydrocynus forskali. The slopes (bvalues) of the WLR regression models of the nine (9) species ranged from 2.0045 to 3.1614 with 95% confidence interval of b for all the nine fish species within 1.386 to 3.352. In terms of growth pattern, 4 out of the 9 species exhibited isometric growth (b=3). Three (3) were observed to have negative allometric growth (b<3) and 2 fish species had positive allometric growth (b>3) patterns. Mean relative condition factors of the species ranged from 1. 00 to 1.09. A T-test of the observed weight (Wo) versus the calculated (Wc) on all the nine (9) species produced no significant difference (P>0.05) between the observed weight and the calculated weight. The models are thus good proxies for approximating the weights of the species.Even though, not all the species exhibited isometric growth, the general wellbeing of the fish specieswas suitable during the study period as inferred from relative condition factors (Kn). This is a contribution of information to support researchers in future and fishery managers for reliable growth estimation and health status of freshwater fishes.