Length-weight relationships, sex ratios and size at first maturity of fishes of lake Ardibo, South Wollo, Ethiopia

Abstract

This study was to investigate some biological aspects of commercially important fishes of Lake Ardibo which was conducted on monthly basis from October 2013 to September 2017 to know Length-weight relationships, sex ratios and size at first maturity of Oreochromis niloticus and Cyprinus carpio. Gillnets of different mesh sizes (6, 8, 10 and 12 stretched mesh size) were used to sample the fishes. Total length (TL) and total body weight (TW) of all species were measured to the nearest 0.1 cm and 1 g, respectively. The results of the study showed that the length-weight relationships for O. niloticus (TW = 0.020TL2.934; n = 243; r2 = 0.936) and for C. carpio (TW = 0.019TL2.845; n = 1436; r2 = 0.927) and showed a curvilinear relationship, signifying the fishes growth were negative allometric growth, O. niloticus have significant difference between sexes (x², P<0.05), However C. carpio was insignificant at (x², P > 0.05) and the size at first sexual maturity (L50) for O. niloticus of females 16.5 cm and 15.4 cm for males and for C. carpio of females 19.23 cm and 19.24 cm for males, respectively. By using the fish growth parameters the Study Lake Fishes were found in poor condition with compared to the fishes that exist in other water bodies in Ethiopia. During our exploratory survey the unregulated open access resource use and uncoordinated water resources development activities were performed which cause degradation of other natural resources in general and fish resources in particular.