Biological Aspects, Catch and Length Distribution of African Catfish, Clarias gariepinus and Common Carp, Cyprinus Carpio in in Lake Lugo, South Wollo, Ethiopia

Abstract

Determining biological parameters such as length to weight relationship, sex ratio and size at first maturity of threatened fishes give good information on their growth performance and help manage and conserve fish populations in their natural water bodies. In this study, some biological parameters were reported for Clarias gariepinus and Cyprinus carpio. Samples were taken at monthly intervals from October 2013 to September 2017 in Lake Lugo, South Wollo, Ethiopia. The objective of the study was to determine length to weight relationships, length class frequency, sex ratio and size at first maturity of the fishes. Total length (TL) of the species was measured to the nearest 0.1 cm and total body weight (TW) to the nearest 1 g. The physico-chemical parameters were also measured: transparency by using secchi disk, conductivity by Wagtach International conductivity meter and pH by pH meter. The results showed that the parameters were within the permissible limits except the pH level at Gedam Sefar sampling site. A total of 672 fish specimens were collected. Length (cm) to weight (g) relationship for C. gariepinus was sketched as: TW = 0.015TL^2.8, n = 81, r² = 0.901 and for C. carpio as: TW = 0.018TL^2.85, n = 591, r² = 0.926, which, in both cases, showed a curvilinear relationship, signifying the fishes followed negative allometric growth. The sex ratio between males to females showed significant difference (C. gariepinus: χ² = 4.46, P<0.05; C. carpio: χ² = 12.0, P<0.05). Size at first sexual maturity (L₅₀) for C. gariepinus was 31.7 cm for females and 31.1 cm for males, while L₅₀ for C. carpio was 19.2 cm for females and 19.3 cm for males.