Length-Weight Relationship and Condition Factor of Three Cichlids from the Tono Dam, Ghana

Abstract

The length-weight relationship (LWR) and condition factor of three Cichlids, namely, Sarotherodon galilaeus, Coptodon zillii and Oreochromis niloticus from the Tono dam in Ghana, were investigated. A total of 1,870 individuals of the target species were randomly collected from 20 artisanal fishermen using gill nets to fish from January to December 2015. Each species was sorted by sex, and each fish's total length (L) and body weight (W) were measured and recorded. Simple linear regression plots of weight against length were computed, and the slope of the regression line, ‘b’ and intercept of the regression line, ‘a’ of each species (male, female, and mixed sexes) were derived. Their condition factor (K) was estimated using the relationship, K = 100W/L³. The total length and body weight of the three species ranged from 5.0 - 21.5 cm for O. niloticus, 2.1 - 19.5 cm for S. galilaeus, and 4.5 - 19.5 cm for C. zillii, while their body weight ranged from 08.0 - 282.0 g for O. niloticus, 10.0 - 270.0 g for S. galilaeus and 10.0 - 210.0 g for C. zillii. All three species exhibited a positive allometric growth pattern, except for females of S. galilaeus. The coefficient of determination values ranged between 0.954 and 0.972 in all three species, which showed a high degree of positive correlation between the L and W of all the fish. The monthly mean condition factor (K) estimated for each species ranged from 4.23 to 5.39 for O. niloticus, 4.21 to 5.32 for S. galilaeus, and 2.29 to 5.20 for C. zillii. The high condition factors (K) recorded in this study indicate that the fish stock is in excellent health, benefiting from good food availability, favorable environmental conditions, and low-stress levels. These findings suggest that the habitat provides optimal resources for growth and survival, contributing to the overall well-being of the fish.