Weight-length and total length-standard length factor relationships, and condition factor of the main fish species in Lake Maabo, Chad (Central Africa)

Abstract

The fish communities of Lake Maabo are little studied despite the increasing fishing effort on this ecosystem. The present study aims to  establish weight-length (Pt = a Lt b) and total length-standard length (LT = p + q LS) relationships, and to determine the condition factor  of the main species of Lake Maabo. To this end, morphometric data were collected monthly between January 2016 and December 2019 from artisanal fisheries. A total of 4,891 specimens belonging to 25 commercial fish species were caught using various fishing gears and
techniques. The regression coefficient b ranged from 1.17 (Hydrocynus forskali) to 4.69 in (Ctenopoma kingsleyae). Two species showed positive allometric growth, 2 with isometric growth and 21 species with negative allometric growth. The total length-standard length relationship was positive and significant for all species (r2 between 0.666 and 0.999). Only Tetraodon lineatus had a condition factor within the range recommended for mature tropical freshwater fish. The condition factor ranged from 0.536±0.182 to 3.810±0.850, with an  overall mean of 1.804±0.833. These results showed that fish in Lake Maabo are under increasing anthropogenic pressure. They show the  need to study the population dynamics of the most exploited species in that Lake.