Morphometric and meristic characteristics of silver catfish Chrysichthys nigrodigitatus (Lacepède, 1803) (Siluriformes: Claroteidae) from Epe Lagoon, Lagos, Southwest Nigeria
The morphometric and meristic characteristics of 300 fish samples of silver catfish Chrysichthys nigrodigitatus (Lacepède, 1803) (Siluriformes: Claroteidae) inhabiting the Epe Lagoon, Lagos, was conducted between October 2012 and January 2013 in order to investigate the growth and health status of this species. The meristic characteristics deduced in this study were counted and ranged as follows; dorsal spine had constant value of one all through, and the pectoral spine had a constant value of two, dorsal rays were counted 6-7 (6.03 +/- 0.25), pectoral rays were counted 6-7 (6.04 +/- 0.27), gill rakers were counted 15-18 (17.86 +/- 0.96), opercula bones were counted 2-4 (3.22 +/- 1.11) and vertebrae count was 8-10 (8.43 +/- 1.95). All the morphometric characteristics except body weight were measured with measuring board of precision of 0.1 cm. Body weight was measured with a metler electronic chemical balance of precision of 0.1 g. Morphometric data includes total length 15.5-38.5 cm (25.43 +/- 3.87 cm), fork length 2.0-11.6 cm (8.61 +/- 1.53 cm), standard length 10.0-28.3 cm (17.85 +/- 3.90 cm), head length 2.0-3.5 cm (2.91 +/- 0.79 cm), head depth 1.0-3.3 cm (2.41 +/- 1.05 cm), eye diameter 0.5 1.0 cm (1.28 +/- 0.77 cm), body depth 1.6-6.5 cm (3.57 +/- 0.90 cm) and body weight 24.5-451.6 g (157.48 +/- 5.60 g). The length and the weight of this species were not directly proportional. Growth parameter has a negative allometric range (b = 0.256) and the condition factor (k) ranged from 0.103-2.97 (1.08 +/- 0.64) which indicated a good condition of the fish species in the Lagoon. This study provided baselines of the population structure of this species in Epe Lagoon, Lagos State and also shown that their present growth pattern calls for further monitoring.