Morphometric characteristics and condition factor of Chrysichthys nigrodigitatus (Lacepede, 1803) and Sarotherodon melanotheron (Ruppell, 1852) in the Lagos Lagoon
One hundred and fifty (150) specimens of Sarotherodon melanotheron and 150 specimens of Chrysichthys nigrodigitatus were collected from Better-life Fish Market in Makoko area of Lagos State between June-August 2016 to provide information on the size distribution, length-weight relationship, determine regression equation and coefficient of determination of morphometric parameters and condition factor of the species. Size ranges of 10-22 cm and 15-33 cm were observed in S. melanotheron (20-158 g) and C. nigrodigitatus (30-279 g) respectively. Length-weight relationship of S. melanotheron and C. nigrodigitatus were described by the equation Log W = -1.107 + 2.4478 Log L and Log W = -1.9287 + 2.8484 Log L respectively. The b values (growth exponent), 2.4478 and 2.8484 for body weight on total length of S. melanotheron and C. nigrodigitatus respectively indicate negative allometric growth which implies that the fishes become slenderer as they increase in weight. The least coefficient of determination (r2), 0.4305 (S. melanotheron) and 0.2221 (C. nigrodigitatus) were obtained in snout length on total length and pelvic fin length on total length respectively. High values coefficient of determination, obtained indicates a high degree of positive correlation between the different morphometric parameters with the reference length (total length). All mean condition factors (k) calculated for species, size classes and sexes are all above 1 and this reveals that they are all in good conditions and that the environment is suitable for both species with regards to the feeding condition. This study provides some biological information on the condition of the species in the Lagos Lagoon as at the period of the study.
Keywords: Morphometric characteristics; condition factor; Chrysichthys nigrodigitatus; Sarotherodon melanotheron; Lagos Lagoon.