Sex Ratio And fecundity Of Chrysichthys Nigrodigitatus (Family - Claroteidae) From Asejire Lake, Nigeria

Abstract

Sex ratio and fecundity of Chrysichthys nigrodigitatus from Asejire Lake were examined. The length-weight relationship showed that weight was curvilinearly related to standard length. The logarithm transformation of weight against standard length gave a straight-line graph represented
by the following equation:

 Log W = -0.66 + 2.13 Log sl 

       r² = 0.854; (p<0.001) n = 209 

Males were generally more with a male : female ratio of I:0.18. The average fish weight was 88.97g (16.28 cm standard length). Sexual maturity was attained at an average size of 45.0g (14.0 cm standard length). Relative fecundity was dependent on body weight and standard length (P <0.05 and P < 0.01 respectively). Chrysichthys nigrodigitatus expended between 0. 75%- 27.30% of body weight in egg production. The condition factor values showed that a female specimen of equal length with a male specimen is heavier. Six gonad maturity stages were identified, ovary and gonad weights increased with stage of maturity.

Keywords: Chrysichthys nigrodigitatus; body weight; standard length; condition factor; gonads.