Sex Ratio and Allometry of Synodontis melanoptera and Hydrocynus forskalii in a Man-made Lake, Nigeria

摘要

Background and Objective: Sex ratio and allometry provide key information necessary for assessing reproductive potential and estimating stock size in fish populations. Sustainable management of dwindling commercially important fish stock in Nigerian inland water depend on adequate knowledge of the biological status of such fish species. Therefore, sex ratio and allometry of Synodontis melanoptera and Hydrocynus forskalii from Lake Alau, were investigated to enhance their production. Materials and Methods: A total of 512 fish samples comprising 252 S. melanoptera and 260 H. forskalii were randomly collected from fishers catch weekly for a period of 3 months. Length and weight were individually measured following standard procedure and sexes were separated after dissection. Length-weight relationship was estimated according to linear regression model W = aLsupb/sup and condition factor determined using the equation K = 100.W/Lsup3/sup. Results: The mean length and weight for S. melanoptera and H. forskalii were 11.49±2.71 cm; 36.06±21.76 g and 11.91±3.53 cm; 29.52±15.44 g, respectively. The growth coefficient ‘b’ ranged from 2.802-3.177 for S. melanoptera and 2.230-2.707 for H. forskalii . While, the mean condition factors varied from 1.81±0.83-2.49±1.83 for S. melanoptera and 1.24±1.04-2.03±2.14 for H. forskalii . The sex ratio was 1:1.03 in S. melanoptera and 1:1 in H. forskalii , male:female, respectively. Conclusion: The growth of both species was allometric and the condition factors indicate a good state of well-being in the reservoir.