Length-Weight Relationships, Condition Factor and Fecundity of the West Africa Freshwater Crab, Sudanonautes africanus (Milne-Edwards 1883), in Western Nigeria

Abstract

The length-weight relationships, condition factor and fecundity of the West-African freshwater crab, Sudanonautes africanus, was studied from different freshwater bodies within south-western Nigeria. The crabs were separated into males (151) and females (112). The length-weight relationship, condition factors, and fecundity of the crabs were determined. Growth parameters a and b of the length-weight relationship, (LWR) w = aLb, for S. africanus was 0.889, 5.029 and 0.713 for males, females and entire population, respectively. The values of b estimated were 2.475, 3.185 and 2.567 for males, females and whole population, respectively. The regression equation for the LWR are W= - 0.046 + 2.475L for males, W= 0.717+3.185L for females and W= - 0. 147 + 2.567L for the total crab population. The coefficient of determination of males, females and entire population were 0.716, 1.049 and 0.699, respectively, showing a strong correlation between the variables. There was a strong relationship (r2 = 0.81) between length and weight of males and females and the entire crab population. The LWR was allometric for all crabs. Results also show that there is a weak correlation (r2 = 0.36) between fecundity and total body weight (BW)/carapace length (CL) of the crabs. The length-weight distribution pattern did not show remarkable differences between species, sexes, and populations. Length-weight relationships have no influence on the fecundity. Mean (± SE) fecundity (292.8 ± 76.07 eggs) was positively related (r2 = 0.75) to CL. Fecundity ranged between 120 and 449 eggs with a mean diameter of 1.66 mm ± 0.068 mm. No relationship between egg size and carapace length was found. There was no significant difference (P > 0.01) in condition factors between the sexes.