Seasonal Variation in The Biology of Chrysichthys Auratus (Geoffroy Saint-Hillaire, 1809) in Ogun State Estuary, Nigeria

Abstract

This study examined the seasonal variation in the biology of Chrysichthys auratus (Geoffroy Saint-Hillaire, 1809) in Ogun State estuary, Nigeria. Fish were collected in the wet season (May-June, 2018) and dry season (November-December, 2018) from commercial fishermen at the estuary using the bamboo trap. The fish length, weight and other biological parameters were measured and estimated using standard procedures. A total of 432 samples with length ranging between of 10 to 25.9 cm and corresponding weight ranging between 10g to 91g were examined during the two seasons. The wet and dry season showed the peak frequency at size class 14 – 14.9cm and 19 – 19.9cm respectively. The study revealed a the sex ratio (M:F) of 1:0.7 and of 1:0.47 in the wet season and in the dry season respectively. The length-weight relationship showed a negative allometric growth in the wet dry and combined seasons with a “b” value less than 3. Size at maturity were 19.5 cm, 17.30 cm and 18.5 cm for males, females and combined sex respectively in the wet season while in the dry season, all the males were immature and the females attained maturity at a length estimated to be 17.00 cm. The study showed a positive relationship between fecundity and total length of C. auratus in the wet (r² = 0.41) and dry (r² = 0.45) while a positive relationship was also observed between ovary weight and fecundity in the dry season (r² = 0.88) and wet season (r² = 0.83). Seasonal assessment of biology and distribution of C. auratus is recommended to provide requisite information for sustainable management of the species.