Reproductive Biology and Life History Patterns of the Claroteid, Chrysichthys nigrodigitatus (Lacépède: 1803) from a Man-made Lake in Southern Benin

Abstract

Background and Objective: The success of aquaculture and fisheries management of introduced key species requires knowledge on spawning biology. This study aimed to document the reproductive biological traits of Chrysichthys nigrodigitatus from a sand-dragged artificial lake. Methodology: During 15 months, about 1020 individuals were sampled and examined for its spawning characteristics. Sex ratio, gonadosomatic index (GSI), lengths at first sexual maturity (L 50 ) and batch fecundity (F b ) were computed and one-way ANOVA was performed using SPSS computer software. Results: Chrysichthys nigrodigitatus was a prominent species in Lake Ahozon and numerically made about 11.22% of the fish assemblages. The population was dominated by females (67.84%) and showed a sex-ratio of 1:2.1. A delayed maturation was recorded and lengths at sexual maturity (L 50 ) were 20 and 17 cm TL for males and females, respectively. In Lake Ahozon, C. nigrodigitatus spawned all seasons with a peak between April-June. Batch fecundities (F b ) ranged between 350-26040 eggs and significantly (p<0.05) increased with total length (F b = 0.314TL 3,023 , r = 0.81) and body weight (F b = 31.50B W -203, r = 0.74). Egg diameters ranged between 0.30-3.10 mm and frequency distributions evidenced the production of multiple cohorts of eggs with an important stock of offsprings for recruitment. Chrysichthys nigrodigitatus displayed a life history strategy closer to "k" selected that favored its propagation in Lake Ahozon. Conclusion: It is concluded that C. nigrodigitatus is a multiple spawner that reproduces all seasons in the man-made lake, with a peak in wet periods, April-June. The reproductive traits depicted in this special mediumenvironment are useful for fisheries management, aquaculture and species conservation.