Seasonal and sex influences on gonadosomatic index of <i>Brycinus nurse</i> (Burchell, 1832) in Goronyo Reservoir, Sokoto State, Nigeria

Reproductive studies in fishes include investigating Gonado-somatic index (GSI). Lack of adequate information on reproductive indices of Brycinus nurse species in Goronyo reservoir has constituted a major setback in developing management plan for the species. Therefore, this study was designed to investigate the influences of season and sex on GSI of B. nurse species in Goronyo reservoir, Sokoto state Nigeria. The study was conducted at Rimawa, Katsira and Kaita landing sites of the reservoir. The species was sampled monthly for two years using gillnets, clap nets, traps, hooks and line fishing gears. Data on GSI was taken in accordance with the standard established procedures. The data were analyzed using descriptive statistics and independent sample t-test at 5% significance level. The results of the study revealed that 446 individuals (58.50%) are males and largely sampled between June and July. Majority of the sampled males were at stage III while the females were at stages IV and VI of gonads morphological maturation with heavier gonads showing seasonal variations. The mean GSI value was influenced by sex and season with highest (7.12%±0.58) in females and 3.99%±0.31 in males occurring in July. The study concluded that seasonal variations and sex influenced the GSI metric of B. nurse species in Goronyo reservoir. Therefore, the study recommended the use of GSI for estimating the B. nurse maturity ogive in Goronyo reservoir.