Reproductive dynamics of Atlantic chub mackerel Scomber colias Gmelin, 1789 in Senegalese waters

The Atlantic chub mackerel (Scomber colias) is an ecologically and commercially important species supporting artisanal and industrial fisheries in West Africa. This study updates critical reproductive parameters for S. colias in Senegalese waters to inform stock assessment and sustainable management of small pelagic fisheries within the Senegalese Exclusive Economic Zone. Based on 1134 specimens monthly sampled from commercial landings along the Petite Côte (June 2019-May 2020), sex ratio, spawning season and size at first sexual maturity (TL₅₀) were analysed. The overall sex ratio favoured females (64%), with significant size-dependent variation (χ² test, p-value <0.05). Spawning occurred from November to February, peaking in December, as indicated by gonado-somatic index (GSI) trends (Kruskal-Wallis test, p-value <0.001) and maturity stage frequencies. The TL₅₀ was estimated at 28.7 cm for males, 28.8 cm for females and 28.8 cm for combined sexes. These findings align with regional patterns but highlight local specificities, such as a slightly later spawning peak compared to northern Northwest African waters. The results provide actionable reference points for fisheries management, including potential seasonal closures (November-February) and a minimum landing size (~29 cm TL).