Résumé
ABSTRACT Pelagic copepods of the genus Acartia dominate many coastal ecosystems, yet their diversity and ecology remain poorly documented in West Africa. This study reports the first records of Acartia hudsonica and Acartia spinicauda along the southern coast of Cameroon and quantify their seasonal dynamics and environmental associations. Monthly surveys were conducted at 14 stations from May 2021 to January 2022, where zooplankton, temperature, salinity, and chlorophyll a were sampled at ~1.5 m depth and organisms were identified to species level. Habitat suitability was assessed using cumulative frequency distributions with Monte Carlo randomization, and structural equation modelling (SEM) was used to evaluate direct and indirect environmental effects on abundance. Both species exhibited pronounced seasonal variability, with peak abundances during the rainy season. Cumulative frequency distribution analyses revealed partially distinct environmental windows, with both species occurring across broad temperature (26–32°C) and salinity (4–25) ranges. SEM indicated that temperature was the primary driver of seasonal dynamics, while salinity exerted a negative effect on A. hudsonica. Chlorophyll-a showed a consistent negative association with abundance in both species. These results demonstrate that non-indigenous Acartia species can establish and persist in dynamic tropical coastal environments by exploiting broad environmental tolerances and seasonal hydrographic variability, and provide a quantitative baseline for monitoring their spread in the Gulf of Guinea.