Life-history-dependent and seasonally varying distribution patterns of Atlantic bigeye (Priacanthus arenatus) in western African coast

Understanding spatiotemporal distribution patterns of fish across life history stages is critical for sustainable fishery management, particularly in data-poor regions such as the extensive yet poorly explored western African coastal regions. This study investigates the distribution patterns and ontogenetic habitat shifts of Atlantic bigeye (Priacanthus arenatus) at various life stages on the coast of Sierra Leone using data from twelve cruises conducted between 2019 and 2021. Our results reveal distinct life-stage partitioning across multiple life stages of Atlantic bigeye. Juveniles (<60 mm body length) predominantly distribute in the pelagic waters beyond the continental shelf. As individuals reach a body length of approximately 60 mm, they enter the sub-adult stage, characterized by the onset of gonad development and a noticeable migration to demersal areas within the continental shelf. Adults (≥150 mm body length) are basically demersal as populations primarily distribute in demersal areas within the continental shelf. Our observations also suggest that juvenile Atlantic bigeye exhibits capture peaks: one prior to the rainy season (April–May) and the other after the rainy season (September–October), suggesting a potential correlation with spawning. Moreover, the extensive offshore distribution of juveniles beyond the continental shelf appears to be closely associated with seasonal river plume spread, potentially reflecting a behavioral adaptation to utilize oceanic dispersal pathways during periods of enhanced freshwater input. These findings fill a critical knowledge gap and provide a scientific basis for fisheries research and management of this species in western African waters.