Influence of environmental conditions on the abundance of juvenile endangered Atlantic weasel shark (Paragaleus pectoralis) in an African nursery area

Abstract Identifying and monitoring nursery habitats is crucial for shark conservation, especially for species threatened with extinction. The aim of this study was to explore inter- and intra-annual changes (between 2016 and 2025) in the abundance, size, and sex ratio of the poorly studied, endemic, and endangered Atlantic weasel shark ( Paragaleus pectoralis ) in the nursery of Sal Rei Bay (Boa Vista Island, Cabo Verde) and investigate how such changes relate to local environmental conditions. From 2016 to 2025, 150 individuals were sampled (71 females and 79 males) with total length (TL) ranging from 41.5 to 98 cm (mean = 56 ± 10 cm). Catch per unit effort (CPUE; number of individuals caught per hour per square meter of net) varied among years, attaining the highest value in 2025 (0.10 individuals h −1 m 2 ), and among months, with increased abundance observed in February and May–July. Smaller individuals (less than 55 cm TL) were mostly found between May and July, suggesting that parturition likely occurs during these months. Of four candidate environmental variables assessed (sea surface temperature, dissolved oxygen, salinity, and chlorophyll a), temperature and oxygen had a significant effect on P. pectoralis abundance, with CPUE increasing with rising temperatures (peaking at ~ 26–27 °C) and with higher oxygen concentrations. Our findings indicate that Sal Rei Bay may serve as a potential nursery area for this endangered shark species, providing key information for national authorities and conservationists to safeguard this critical habitat, namely through its designation as a marine protected area.