Baseline elemental profile of juvenile sharks from a multispecies nursery area off West Africa (Sal Rei Bay, Boa Vista Island, Cabo Verde).

Establishing baseline descriptions of inorganic elements in early shark life stages and nursery habitats is essential for assessing anthropogenic impacts and supporting conservation strategies. This study presents the first baseline of plasma trace element concentrations (Al, Zn, As, Cu, Cr, Cd, Co, Mn, Ti, Ni, Hg, Pb) for four juvenile shark species (Carcharhinus limbatus, Paragaleus pectoralis, Rhizoprionodon acutus, and Sphyrna lewini) from Sal Rei Bay (Cabo Verde), the first multi-species shark nursery area described in Atlantic Africa. Seawater and sediment samples were collected from eight sites and analyzed along with plasma samples using total reflection X-ray fluorescence spectroscopy (TXRF). Sediment granulometry and pollution indices, including the enrichment factor (EF), ecological risk index (RI), and metal pollution index (MPI), were used to characterize habitat contamination. Linear and generalized additive models (GAMs) were applied to assess site- and element-specific patterns in the environment and shark plasma. Overall, environmental contamination was low, with slight increases in Cd, Co, and Hg in both water and sediment samples near the fishing port (sites 1 and 2) and at site 5, likely reflecting natural transport, sediment redistribution, and enhanced nearshore deposition. Correspondingly, juvenile sharks exhibited generally low plasma trace element concentrations, although species-specific elemental signatures were evident: elevated Al and Cu levels in C. limbatus, Zn levels in S. lewini and As levels in R. acutus and P. pectoralis. These findings establish critical baseline values for future biomonitoring and support conservation and management of Cabo Verdean shark nursery habitats.