Spring ichthyoplankton communities in the northern Canary Current upwelling ecosystem

The Atlanto-Iberian continental shelf, located in the northern part of the Canary Current upwelling system (North Atlantic Ocean), is a highly productive and dynamic region (spatially and temporally), supporting a high diversity of marine organisms. However, current information on fish larval assemblages is absent. This study provides the first large-scale assessment of the composition and spatial distribution of ichthyoplankton communities along the western and southern Iberian coasts in spring (April/May). Fish larvae assemblages were compared between four regions with different oceanographic conditions: Northwest Iberia (NW), Southwestern Iberia (SW), Western Gulf of Cadiz (S) and Eastern Gulf of Cadiz (Cad). A total of 57 fish species and 12 genera, belonging to 26 families were recorded, with Alosidae, Gobiidae, Callionymidae, Sparidae, and Blenniidae being the most abundant families. The communities were dominated by small pelagic species ( Sardina pilchardus and Engraulis encrasicolus ) . A latitudinal gradient in community structure was observed, broadly reflecting the environmental temperature gradient. The eastern Gulf of Cadiz (Cad) presented a different larval community structure and the highest abundance of fish larvae. These patterns suggest that local spring conditions of productivity, temperature and retention favour fish reproduction, as evidenced by the high abundance of Engraulis encrasicolus , Sardina pilchardus and Diplodus sp.. Temperature, salinity and depth were identified as the main environmental drivers shaping larval community structure. This study provides valuable baseline information for future research to underpin biodiversity conservation and fisheries management efforts, especially in biogeographic transition zones where spawning patterns and population dynamics are likely to shift under climate change scenarios.