Habitat connectivity and stock structure of the dog snapper (Lutjanus jocu) in the southwestern Atlantic

Although the dog snapper Lutjanus jocu has experienced population declines in the southwestern Atlantic due to overfishing and habitat quality loss, information on the contribution of distinct nursery habitats (NHs) to the exploited populations on adult grounds (AGs) is scarce. We assessed the connectivity among juvenile (n = 98) and adult (n = 69) dog snappers across three NHs and two AGs along over 400 km of a tropical coastline. By identifying otolith multi-elemental signatures using a Random Forest model, we achieved a good overall classification accuracy of 77.2 % (TSS = 0.716). Following a life history criteria in stock delineation, we identified two exploited dog snapper’ stocks that exhibited marked contrasts in nursery origin. The exploited stock from southern upwelling AGs predominantly originated from estuarine environments (84.0 %), suggesting a strong dependence on mangroves. In contrast, stock from northern warm-water AGs displayed a higher diversity in the habitat’s nursery origin, with most individuals coming from the marine environment (75.0 %). Of these, 68.2 % were from their own non-upwelling AGs, consisting of biogenic coral reefs, and 6.8 % from upwelling AGs, characterized by rocky reefs. Barium was the most important element in habitat discrimination, accounting for 31.0 % of the model performance, while other elements, such as Al, Cu, Zn, and Pb contributed less than 10 % each. In conclusion, our results support the existence of two stocks by exhibiting distinct life history traits, that managers may consider when implementing fisheries management measures or designing protected areas.