Habitat use plasticity by the dog snapper (Lutjanus jocu) across the Abrolhos Bank shelf, eastern Brazil, inferred from otolith chemistry

Abstract

Many reef fishes move between different coastal systems throughout their ontogeny, but these movements are complex and often not understood. In this study, we examined how the dog snapper (Lutjanus jocu) uses marine and estuarine habitats across the Abrolhos Bank shelf (eastern Brazil) through the analysis of elemental signatures in otoliths. Specimens were sampled in an estuary and adjacent marine region. Ba/Ca, Sr/Ca, Mg/Ca and Mn/Ca were measured by LA-ICPMS along the otolith growth axis to cover the entire lifetime of the individual. Change-point analysis, principal component analysis and BRT modeling were used for the objective identification of habitat-use patterns of the species. Otolith Ba/Ca ratios performed better than other elements for tracking L. jocu movements between estuarine and marine habitats, which may result from small variations in salinity and high turbidity levels, as these characteristics are typical of the Abrolhos Bank. Two contrasting habitat-use patterns were identified for L. jocu: i) marine residents (56% of sampled fish) - fish that remain in marine systems throughout their lifetime; and ii) marine migrants (37%) - juveniles inhabit estuaries and move to marine systems with age. These categories were successfully re-classified, which suggests that they are coherent and reliable. Following recent findings of flexible habitat-use patterns in many other fish species, L. jocu habitat requirements also appear to be quite malleable. As the dog snapper has been facing commercial overexploitation in the region, this plasticity in habitat use should be considered in future fisheries management.