Migratory Patterns of Centropomus parallelus across Estuaries of the Abrolhos Bank Shelf as Determined by Otolith Elemental Analysis ^†

The fat snook (Centropomus parallelus Poey, 1860) is an important recreational and commercial amphidromous fish species along Brazilian coastal environments. Herein, we used otolith elemental analysis to investigate migratory patterns of C. parallelus across estuaries from Abrolhos Bank shelf, eastern Brazil. Ninety-four adults were sampled between January and April 2019 in four estuaries, including the Rio Doce, Ipiranga, São Mateus (in Espírito Santo estate), and Caravelas (in Bahia estate). The individuals were weighed, measured, and sagittal otoliths were removed, cleaned, and prepared for further microchemical analyses. The migratory patterns were compared between estuaries through the elemental composition profile (Sr:Ca ratio), from core to edge of otoliths, considering that Sr:Ca ratios (mmol/mol) from 2–5, 5–8, and 8–11 mmol/mol were considered fresh, estuarine, and seawater residency, respectively. The Sr:Ca ratio profiles indicated seven distinct habitat-use patterns. Considering all individuals, 43% were estuarine residents (type 2), 27% were migrants between estuarine and saltwater (type 6), and 16% were migrants between estuarine and freshwater (type 5). Considering each estuary, in Rio Doce, Ipiranga, and São Mateus, 32%, 71%, and 45% of fish were classified as type 2, respectively. In the Caravelas estuary, 58% were classified as type 6. Types 1, 3, 4, and 7 presented 3%, 3%, 6%, and 2%, respectively Our data show that C. parallelus can occupy diverse salinity habitats and migrate among marine, estuarine, and freshwater areas, showing high environmental plasticity and adaptation throughout their lifetime. The conservation of this species requires the preservation of freshwater and marine environments, but mainly estuaries, which allows the connectivity between habitats.