Ontogenetic resource utilization and migration reconstruction with δ13C values of essential amino acids in the Cynoscion acoupa otolith

1. With the increasing anthropogenic impacts on fish habitats, it has become more important to understand which primary resources sustain fish populations. This resource utilization can differ between fish life stages and individuals can migrate between habitats in search of resources. Such lifetime information is difficult to obtain due to the large spatial and temporal scales of fish behaviour. The otolith organic matrix has the potential to indicate this resource utilization and migration with δ13C values of essential amino acids (EAAs), which are a direct indication of the primary producers. 2. In a proof-of-concept study, we selected the Acoupa weakfish, Cynoscion acoupa, as a model fish species with distinct ontogenetic migration patterns. While it inhabits the Brazilian mangrove estuaries during juvenile stages, it moves to the coastal shelf as an adult. Thus, we expected that lifetime resource utilization and migration would be reflected in δ13CEAA patterns and baseline values i...