Foraging habits and levels of mercury in a resident population of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro Archipelago, Caribbean Sea, Panama

Abstract

A small and genetically isolated bottlenose dolphin (Tursiops truncatus) population resides year-round in the Bocas del Toro Archipelago-Panama (BDT). Photo-identification and genetic data showed that this dolphin population is highly phylopatric and is formed exclusively by individuals of the “inshore form”. This study aimed to investigate the trophic ecology and mercury concentrations of bottlenose dolphins in BDT to assess their coastal habits. We collected muscle samples (n=175) of 11 potential fish prey species, and skin samples from free-ranging dolphins in BDT (n=37) and La Guajira-Colombia (n=7) to compare isotopic niche width. Results showed that BDT dolphins have a coastal feeding habit, belong to the “inshore form” (δ13C=−13.05 ± 1.89‰), and have low mercury concentrations (mean=1637 ± 1387 ng g−1dw). However, this element is biomagnified in the BDT food chain, showing a marginal dolphins health risk (RQ=1.00). We call for a monitoring pollutant program and conservation strategies aimed to protect the dolphin population at BDT.