Ranging patterns of common bottlenose dolphins Tursiops truncatus in Barataria Bay, Louisiana, following the Deepwater Horizon oil spill

Common bottlenose dolphins Tursiops truncatus were present in Barataria Bay, Louisiana, USA, before, during, and after the 2010 Deepwater Horizon oil spill. Health assessments conducted on dolphins in Barataria Bay in 2011, 2013, and 2014, after the capping of the well, found disease conditions consistent with petroleum hydrocarbon exposure and toxicity. Satellite-linked transmitters were affixed to dolphins during these health assessments for assessing the potential for continued exposure to petroleum-associated products, estimating survival rates, and planning potential restoration. In total, 44 tags were deployed, transmitting for 48 to 260 d. The dolphins exhibited multi-year site fidelity to small home ranges. Most tagged dolphin locations were inside the bay. On average, the dolphins that entered the Gulf coastal waters remained within 1.75 km of shore. No dolphins were documented more than 14 km beyond their 95% utilization distribution (UD) overall home ranges. Individual variation in the use of specific regions and habitats of Barataria Bay suggests the occurrence of community structure. All but 3 of the dolphins (93%) were tracked or observed during more than 1 yr in Barataria Bay, with 20 (45%) recorded each year from 2010 to 2014. All but 6 dolphins (86%) were tracked during multiple seasons. Home range sizes were comparable to those reported for bottlenose dolphins elsewhere. These findings suggest the occurrence of long-term, year-round residency. Residency patterns suggest potential for continued exposure to petroleum-associated products that may have remained in Barataria Bay after the spill.