Hurricane impacts on the foraging patterns of bottlenose dolphins Tursiops truncatus in Mississippi Sound

Acute catastrophic events, such as hurricanes, have various degrees of impact on marine mammal populations. Although changes in environmental conditions of affected areas have been examined for many storms, little attention has been given to the ecological effects on top-level predators. A longitudinal study on bottlenose dolphin Tursiops truncatus behavior and distribution in Mississippi Sound has been ongoing since 2003, allowing the unique opportunity to examine the impacts of the passage of Hurricane Katrina on this coastal dolphin population. Previous research showed an increase in reproductive rates within this population following Hurricane Katrina, most likely due to an increase in prey density following the sharp decline in commercial fishing efforts. In this paper, the frequency and distribution of dolphin foraging encounters in Mississippi Sound were examined from 2003 to 2009, revealing both short-and potentially long-term effects on dolphin foraging patterns following the hurricane. A pulse in dolphin foraging encounters was observed, which increased by similar to 15% in the 2 yr following the hurricane before returning to pre-Katrina levels. Statistically significant hot spots were identified through the use of the Getis-Ord Gi* hot spot analysis and revealed spatial shifts in foraging habitat consistent with prey selectivity. The results of this study support previous findings that coastal bottlenose dolphins in the southeastern United States are selective feeders, preferring to forage in deeper water known for soniferous prey species. Furthermore, this study presents important baseline information for future studies investigating other acute catastrophic events in Mississippi Sound, such as cumulative impacts following the Deepwater Horizon oil spill.