Short-term effects of boat traffic on bottlenose dolphins, Tursiops truncatus, in Sarasota Bay, Florida

Coastal cetaceans are subject to potential injury or disturbance from vesse ls. In Sarasota, Florida, where about 120 resident bottlenose dolphins, Tur siops truncatus, share the inshore waters with over 34,000 registered boats , disturbance potential is high. We assessed specific behavioral responses of individual dolphins to boat traffic. We conducted focal animal behaviora l observations during opportunistic and experimental boat approaches involv ing 33 well-known identifiable individual bottlenose dolphins. Dolphins had longer interbreath intervals (IBI) during boat approaches compared to cont rol periods (no boats within 100 m). Treatment IBI length was inversely cor related with distance to the nearest boat in opportunistic observations. Du ring 58 experimental approaches to 18 individuals, a video system suspended from a tethered airship was used to observe subsurface responses of focal dolphins as boats under our control, operating at specified speeds, were di rected near dolphins. Dolphins decreased interanimal distance, changed head ing, and increased swimming speed significantly more often in response to a n approaching vessel than during control periods, Probability of change for both interanimal distance and heading increased when dolphins were approac hed while in shallow water. Our findings provide additional support for the need to consider disturbance in management plans for cetacean conservation .