Miller, Solangi, Kuczaj II. Immediate reponse of Atlantic bottlenose dolphins to high-speed personal watercraft in the Mississippi Sound. Journal of the Marine Biological Association of the United Kingdom (2008), 88:1139-1143 [ABSTRACT, CONTACT AUTHOR]

This study, using opportunistic observations in the Mississippi Sound (a 90-mile intercoastal waterway, between the coast and a series of barrier islands; depths up to 20 feet), evaluated the responses of bottlenose dolphins to the appearance of personal watercraft (jetskis). In just under half the incidents, a dolphin group’s behaviour changing within one minute of the presence of a high-speed personal watercraft. The most notable changes were that groups that were feeding shifted dramatically to “traveling”mode. Interestingly, groups of dolphins that were already in “traveling” mode often paused and began “milling.” In addition, mean dive duration increased dramatically, from 12-16 seconds to 42-82 seconds. Researchers note that “The results demonstrated an immediate, short-term change in dolphin behaviour, suggesting that an increase in the frequency of high-speed personal watercraft in this area could produce long-term detrimental effects.” The authors suggest more research into the differences in reactions to high-speed and lower-speed jetskis and the effects of increasing distance of jetski approach; in addition, they note that long term studies of growth and reproduction in places with different densities of personal watercraft would help clarify any population-level impacts that may accumulate over time.

An interesting sidelight to this research highlights the difficulty inherent in almost all field research of cetaceans: the study took place over two years, four days per month, and resulted in 329 encounters with dolphin groups, among which there 137 instances in which a watercraft passed by. However, only 17 of these 137 were suitable for the study purposes (ie, they were high speed personal watercraft, and 10 minutes of video of the dolphins was captured before the watercraft passed). Two years of diligent study resulted in just 17 useable encounters! And, truthfully, n=17 is pretty impressive compared to most cetacean field studes….