Ambient Noise Measurements in and Around the Gulfport Mississippi Harbor and its Potential Influence on Marine Mammals

A pilot program designed to measure ambient noise and record dolphin echolocation signatures at the entrance to the Gulfport harbor was carried out from May 2005 to July 2005. This non-invasive study used a passive acoustic monitoring system. These results showed that during the month of May, dolphin echo ranging clicks were easily identified by their broadband spectra and in many cases correlated with visual observations of dolphin activity in the area. Signatures of large and small ships entering and leaving the harbor area were also recorded. The animals did not appear to be affected by the noise generated by the small boats. However, when several large container ships entered and left the Gulfport harbor, there was little evidence of any dolphin echolocation signals and no dolphin were observed in the immediate area. Their absence may be due to the high levels of broadband noise radiated from these ships. These long-term observations also show that, even after sunset, dolphin echolocation signals were recorded indicating that the animals are continuing to be active during the nighttime hours. Work unit no. M297. Prepared in collaboration with the Institute for Marine Mammal Studies, Gulfport, MS. The original document contains color images.