André, M., Degollada, E. Effects of Shipping Noise on Sperm Whale Populations 17 th Annual Conference of the European Cetacean Society , Las Palmas de Gran Canaria, 2003 Resum: Along with the rather recent interest and findings on the cetacean use of sound as an ad-hoc source of energy in the underwater environment, concerns about the effects of environmental degradation and, particularly, the effects of man-made noise on marine mammal conservation, including acoustic pollution, have been mentioned increasingly often. Some direct effects are already notable, such as the increasing mortality rates from shipping collisions with dolphins and whales. From preliminary data in the region of the Canary Islands where resident cetacean populations, particularly sperm whales, are exposed to heavy maritime traffic it is suspected that the local acoustic budget may be influencing the increasing collision rates. Controlled Exposure Experiments (CEE) were conducted to test the feasibility of using an underwater speaker system to prevent collisions and repel sperm whales from ferry routes. None of the low frequency sounds tested were found to have an effect on the whales behaviour. The analysis of the inner ear structures of two sperm whales killed after a collision with a ferry in the Gran Canaria waters showed that there were no fractures or other overt evidence of impact, or ship strike related injuries; however, ears from both animals had reduced auditory nerve volumes. One animal also had patches of dense tissue in the inner ear. These findings confirmed by the histological analysis are consistent with auditory nerve degeneration and fibrous growth in response to low frequency inner ear damage. Although there is no available data on a direct relationship between long-term low frequency sounds exposure from shipping and the increasing collision rate possibly inducing the decline of the local population of sperm whales, the combined results from the CEE and the inner ear structures analysis suggest that low frequency sounds could be considered a marine hearing hazard.