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Human Impacts on Marine Mammals

Anthropogenic Noise

Beaked whale strandings with naval sonar

Anthropogenic noise has been recognized as a threat to marine mammals for over 30 years, making noise exposure a central issue for their conservation and management. Noise exposure can lead to direct injury, temporary or permanent hearing loss, and alter important behaviors, such as feeding, resting or reproduction. Some species, such as beaked whales and harbor porpoises, seem to be more vulnerable to negative impacts associated with noise exposure.

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Dr. Anne Simonis spoke with Dr. Chris Parsons about her recent research showing a link between naval exercises and beaked whale strandings in the Marianas Islands. They also talk about ocean soundscapes with the help of some recordings of live whales and dolphins, and how to start a career in marine mammal acoustic research. 

Fishery Interactions

Seal bombs are underwater explosives used in fisheries to deter marine mammals during fishery operations. Pinnipeds are believed to be the primary target for seal bomb use along the US West Coast, however there may be indirect impacts on other species. Our recent mini-review explores potential threats of seal bombs to harbor porpoises around Monterey Bay

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True positive detections of seal bomb explosions in recordings from the MARS cabled observatory ( Circle size represents the number of explosions per hour, for every hour of every day. Times are shown in UTC (Pacific Standard Time is UTC –8 h). Nighttime is shaded. Cumulative histograms are shown by hour and month. Figure reproduced with permission from Ryan (2019).

False killer whales have learned that they can get a 'free meal' by targeting the bait and catch of Hawaiian longline fisheries. This can cause hooking and entanglement of false killer whales, which can lead to serious injuries and death for some individuals. NOAA has formed a Take Reduction Team in order to reduce serious injury and mortality of false killer whales incidental to Hawaiian pelagic longline fisheries. Using acoustic recorders attached to the longline gear, we can learn how and when animals are targeting the fishery in order to design management strategies to reduce negative impacts associated with depredation and bycatch.

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You can learn a lot by listening...

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