Marine Mammals and Low-Frequency Sound Progress Since 1994 (2000) / Chapter Skim
Currently Skimming:
5 Findings and Recommendations
5 Findings and Recommendations
Pages 73-90
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From page 73... ...
In view of the lack of data for marine mammals exposed to the ATOC signal at received levels above 137 dB, and the incomplete analyses of much of the data collected off the Kauai source, the Committee could reach no conclusions about the effects of the ATOC source at the level of 195 dB. Data from tests of oil industry noises (Malme et al., 1983)
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From page 74... ...
Recommendations: If ATOC does continue, a marine mammal monitoring and research component should be required, but the marine mammal research program should have the flexibility to design and perform playback experiments optimized to yield information about biologically significant effects of the source on marine mammals. In general, any long-term experiment involving high source level ensonification of large areas of the ocean should take precautions to minimize exposure of marine mammals to dangerous levels of sound.
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From page 75... ...
The vessel conducting this photo-identification work could also combine visual and acoustic monitoring of marine mammals and monitor for any unexpected effects of ATOC transmissions with a statistically designed sampling program. In addition, ATOC has a responsibility to design a well-controlled study on the effects of ATOC transmissions on humpback whales within the 130-dB zone around the source.
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From page 76... ...
? This would not be a perfect experiment because it could be argued that baleen whales might not respond the same way as small toothed whales, nor wild animals like captives, but such an experiment should provide insight into the potential behavior of other marine mammals.
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From page 77... ...
This potential problem with acoustic propagation models creates a responsibility for major noise generators to calibrate their model-predicted sound levels against measured levels. Recommendations: With regard to future research to study the effects of humangenerated sound on marine mammals, the Committee supports the recommendation of NRC (1994)
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From page 78... ...
Any research that includes relatively loud sound sources should monitor sound levels around the source site to gather data to calibrate its acoustic propagation models. The locations of ATOC sites were dictated by requirements for the ATOC sound to reach many preplaced receivers and thus were not ideal for observing marine mammals.
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From page 80... ...
Studies of wild marine mammals should include careful determination of their locations, coupled with improved sampling and modeling of acoustic propagation to estimate received sound levels accurately. Alternatively, acoustic data loggers could be mounted on individual animals to record (1)
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From page 81... ...
The ultimate goal of such studies should be to provide information on hearing sensitivity, TTS, nonauditory effects, and other biological parameters listed in Box 5.1 to help in the determination of sound levels that might affect marine mammal hearing or significantly alter their behavior. Physiological methods such as the auditory brainstem response (ABR)
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From page 82... ...
At this time the greatest source of funding for marine mammal research is ONR. However, by its nature, ONR-funded research tends to be focused on questions of practical importance to the Navy and is not necessarily responsive to the broad interests of scientists seeking to learn more about the basic biology of marine mammals.
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From page 83... ...
The agenda for the acoustic oceanographic component of ATOC required different transmission schedules from those that would have been optimal for marine mammal research. For example, the geographic location, depth, and duty cycle (in part)
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From page 84... ...
Future research on marine mammals unquestionably would profit from a broad-based review of the plans developed by multidisciplinary teams and evaluated by a peer-review process that is objective and independent. Such a review should determine whether the proposing investigative teams did the following adequately: · identified basic problems)
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From page 85... ...
are necessary for establishing the baseline of hearing capabilities and normal hearing loss in marine mammals, as also recommended in NRC (1994~. Stranded animals should be assessed to determine if their hearing is "normal." Data are needed to provide comparisons that would allow an evaluation of how common hearing deficits may be among stranded animals.
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From page 86... ...
Such training takes years and is beyond the capabilities or interests of public aquariums. The ocean science community has a variety of different centers and shared-used facilities, for example, the Ocean Drilling Program, that could provide a model for a national captive marine mammal research facility.
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From page 87... ...
Allocation of space, animals, and facility resources should be determined by a broad-based review board on the basis of the quality and significance of the proposed research. An additional virtue of establishing a national captive marine mammal research facility is that the total number of marine mammals removed from the wild would be minimized.
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From page 88... ...
There is a global increase of sound levels in the sea resulting from shipping, recreation, aircraft, and naval operations as well as research (Urick, 1986~. It is important to characterize the existing ambient sound field in terms of the levels, frequencies, and locations of sources, especially in terms of areas particularly important for marine mammals (i.e., the "hotshots" of NRDC, 1999~.
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From page 89... ...
Basic research regarding what is significant about critical habitats and what factors have population-level effects for example, food supply, water quality, and noise levels and characteristics will prove much more effective for protecting marine mammals than merely attempting to regulate individual human activities that may potentially cause changes in the behavior of an individual marine mammal. NMFS regulations should encompass the entirety of noise pollution and other threats to marine mammals.
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