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OCR for page 103
B Summary from NRC [1 994)
LIMITATIONS OF CURRENT KNOWLEDGE
Data on the effects of low-frequency sounds on marine mammals are scarce.
Although we do have some knowledge about the behavior and reactions of
certain marine mammals in response to sound, as well as about the hearing
capabilities of a few species, the data are extremely limited and cannot con-
stitute the basis for informed prediction or evaluation of the effects of intense
low-frequency sounds on any marine species.
The committee could find almost no quantitative information with which to
assess the impact of low-frequency noise on marine mammals. For those few
marine mammals on which data are available about their hearing sensitivity, it
appears that low-frequency sound, even at very high levels, is barely audible to
them. In addition, the range of frequencies by which these animals are affected
appears to vary among, as well as within, the three different orders of Mammalia
to which they belong. Certainly data on the hearing sensitivities of several
Odontoceti (examples include the white whale, bottlenose dolphin, harbor por-
poise, and false killer whale) and Pinnipedia (for example, several seals and the
California sea lion) suggest that sounds below about 100 Hz are practically
inaudible to these mammals. But even these data are extremely limited and
cannot be used to evaluate the effects of intense low-frequency sounds on all
species of marine mammals.
There have been some observational or experimental studies and numerous
anecdotal reports about the responses of marine mammals to certain sounds.
Rather than summarize the existing reviews, the committee decided that its efforts
103
OCR for page 104
104
APPENDIX B
could be more usefully directed to a discussion of the implications of the existing
information. The committee noted, for example, that missing in most of these
anecdotal accounts is information on the level of the sound exposure experienced
by individual animals. Typically, neither the source level nor the received level
was measured. Even when the approximate level at the source was known, the
received level near the animal was usually not measured, and if it was, there were
often uncertainties associated with calculating that level.
This dearth of scientific evidence makes it virtually impossible to predict the
effects of low-frequency sound on marine mammals, especially on baleen whales.
In the absence of such an impact assessment, the committee finds itself unable to
fulfill the second part of its charge, namely, to balance the costs and the benefits
of "underwater sound as a research tool" versus "the possibility of harmful ef-
fects to marine mammals." Rigorous experimental research on marine mammals
and their major prey is required to resolve the issue of how low-frequency sound
affects these species. The committee recommends that future experiments be
conducted in such a manner that the received level of the sound and the behavior
of the animal can be studied together. Such investigations may be logistically
complex and may require permits, which are sometimes difficult to obtain.
CHANGES PROPOSED IN REGULATORY STRUCTURE
It is the committee's judgment that the regulatory system governing marine
mammal "taking" by research actively discourages and delays the acquisi-
tion of scientific knowledge that would benefit conservation of marine mam-
mals, their food sources, and their ecosystems. The committee thus proposes
several alternatives for reducing unnecessary regulatory barriers and
facilitating valuable research while maintaining all necessary protection for
marine mammals.
Although the committee strongly agrees with and supports the objective of
marine mammal conservation, it believes that the present regulation of research is
unnecessarily cumbersome and restrictive. Not only is research hampered, but
the process of training and employing scientists with suitable research skills is
impeded by this system. Better and more humane management of marine mam-
mals depends on understanding them better. Well-trained researchers are the
ultimate source of our knowledge about marine mammals. The present system,
in effect, impedes acquisition of the information and understanding needed to
pursue a more effective conservation policy.
The committee considered several possible alternatives for facilitating valu-
able research while maintaining all necessary protection for marine mammals.
One alternative would be to incorporate scientific researchers as "other users" in
the regulatory regime recently proposed by the National Marine Fisheries Service
(NMFS) of the U.S. Department of Commerce to govern commercial fishing and
OCR for page 105
APPENDIX B
105
marine mammal interactions. Another alternative would be to establish a decen-
tralized regulatory regime, possibly patterned after the Institutional Animal Care
and Use Committee (IACUC) system currently used to monitor research con-
ducted on nonmarine animals in scientific laboratories.
If the existing system of regulations is maintained, the committee urges that
steps be taken to expedite the small incidental take authorization process for all
scientific activities involving nonlethal takes, and to further simplify the process
for nonlethal takes producing only negligible impact. The committee suggests
rewording those provisions to delete references to effects on "small" numbers of
marine mammals, provided that the effects are negligible. It would also be
beneficial to broaden the definition of research for which scientific permits can
be issued to include activities beyond those directly "on or benefiting marine
mammals." In order to place regulations on a more rational footing, the popula-
tion status of each species should determine the number and types of allowable
takes, and the same regulations should apply equally to all activities, scientific
and otherwise. The committee notes that some of these recommendations would
require congressional action to change the Marine Mammal Protection Act and
perhaps other laws. However, other recommendations could be implemented
under existing laws through changes in regulations.
The committee is by no means recommending a blanket waiver of the require-
ments for scientific research under the Marine Mammal Protection Act, the
Endangered Species Act, and the National Environmental Policy Act whether
on marine mammals or on other topics where experiments might incidentally
affect marine mammals. Rather, the committee urges a more logical balance
between the regulation of research and other human activities, and a more expe-
ditious permitting process. Appropriate scientific research might identify the
sources of human-made noise that actually endanger marine mammals, and may
suggest regulation of certain sound sources that are presently unregulated. This
research could provide information that would benefit all marine mammals.
Finally, the committee considered the "120-decibel (dB) criterion" that is
regarded in some contexts as a noise level above which potentially harmful
acoustic effects on marine mammals might occur. In the opinion of the com-
mittee, the data from which the 120-dB criterion was derived are being overly
extrapolated, largely because of the scarcity of experiments providing quantita-
tive information about the behavior of marine mammals in relation to sound
exposure. It is possible that this level is simply the one at which the animals
detected the presence of a sound. If this is true, then there is no scientific
evidence to indicate that the relatively minor and short-term behavioral reactions
observed indicate any significant or long-term effects on the animals. Marine
mammals, like other animals, respond to many stimuli, natural and human-made.
These reactions are part of their normal behavioral repertoire and are not neces-
sarily indicative of an adverse effect.
One danger of adopting a single number, as with the 120-dB criterion, is in
OCR for page 106
106
APPENDIX B
applying it to all species of marine mammals and to all sounds and situations,
regardless of the frequency spectrum, regardless of the temporal pattern of the
sound, and regardless of differences in the auditory sensitivity of the different
groups of marine mammals. There is general agreement that these variables are
important in determining whether the 120-dB figure is appropriate in any given
situation.
RECOMMENDED RESEARCH
The research that would provide some of the missing information is concep-
tually straightforward biological science, the proposed experiments should
provide much of the needed information, and the cost is not enormous com-
pared with that of other scientific efforts of comparable magnitude.
The committee's aim was to identify general research needs that are crucial
to a full evaluation of the effects of intense low-frequency sounds on a variety of
marine mammals and their major prey. The committee has identified the follow-
ing general areas in which more information must be developed:
1. Research on the behavior of marine mammals in the wild.
2. Research on the auditory systems of marine mammals.
3. Research on the effects of low-frequency sound on the food chain of
marine mammals.
4. Development and application of measurement techniques to enhance
observation and data gathering.
The committee recommends that an accelerated program of scientific studies
of the acoustic effects on marine mammals and their major prey be undertaken.
These studies should be designed to provide information needed to direct policies
that will provide long-term protection to the species.
Representative terms from entire chapter:
major prey
