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r Executive Summary Sound has become a major tool for studying the ocean. Although the ocean is relatively opaque to light, it is relatively transparent to sound. Sound having frequencies below 1,000 Hertz (Hz) is often defined as low-frequency sound. The speed of sound is proportional to the temperature of the water through which it passes. Therefore, sound speed can be used to infer the average temperature of the water volume through which sound waves have passed. The relationship between water temperature and the speed of sound is the basis for the Acoustic Thermometry of Ocean Climate (ATOC) experiment. The ATOC experiment is designed to monitor the travel time of sound between sources off the coasts of Hawaii and California and several receivers around the Pacific Ocean in order to detect trends in ocean temperature and for other research and monitoring pur- poses (ATOC Consortium, 1998~. The ATOC transmissions are centered at a frequency of 75 Hz, with peak source levels of 180 decibels (dB) re 1 pPa @ lm1 at this frequency and 195 dB for its broadband source level. Based on well-tested models of signal loss over distance in deep water, the source level should decrease to 155 dB within 100 m from the source and to 135 dB at 1 km from the source. Some whales, seals, and fish use low-frequency sound to communicate and to sense their environments. For example, baleen whales and some toothed whales are known to use and respond to low-frequency sound emitted by other 1 Decibels are used to describe the ratio between two quantities, in this case, the ratio of the sound pressure level (SPL) of the source to the SPL of 1 microPascal (,uPa) at one meter from the source. "re" = "with reference to." The report will henceforth omit the "re 1 pPa @ lm" notation when referring to decibel levels measured in water. Measurements made in air are referenced to 20 pPa @ 1 m and will be identified in the text. 1

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2 MARINE MAMMALS AND LOW-FREQUENCY SOUND individuals of their species. Sharks are not known to produce low-frequency sound but are attracted to pulsed low-frequency sounds. Therefore, it is possible that human-generated low-frequency sound could interfere with the natural behavior of whales, sharks, and some other marine animals. In 1994 the Defense Advanced Research Projects Agency (DARPA) requested that the National Research Council (NRC) convene a committee to evaluate the results of ATOC's Marine Mammal Research Program (MMRP) (see Appendix A for Committee biographies). The MMRP was designed to monitor the effects of ATOC transmissions on marine mammals. Although DARPA was the original sponsor, the Office of Naval Research (ONR) is now funding the MMRP and cosponsored this study. The NRC was asked to conduct an updated review of Low-Frequency Sound and Marine Mam- mals: Current Knowledge and Research Needs (NRC, 1994), based on data obtained from the MMRP and results of any other relevant research, including ONR's research program in low-frequency sound and marine mammals; 2. compare new data with the research needs specified in the 1994 NRC report, focusing on the strengths and weaknesses of the data for answering the important outstanding questions about marine mammal responses to low- frequency sound; and 3. identify areas where gaps in our knowledge continue to exist. The Committee reviewed numerous written documents and was briefed on the MMRP's progress at the program's midpoint (in 1996) and about 6 months after the completion of its field observations (in 1999~. The NRC was asked to prepare an interim report to provide midproject guidance to the MMRP as well as this final report. Some of the recommendations in the interim report (NRC, 1996) were implemented by 1999, but for a variety of reasons others were not. For its update of research priorities related to marine mammals and low- frequency sound, the Committee augmented the MMRP results with results from the scientific literature, ONR's program on marine mammals, and observations of the reactions of marine mammals to tests of the Navy's low-frequency active (LFA) sonar. This report does not examine the effects of all human-generated sound (only low-frequency sound is considered), nor does it include all marine mammals (only whales and seals are included). This report updates all aspects of NRC (1994), including the issue of acoustic harassment and its regulatory defini- tion in light of the 1994 reauthorization of the Marine Mammal Protection Act (MMPA). The publication of the report is particularly timely because the MMPA expired on October 1, 1999 and is in the process of being reauthorized. The Committee focused exclusively on whales and seals, because (1) they are found near the ATOC sources, (2) the effects of low-frequency sound on whales and seals have been studied to a greater extent than effects on other marine mammals (in part, because they live near ATOC sources), and (3) it is thought that low-

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EXECUTIVE SUMMARY 3 frequency sound is less likely to have a significant impact on other marine mammals, including sea and marine otters, manatees and dugongs, and polar bears. FINDINGS AND RECOMMENDATIONS Some of the MMRP observations, such as movements of humpback whales in near-coastal areas off Kauai and the abundance of some whale species near the Pioneer Seamount source off California, showed no statistically significant effects of ATOC transmissions. For these observations, the Committee could not distin- guish among true lack of effect and insufficient observations, small sample sizes, and incorrect statistical treatment of data. A somewhat clearer lack of significant effects of the ATOC transmissions was demonstrated in observations of elephant seals' diving behavior near the Pioneer Seamount source. Some statistically significant differences between control and exposure conditions were found for other species, including (1) an increase in average distance of humpback whales from the California source and (2) increased dive duration for humpback whales off Hawaii. The MMRP found no obvious catastrophic short-term effects as a result of transmissions from either source, such as mass strandings or mass deser- tions of source areas. Statements about whether ATOC should be allowed to continue, based on MMRP and other results, are clearly outside the Committee' s statement of task. However, the Committee does offer suggestions about how future large-scale acoustic tomography experiments could be designed to accomplish appropriate monitoring for scientific purposes and mitigation measures to decrease the possi- bility of harm to marine mammals. Progress has been made since 1994 in answering several of the research questions described in the 1994 NRC report. Research funded by ONR and other agencies and the results of the MMRP and LEA tests have contributed new knowledge regarding the effects of low-frequency sound on marine mammals. Research and observations published since 1994 have extended our knowledge of the hearing abilities of marine mammals at lower frequencies, at depth, in the presence of human-generated noise, and among different individuals of the same species. More observations of baleen whale vocalizations and responses to sound have been collected and a greater appreciation has been gained about how the respective locations of a baleen whale and a sound source can affect vocalizations and other behavior. Extensive testing with conventional and new methods, such as computational modeling of ear anatomy, auditory evoked potential techniques, and stimulus-response experiments with trained animals have provided new insights into normal hearing and the levels of sound required to produce shifts in the hearing abilities of individual animals. Most of the research directions recommended by the 1994 report are still relevant. This continued need to answer the questions raised therein is not due to

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4 MARINE MAMMALS AND LOW-FREQUENCY SOUND lack of effort but is a result of the complexities of the questions and the difficul- ties of conducting studies on marine mammals because of the lack of adequate research support, equipment, techniques, and facilities. . The 1994 amendments to the MMPA (16 U.S.C. 1361 et seq.) changed the legal definitions of marine mammal "harassment" as applied to scientific use of sound in the ocean. If the MMPA is to be implemented responsibly, however, additional changes should be made to the act and to the regulations promulgated pursuant to the act by the Office of Protected Resources of the National Marine Fisheries Service (NMFS) in the National Oceanic and Atmospheric Administra- tion (NOAA). There is little disagreement that scientific use of sound in the ocean is a minor component of human-generated sound pollution. Industry (e.g., shipping and hydrocarbon exploration and production) are thought to be the largest sources. Yet, uses of sound by scientists and the Navy are the most stringently regulated. Unfortunately, few data are available to regulators regarding ambient noise levels in the ocean and the relative importance of different sources in contributing to the cumulative human-generated noise. Cooperative funding of research by govern- ment and industries responsible for the noise could result in more rapid advance of knowledge about the effects of sound on marine mammals and cooperative solutions to noise problems. This report includes a number of recommendations to Congress, to NOAA in its regulatory role, and to research sponsors, as well as to the scientific commu- nity. The recommendations directed to Congress should be implemented in the upcoming reauthorization of the MMPA. The recommendations directed to NOAA in its regulatory role should be implemented as it promulgates new regu- lations based on the reauthorized MMPA. Finally, agencies that fund marine mammal and acoustic research should begin weighing recommendations about research, monitoring, and facilities against other budget priorities for the fiscal year 2002 budget cycle and beyond. Some of the recommendations to research sponsors should not require reprogramming or new money and could be imple- mented immediately. Recommendations for Congress As part of the upcoming reauthorization, Congress should consider changes to the MMPA that would allow studies of the ocean while protecting marine mammals. In particular, Congress should consider the following actions: define "type B harassment" of marine mammals in terms of significant disruption of behaviors critical to survival and reproduction. acknowledge the relative significance of different sources of sound in the ocean, insofar as this is known, and provide new means to bring all commercial sources of sound into the MMPA's legal and regulatory framework.

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EXECUTIVE SUMMARY s The committee believes that regulation of sound in the ocean is based on inadequate information and that more information needs to be collected. Congress should decide what kinds of regulations are appropriate and how much funding should be available for marine mammal research, given the existing inadequacy of knowledge. Recommendations for NOAA NOAA' s responsibilities with respect to whales and seals are set forth in the MMPA, the Endangered Species Act, and other relevant legislation. NOAA's responsibility has been delegated to NMFS. Although NMFS conducts and supports some marine mammal research, it has conducted or supported very little research aimed at determining the potential effects of anthropogenic sound on the distributions, sizes, or productivity of marine mammal species or stocks. In September 1998, NMFS held a workshop to seek input from the scientific com- munity regarding guidelines or regulations that might be promulgated to guide or govern authorization of the taking of marine mammals incidental to activities that use or produce sound in the ocean (no publication resulted from the meeting). The workshop participants noted a variety of uncertainties concerning the pos- sible effects of anthropogenic sound on marine mammals. Pending resolution of the uncertainties, NMFS should focus on developing and evaluating the effec- tiveness of guidelines for preventing injuries and disruption of behavior that could affect survival or reproduction. NMFS should consult further with experts in oceanography, bioacoustics, underwater sound propagation, and animal be- havior to (1) identify sound-producing activities that, because of their nature, location, intensity, or duration, are likely to have biologically significant effects on marine mammals and thus should be higher priority for enforcement of the "taking" authorization under the MMPA or the Endangered Species Act; and (2) for cases in which there is uncertainty or disagreement as to possible adverse effects of underwater sound on survival or productivity, describe (a) the research required to resolve the uncertainty, and/or (b) the monitoring that should be required as a condition of any incidental take authorization provided by NMFS. Further, NMFS should work cooperatively with ONR to develop technology and programs for monitoring ambient sound levels and noise pollution in critical marine mammal habitats and to develop and implement methods for obtaining data on the hearing capabilities of marine mammals, including data on auditory sensitivity, damage thresholds, and potential for behavioral disruptions of repre- sentatives of all types of marine mammals (see Box 5.1~. Recommendations for Research Sponsors Developing an understanding of the effects of low-frequency sound on marine mammals will require a more sustained and integrated approach than has

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6 MARINE MAMMALS AND LOW-FREQUENCY SOUND been the case in previous research. Much research in the past was conducted by single investigators responding to the need for specific information about the effects of a single sound source. Multi-investigator teams of biologists, acousti- cians, psychoacousticians, engineers, and statisticians should be funded to con- duct a set of systematic studies of marine mammal species that represent different potential hearing abilities, based on the need to know how sound of different types affects characteristic species. The committee also identifies the need for research to determine: now marine mammals utilize natural sound for communication and for maintaining their normal behavioral repertoires; . the responses of free-ranging marine mammals to human-generated acous- tic stimuli, including repeated exposure of the same individuals to the same stimulus; the response of deep-diving marine mammals to low-frequency sounds whose characteristics duplicate or approximate those produced by acoustic ocean- ographers and other sources of human-generated sound, such as low-frequency military sonars and sounds used for seismic exploration; basic hearing capabilities of various species of marine mammals; hearing capabilities of larger marine mammals that are not amenable to laboratory study; audiometric data on multiple animals of different sexes and ages in order to understand variance in hearing capabilities within a given species; sound pressure levels that produce temporary and permanent hearing loss . . In marine mammals; condition of a representative sample of important cochlear structures in different species of wild marine mammals using post-mortem examinations; morphology and sound conduction paths of the auditory system in various marine mammals; . temporal-resolving power for various marine mammals; whether low-frequency sounds affect the behavior and physiology of organisms that serve as part of the food chain for marine mammals; and whether low-frequency sounds affect the nonauditory physiology or struc- tures of marine mammals. Such research should be sponsored by the agencies that fund basic and applied biological research and that fund ocean research using sound, including ONR, NOAA, the National Science Foundation (NSF), the Minerals Manage- ment Service, the Biological Resources Division of the U.S. Geological Survey, and the National Institutes of Health (NIH). Mission-oriented agencies should ensure that the research they sponsor will not only contribute to their immediate missions but also answer basic questions about marine mammal bioacoustics. Agencies that fund more fundamental science, such as NSF and NIH, should

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EXECUTIVE SUMMARY 7 consider funding marine mammal research when it has implications for under- standing basic biology or health-related issues. Most importantly, all of these projects should receive strict peer review and be evaluated on the quality of the science proposed. Other generators of sound in the ocean, such as shipping and hydrocarbon exploration and production companies, also should participate in funding research on the effects of sound on marine mammals. Given our ignorance about safe exposure levels of sound, great benefit could accrue if ocean noise generators, government agencies, and environmental groups formed a consortium to fund the kinds of research recommended in this report. Opportunities may also exist for cooperation between U.S. scientists and agencies and their counterparts in other nations. Cooperation with Canada and Mexico could be particularly productive because several species cross the exclusive economic zones of the three nations. For example, another NRC (1999) report described research on marine mammals that could benefit from binational research by the United States and Mexico. Europe is also a likely source of partners for cooperative research and manage- ment, given the shared marine mammal stocks and the existing cooperation in the North Atlantic Treaty Organization, which shares both active and passive sonar sources with the United States. A variety of organizations, including the Ocean Drilling Program, provide models for the possible structure and functioning of a multinational consortium for research on the effects of sound on marine mammals. Research on captive marine mammals is expensive because of the need for extended training and maintenance of animals and the added requirement of highly specialized care (e.g., aquatic veterinarians). Funds to support marine mammals must be provided for the long term because once an animal is in captivity it generally must be maintained there for its lifetime. Facilities to conduct research with marine mammals are difficult to set up, and most existing commercial facilities are not able to provide access to animals for research. However, without such facilities, many basic science studies on marine mammal bioacoustics (and other aspects of marine mammal biology) such as those described in this report cannot be conducted, and it will be difficult to develop regulations that protect marine mammals appropriately. The lack of a specialized marine mammal research facility available to U.S. scientists has hindered the progress of research on marine mammal hearing. If the studies described in this report are of sufficient priority to reduce uncertainties in the regulation of human- generated sound in the ocean, federal agencies should consider establishing a national facility for the study of marine mammal hearing and behavior. If estab- lished, the proposed facility should be made available to the entire scientific community, and the allocation of animal experimental and observation time should be based on the scientific merit of proposals as determined by peer- reviewed evaluation of research. Funding for research at this facility should be coordinated with the availability of animals to ensure that once an investigator receives funding he or she will have access to appropriate animals. The committee

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8 MARINE MAMMALS AND LOW-FREQUENCY SOUND believes that such a facility could be established at relatively little incremental cost by enhancement of an existing facility. Our understanding of how marine mammals react to natural and human- made sound is rudimentary. The actions recommended in this report could result in significant advances in knowledge and better regulation of human activities that might be harmful to marine mammals.