Marine Mammal Populations and Ocean Noise Determining When Noise Causes Biologically Significant Effects (2005) / Chapter Skim
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Executive Summary
Executive Summary
Pages 1-12
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At some point as humans introduce more sound into the oceans, the conflict with evolutionarily-adapted marine mammal sound-sensing systems seems inevitable. Attention has been drawn to this issue through a series of marine mammal strandings, lawsuits, legislative hearings, and National Research Council (NRC)
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The 1994 amendments introduced two levels of takes by harassment under the MMPA -- level A and level B harassment. Level A harassment was defined in the 1994 amendments as "any act of pursuit, torment, or annoyance which has the potential to injure a marine mammal or marine mammal stock in the wild." Level B harassment was defined as "any act of pursuit, torment, or annoyance which has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering." However, the 2000 National Research Council report emphasized the importance of a criterion for significance of disruption of behavior (pg.
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) , so the primary BOX ES-1 Statement of Task In its 2000 report, Marine Mammals and Low-frequency Sound, the National Research Council recommended that the Marine Mammal Protection Act definition of "Level B harassment should be limited to meaningful disruption of biologically significant activities that could affect demographically important variables such as reproduction and longevity." Recognizing that the term "biologically significant" is increasingly used in resource management and conservation plans, this study will further describe the scientific basis of the term in the context of marine mammal conservation and management related to ocean noise.
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A transfer function is essentially a relationship that allows one to estimate, for example, how a change in migration route leads to a reduction in reproductive success. It was quickly recognized that the high-priority research identified in the earlier National Research Council reports (1994, 2000, 2003b)
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To enhance such a model and progress toward determining population effects of acoustic disturbance, all available sources of data on marine mammal behavior and reactions to noise will need to be accessed. In addition to results of normal scientific studies, a veritable wealth of data on marine mammals is collected in compliance with federal regulatory requirements, but those data are not being accessed or used beyond the original intent of their collection (such as for permit issuance)
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For animals in which blood sampling is impractical, fecal sampling has been used successfully and is now being applied to some marine mammals. Preliminary studies measuring glucocorticoids in hair samples and enhanced synthesis of RNA coding for stress-induced proteins in skin samples merit further development.
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One approach involves demographic models in which age- or stagespecific developmental, behavioral, or physiological characteristics of individuals are used to explore changes in population dynamics (Caswell,
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For a number of nonmarine mammal species, individual-based models include physiology and behavior; such models have provided insight into how ecological change and human disturbance have altered demographic variables. Although a thorough, detailed model is not now possible for any marine mammal species, this approach can be used to provide preliminary understanding and to identify the most crucial gaps in available data.
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RECOMMENDATION 6: A practical process should be developed to help in assessing the likelihood that specific acoustic sources will have adverse effects on a marine mammal population by disrupting normal behavioral patterns. Such a process should have characteristics similar to the Potential Biological Removal model, including · Accuracy, · Encouragement of precautionary management -- that is more conservative (smaller removal allowed)
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The predictive model and even the proposed revisions to PBR will take years to implement. In the interim, those who introduce sound into the marine environment and those who have responsibility for regulating sound sources need a system whereby reasonable criteria can be set to determine whether a particular sound source will have a nonsignificant effect on marine mammal populations.
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The goal of this report is to provide a method for clarification of the concept of biologically significant disturbance.The recommendations made here are intended to provide both a long-term, well-supported, and valid solution and a near-term problem-solving strategy to assist resource managers in coping with this difficult and complex issue.
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