Marine Mammal Populations and Ocean Noise: Determining When Noise Causes Biologically Significant Effects

The NRC report contains much valuable information and some important recommendations, but there is some language that is open to misinterpretation. For example, the statement that "[n]o scientific studies have conclusively demonstrated a link between exposure to sound and adverse effects on a marine mammal population" would have more accurately reflected the current state of science if it had been written "there is currently not enough known about marine mammals or the impacts of anthropogenic sound to conclusively demonstrate whether there is or is not a link between exposure to sound and adverse effects on a marine mammal population." While the long-term plan for management of sub-lethal effects proposed in the NRC report is a good one, the suggestions for management in the interim did not always consider cumulative and synergistic effects, the context of exposure (e.g., if a particular animal was more vulnerable, such as a calf), and the impacts of masking (i.e., `drowning out' biologically important sounds, such as communication). The report also failed to address the limitations of relying on self-reporting for observed takes, which even now cannot include unseen mortalities, such as a dolphin that falls loose from a net after it has drowned. A more detailed discussion of the NRC report was published in the Journal of International Wildlife Law and Policy volume 9, pages 91-99 in 2006.