The purpose of this report is to describe what is known about the effects of sound (including those from pile driving activities) on fishes and to identify studies needed to address areas of uncertainty relative to measurement of sound and the response of fishes. Exposure to sound is defined to include both the received level and duration of the signal.
The emphasis of this report is on the known effects of sound received by fishes. The effects are known if both the received sound and its elicited effect are well defined. Detailed source characteristics of various types of piles and detailed analyses of the effectiveness of various sound attenuation technologies (e.g., bubble curtains) are beyond the scope of this report.
The results in the peer-reviewed and gray literature on the effects of sound on fishes are variable and, as yet, give no clear-cut “rules” as to what sounds will affect fish and how they will be affected. A limited number of quantitative and qualitative studies and observations show mortality related to pile driving and also provide some data pertaining to the effects of sound on fishes. Results based on sound signals other than pile driving indicate that some exposures to sound will cause a change in the hearing capabilities of some test fish species or actually damage the sensory structures of the inner ear. There is also a very limited body of evidence that leads to the suggestion that exposure to sound has the potential for affecting other aspects of the physiology of fish, and that these effects may range from the macro (destruction of the swim bladder) to the cellular and molecular.
Data from explosive blast studies, while not directly com parable to pile driving, indicate that very fast, high-level acoustic exposures can cause physical damage and/or mortally wound fishes. There is also reason to believe that lesser effects might also occur, but these have not been well documented. Just as in investigations testing the effects of sound, however, the number of species studied in tests of the effects of explosives is very limited, and there have been no investigations to determine whether blasts that do not kill fish have had any impact on short- or long-term hearing loss, or on other aspects of physiology (e.g., cell membrane permeability, metabolic rate, stress), and/or behavior (e.g., feeding or reproductive behavior, movement from preferred home sites).
While these earlier studies provide a preliminary indication of the potential impact of pile driving on fishes, there are no peer-reviewed studies that examine the effects of pile driving on fish hearing, and there are only a few non-peer-reviewed reports about effects on non-sensory structures. 2 While we are able to use available data as a very preliminary indication of the kinds of effects that might be encountered as a result of pile driving, only additional well-controlled studies of behavioral and physiological responses to pile driving or to signals specifically designed to have the same acoustic characteristics as pile driving sounds, will provide clear scientific support of any criteria that are to be established.