As more pile driving activity occurs, there is an increased concern about its potential effects on fishes and other aquatic organisms. The possibility of effects on fishes rises as more offshore wind farms are installed around the United States and other nations in addition to the ongoing infrastructure and industrial maintenance and development activities, such as those performed by transportation agencies throughout the United States. Effects on fishes potentially associated with pile driving include damage to body tissues that could result in death, as well as impacts on behaviour that could cause fishes to leave sites of biological importance (e.g., feeding, spawning). The goal of this study was to provide quantitative data that may be used to define criterion levels for tissue damage onset and then use these criteria in design of future pile driving projects with options for protection of animals. Regulations for pile driving on the U.S. west coast currently utilize a dual interim criteria approach for onset of physiological effects. These criteria include a cumulative sound exposure level (SELcum) of 187 dB re 1 ?Pa2 s for fishes more than 2 grams and 183 dB re 1 ?Pa2 s for fishes less than 2 grams, and a single-strike peak level (SPLpeak) of 206 dB re 1 ?Pa for all sizes of fishes (Stadler and Woodbury, 2009). If either the SELcum or SPLpeak are exceeded, mitigation protocols should be applied. Field research on effects of pile driving is difficult to execute, and researchers have not had control over the pile driving exposures (frequency of strikes, intensity, duration, and other parameters) nor, in many cases, the physiological state of test fishes during exposure. Thus, it was critical in this study to design an experiment in which researchers had control of all experimental parameters in order to investigate which variables play a role in tissue damage caused by barotrauma. Barotrauma occurs when there is a rapid change in pressure that directly affects the body gases. Free gas in the swim bladder, blood, and tissue of fishes along with gas in solution in blood and other fluids can respectively experience a change in volume and state (e.g. expansion and contraction and/or bubble formation and absorption) during rapid pressure changes, which can lead to tissue damage, organ failure, and changes in behaviour. (Author/publisher) This NCHRP Research Results Digest may be accessed by Internet users at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rrd_363.pdf Appendices A through H can be found on the TRB website at http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=763.
Abstract