(b) Effects of Airgun Pulses on Behavior and Movements 162
(c) Possible Impacts of Airgun Sounds 164
(d) Conclusions 166
(e) Literature Cited 166
APPENDIX C: 168
Review of Potential Impacts of Airgun Sounds 168
on Fish 168
(a) Acoustic Capabilities 168
(b) Potential Effects on Fish 170
(c) Literature Cited 176
APPENDIX D: 181
Review of Potential Impacts of Airgun Sounds
on Marine Invertebrates 181
(a) Sound Production 181
(b) Sound Detection 182
(c) Potential Seismic Effects 182
(d) Literature Cited 186
Rice University (Rice), Department of Earth Sciences, plans to conduct a low-energy seismic survey in the Northwest Atlantic Ocean (NWA) during August 2009 with research funding from the National Science Foundation (NSF). The survey will occur along the continental shelf southeast of the island of Martha’s Vineyard (MV), Massachusetts (MA), and will also likely include Nantucket Sound. The survey will take place in water depths ranging from ~20 to ~125 m. The seismic study will use two generator-injector (GI) guns with a total discharge volume of ~90 in3.
NSF, as the funding and action agency, has a mission to “promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense…”. The proposed seismic survey is part of a research proposal recommended for funding by an expert review panel. Vast amounts of freshwater are sequestered under the continental shelf off North America, South America, Europe, and Asia. The proposed survey will provide data integral to advancing a scientific understanding of the distribution and abundance of freshwater available off the U.S. northeast coast, potentially providing a valuable resource to nearby population centers.
Rice is requesting an Incidental Harassment Authorization (IHA) from the National Marine Fisheries Service (NMFS) to authorize the incidental, i.e., not intentional, harassment of small numbers of marine mammals should this occur during the seismic survey. The information in this Environmental Assessment (EA) supports the IHA application process and provides information on additional marine species, including birds, sea turtles, and fish that are listed under the U.S. Endangered Species Act (ESA) and Essential Fish Habitat (EFH). The EA addresses the requirements of the National Environmental Policy Act (NEPA). Alternatives addressed in this EA consist of a corresponding program at a different time, along with issuance of an associated IHA; and the no action alternative, with no IHA and no seismic survey.
Numerous species of cetaceans and pinnipeds inhabit the NWA. Several of these species are listed as endangered under the ESA, including the North Atlantic right, humpback, sei, fin, blue, and sperm whales. Other species of special concern that could occur in the study area are the endangered leatherback and Kemp’s ridley turtles, the threatened loggerhead and green turtles, and the endangered roseate tern. The endangered Atlantic salmon and shortnose sturgeon may also occur at low densities in or near the study area.
Potential impacts of the seismic survey on the environment would be primarily a result of the operation of the two GI guns. A dual-frequency echosounder and a sub-bottom profiler (SBP) will also be operated. Impacts would be associated with increased underwater noise, which may result in avoidance behavior of marine mammals, sea turtles, and fish, and other forms of disturbance. An integral part of the planned survey is a monitoring and mitigation program designed to minimize impacts of the proposed activities on marine animals present during the proposed research, and to document as much as possible the nature and extent of any effects. Injurious impacts to marine mammals and sea turtles have not been proven to occur near airgun arrays, even with higher discharge volumes than that proposed in the present study, and also are not likely to be caused by the other types of sound sources to be used. The planned monitoring and mitigation measures would minimize the possibility of such effects.
Protection measures designed to mitigate the potential environmental impacts to marine mammals and turtles will include the following: ramp ups, a minimum of one dedicated observer maintaining a visual watch during all daytime GI gun operations, 30 min of observations before and during ramp ups during the day and at night, shut downs when marine mammals or sea turtles are detected in or about to enter designated exclusion zones, power downs during turns, shut downs if North Atlantic right whales are sighted at any distance from the source vessel (given their special status), and avoidance of concentrations of sperm, humpback, sei, blue, or fin whales. Rice and its contractors are committed to apply these measures in order to minimize effects on marine mammals and other environmental impacts.
With the planned monitoring and mitigation measures, unavoidable impacts to each species of marine mammal and turtle that could be encountered are expected to be limited to short-term, localized changes in behavior and distribution near the seismic vessel. At most, effects on marine mammals may be interpreted as falling within the U.S. Marine Mammal Protection Act (MMPA) definition of “Level B Harassment” for those species managed by NMFS. No long-term or significant effects are expected on individual marine mammals, sea turtles, or the populations to which they belong, or on their habitats.
The proposed project would have little impact on fish resources. Any effects on EFH would consist of short-term disturbance that could lead to temporary relocation of EFH species or their food. Impacts of seismic sounds on birds are possible, although none are expected to be significant to their populations. Rice will coordinate with recreational and commercial fisheries to minimize the potential for any impacts.