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FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 5.2.2 Exposure to Aircraft Traffic We did not estimate the number of endangered or threatened species that are likely to be exposed to aircraft traffic — during take-offs and landings and at altitudes low enough for the sounds of their flight to be salient below the ocean’s surface — independent of the number of individuals that might be exposed to active sonar associated with those exercises (primarily because the data we would have needed to support those analyses were not available). Nevertheless, we assume that any individuals of the endangered or threatened species that occur in the Action Area during major training exercises (RIMPAC, USWEX, and Multi-Strike) are likely to be exposed to acoustic stimuli associated with aircraft traffic. Many unit-level training exercises and RDT&E activities do not involve aircraft traffic, involve less traffic when they involve traffic at all, have shorter duration, and affect much more localized areas than major exercises, so fewer endangered and threatened species would be exposed to aircraft traffic during these smaller exercises. 5.2.3 Exposure to Mid-Frequency Active Sonar The empirical information available does not allow us to empirically estimate the number of marine mammals that might be exposed to mid-frequency active sonar during the activities that are proposed to occur in the Hawai'i Range Complex that might compare with counts reported by an observer with perfect knowledge of patterns of marine mammal abundance in the Hawai'i Range Complex. The narratives that follow present three different approaches to estimating the number of whales that might interact with sound fields associated with mid-frequency active sonar in the Hawai'i Range Complex: (1) the method the U.S. Navy used to estimate the number of marine mammals that might be “taken” (as that term is defined pursuant to the MMPA) during the 2006 Rim of the Pacific Exercise (which the Navy has not used in subsequent assessments, but which we present for the purposes of continuity with previous <strong>Opinion</strong>s); (2) the method the U.S. Navy and <strong>NMFS</strong>’ Permits Division used in their 2007-2008 Environmental Impact Statement on the Hawai'i Range Complex to estimate the number of marine mammals that might be “taken” (as that term is defined pursuant to the MMPA) during activities the U.S. Navy proposes to conduct in the Hawai'i Range Complex. For marine mammals that are not listed as endangered or threatened, the “take” the Permits Division proposes to authorize using the Letters of Authorization would reflect these “take” estimates (for endangered or threatened marine mammals, “take” estimates would reflect the “take” estimated in the incidental take statements of biological opinions on the permits); and (3) an exposure model <strong>NMFS</strong>’ Endangered Species Division developed using components of an established ecological model (the Hollings’ disc equation) to estimate the number of endangered and threatened marine mammals that are likely to be exposed to active sonar during activities the U.S. Navy proposes to conduct in the Hawai'i Range Complex (the data necessary to estimate the number of sea turtles that might be exposed to active sonar was not available). As discussed in the Approach to the Assessment section of this <strong>Opinion</strong>, these three different approaches represent two different kinds of interactions. The first two approaches cited in this list were designed to estimate the number of times marine mammals might be “taken” (as that term is defined pursuant to the MMPA) as a result of their exposure to active sonar or underwater detonations during training activities while the third approach is designed to estimate the number of times individual animals are likely to be exposed to active sonar, regardess of whether they are “taken” as a result of that exposure. The results of these approaches will be different because, in most cases, the 168
FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 number of animals “taken” by an action would be a subset of the number of animals that are exposed to the action because (1) in some circumstances, animals might not respond to an exposure and (2) some responses may be adverse for an individual animal without constituting a form of “take” (for example, some physiological stress responses only have fitness consequences when they are sustained and would only constitute a “take” as a result of cumulative exposure). As a result, the estimates produced by those approaches are not comparable to the exposure estimates we produce in this <strong>Opinion</strong>. MITIGATION MEASURES TO MINIMIZE THE LIKELIHOOD OF EXPOSURE TO MID-FREQUENCY ACTIVE SONAR. The Navy proposes to implement a suite of mitigation measures to prevent marine mammals from being exposed to mid frequency active sonar at high received levels. As discussed in the Description of the Proposed Action, these measures are centered on safety zones that trigger reductions in maximum transmission levels depending on the proximity of one or more marine mammals to surface vessels, helicopters, and submarines that might be transmitting active sonar or preparing to transmit. These measures rely primarily on Navy watchstanders, helicopter pilots, and other Navy assets detecting marine mammals visually so that the Navy can take the appropriate action. To the degree that the Navy detects marine mammals visually, these safety zones might reduce the number of marine mammals that are exposed to mid-frequency active sonar or the intensity of their exposure. However, the effectiveness of visual monitoring is limited to daylight hours, and its effectiveness declines during poor weather conditions can be very limited (JNCC 2004). In line transect surveys, the range of effective visual sighting (the distance from the ship’s track or the effective strip width) varies with an animal’s size, group size, reliability of conspicuous behaviors (blows), pattern of surfacing behavior, and positions of the observers (which includes the observer’s height above the water surface). For most large baleen whales, effective strip width can be about 3 km (1.6 nm) up through Beaufort 6 (Buckland et al. 1993). For harbor porpoises the effective strip width is about 250 m (273 yd), because they are much smaller and less demonstrative on the surface than baleen whales (Palka 1996). Further, several studies of interactions between seismic surveys and marine mammals and a proposed low-frequency active sonar system and marine mammals concluded that dedicated marine mammal observers were more effective at detecting marine mammals and at detecting marine mammals at greater distances than Navy watchstanders (in these cases, watchstanders of the Navies of other countries, who may not have training that is comparable to U.S. Navy watchstanders), were better at identifying the marine mammal to species, and reported a broader range of behaviors than other personnel (Aicken et al. 2005; Stone 2000, 2001, 2003). It is not clear, however, how the U.S. Navy’s watchstanders and lookouts, who are specifically trained to identify objects in the water surrounding Navy vessels compare with observers who are specifically trained to detect and identify marine mammals. <strong>NMFS</strong> is working with the Navy to assess the effectiveness of Navy watchstanders and the degree to which they are likely to minimize the probability of exposing marine mammals to mid-frequency active sonar. A multi-year study conducted on behalf of the United Kingdom’s Ministry of Defense (Aicken et al. 2005) concluded that Big Eye binoculars were not helpful. Based on these studies, we would conclude that requiring surface vessels equipped with mid-frequency active sonar to have Big Eye binoculars in good working order might not increase the number of marine mammals detected at distances sufficient to avoid exposing them to received levels that might result in adverse consequences. 169
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