NMFS Biological Opinion on U.S. Navy training ... - Govsupport.us

FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013
that might result in reducing the fitness of listed individuals. Ideally, our response analyses consider and weigh
evidence of adverse consequences, beneficial consequences, or the absence of such consequences.
It is important to begin these analyses by stating that, to the best of our knowledge, no data or other information are
available from actual exposures of endangered or threatened marine mammals to mid-frequency active sonar in
either captive or natural settings. We are aware of the studies of the behavioral responses of small cetaceans exposed
to mid-frequency active sonar that are being conducted at the U.S. Navy’s instrumented training range in the
Bahamas (the AUTEC range); however, those studies are still in their infancy and no data from them are available at
the time of this writing. We are also aware of and have cited initial data available from controlled exposure experiments
that are being conducted on killer whales by the Norwegian Defense Ministry; we will incorporate additional
information from those studies as the information becomes available.
Without empirical information on the actual responses of endangered and threatened species to mid-frequency active
sonar, we reviewed the best scientific and commercial data available to assess the probable responses of endangered
and threatened species to mid-frequency active sonar. In the narratives that follow this introduction, we summarize
the best scientific and commercial data on the responses of marine animals to mid-frequency active sonar. Then we
use that information to make inferences about the probable responses of the endangered and threatened marine
animals we are considering in this <strong>Opinion</strong>.
5.3.1 Potential Responses of Listed Species to Vessel Traffic
Numerous studies of interactions between surface vessels and marine mammals have demonstrated that free-ranging
marine mammals engage in avoidance behavior when surface vessels move toward them. It is not clear whether
these responses are caused by the physical presence of a surface vessel, the underwater noise generated by the
vessel, or an interaction between the two (Goodwin and Green 2004; Lusseau 2006). However, several authors
suggest that the noise generated during motion is probably an important factor (Blane and Jackson 1994, Evans et al.
1992, 1994). These studies suggest that the behavioral responses of marine mammals to surface vessels is similar to
their behavioral responses to predators.
As we discussed previously, based on the suite of studies of cetacean behavior to vessel approaches (Au and Green
1990, Au and Perryman 1982, Bain et al. 2006, Bauer 1986, Bejder 1999, 2006a, 2006b; Bryant et al. 1984,
Corkeron 1995, David 2002, Erbé 2000, Félix 2001, Magalhães et al. 2002, Goodwin and Cotton 2004, Hewitt 1985,
Lusseau 2003, 2006; Lusseau and Bejder 2007, Ng and Leung 2003, Nowacek et al. 2001, Richter et al. 2003, 2006;
Scheidat et al. 2004, Simmonds 2005, Watkins 1986, Williams and Ashe 2007, Williams et al. 2002, 2006a, 2006b;
Würsig et al. 1998), the set of variables that help determine whether marine mammals are likely to be disturbed by
surface vessels include:
1. number of vessels. The behavioral repertoire marine mammals have used to avoid interactions with surface
vessels appears to depend on the number of vessels in their perceptual field (the area within which animals
detect acoustic, visual, or other cues) and the animal’s assessment of the risks associated with those vessels
(the primary index of risk is probably vessel proximity relative to the animal’s flight initiation distance).
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