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
These studies establish that free-ranging cetaceans 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). Several,
authors, however, suggest that the noise generated by the vessels is probably an important contributing factor to the
responses of cetaceans to the vessels (Blane and Jackson 1994, Evans et al. 1992, 1994), so we may not be able to
treat the effects of vessel traffic as independent of engine and other sounds associated with the vessels.
For surface vessels, the set of variables that help determine whether marine mammals are likely to be disturbed
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).
Below a threshold number of vessels (which probably varies from one species to another, although groups
of marine mammals probably shared sets of patterns), studies have shown that whales will attempt to avoid
an interaction using horizontal avoidance behavior. Above that threshold, studies have shown that marine
mammals will tend to avoid interactions using vertical avoidance behavior, although some marine mammals
will combine horizontal avoidance behavior with vertical avoidance behavior (see Response Analyses for
further discussion);
2. the distance between vessel and marine mammals when the animal perceives that an approach has started
and during the course of the interaction;
3. the vessel’s speed and vector;
4. the predictability of the vessel’s path. That is, whether the vessel stays on a single path or makes continuous
course changes;
6. noise associated with the vessel (particularly engine noise) and the rate at which the engine noise increases
(which the animal may treat as evidence of the vessel’s speed);
7. the type of vessel (displacement versus planing), which marine mammals may be interpret as evidence of a
vessel’s maneuverability.
Because of the number of vessels involved in U.S. Navy training exercises, their speed, their use of course changes
as a tactical measure, and sounds associated with their engines and displacement of water along their bowline, the
available evidence leads us to expect marine mammals to treat Navy vessels as potential stressors. Further, without
considering differences in sound fields associated with any active sonar that is used during these exercises, the
available evidence suggests that major training exercises (for example, RIMPAC, USWEX, and Multiple Strike Group
exercises), unit- and intermediate-level exercises, and RDT&E activities would represent different stress regimes
because of differences in the number of vessels involved, vessel maneuvers, and vessel speeds.
Much of the increase in ambient noise levels in the oceans over the last 50 years has been attributed to increased
shipping, primarily due to the increase in the number and tonnage of ships throughout the world, as well as the
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