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
nylon with a 45.4 kilogram (100 pound) breaking strength. All parachutes are weighted with a 0.06 kilogram (2
ounce) steel material weight, which would cause the parachute to sink from the surface within about 15 minutes,
although actual sinking rates depend on ocean conditions and the shape of the parachute.
The subsurface assembly descends to a selected depth, and the sonobuoy case falls away and sea anchors deploy to
stabilize the hydrophone (underwater microphone). The operating life of the seawater battery is eight hours, after
which the sonobuoy scuttles itself and sinks to the ocean bottom. For the sonobouys, concentrations of metals
released from batteries were calculated to be 0.0011 mg/L lead, 0.000015mg/L copper, and 0.0000001mg/L silver.
5.2 Exposure Analysis
As discussed in the Approach to the Assessment section of this opinion, our exposure analyses are designed to
determine whether listed resources are likely to co-occur with any direct and indirect beneficial and adverse effects
that these actions have on the environment and the nature of that co-occurrence. In this step of our analyses, we try
to identify the number, age (or life stage), and gender of the individuals that are likely to be exposed to an Action’s
effects and the populations or subpopulations those individuals represent.
Based on the limited empirical information available, we cannot use that information to estimate the number of
endangered or threatened marine animals that might be exposed to the activities the U.S. Navy plans to conduct in
the Hawai’i Range Complex from December 2008 through December 2013. Although Navy watchstanders have
reported the number of large or small cetaceans they observed during some of the exercises that have been conducted
in the Hawai’i Range Complex in the past, those observations do not identify particular species, only represent
individuals that were at the ocean’s surface, and only represent those individuals that might have been sighted given
the sea surface and visibility conditions when the observations were reported. Because marine animals only spend a
portion of their time at the ocean’s surface and because the ability to detect marine animals depends on sea states and
visibility, the number of marine mammals reported by Navy watchstanders would not correspond to the number of
marine animals actually exposed to Navy activities in the Hawai’i Range Complex. Further, the area encompassed
by sound fields produced by activities like active sonar transmissions are so large that it would be almost impossible
to identify or estimate the number of different marine species that are actually be exposed to the sound field, the
received levels associated with the exposure, or changes in the pattern of exposures over the course of an exercise or
test.
As a result, the U.S. Navy, <strong>NMFS</strong>, and most other entities (for example, oil and gas industries for drilling platforms,
geophysics organizations that conduct seismic surveys, etc.) that try to estimate the number of marine animals that
might be exposed to active sound sources in the marine environment rely on computer models, simulations, or some
kind of mathematical algorithm to estimate the number of animals that might be exposed to a sound source. Like all
models, these approaches are based on assumptions and are sensitive to those assumptions.
It is important to note that these simulations tend to over-estimate the number of marine mammals that might be
exposed to one or more of the activities the U.S. Navy plans to conduct in the Hawai'i Range Complex. In most
cases, these over-estimates will be substantial and could imply that marine mammals are continuously exposed to
U.S. Navy training activities in the Hawai'i Range Complex. However, most exposures will be periodic or episodic
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