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

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FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 (distance from shore and proximity to one of the areas where humpback whales aggregate), and whether some of these exercises might occur concurrently or concurrent with a major training exercise. If an exercise was conducted in mid-November, the model identified 3 to 9 instances in which humpback whales might be exposed to midfrequency active sonar. If, however, an exercise was conducted during peak densities of humpback whales, the model identified 875 instances in which humpback whales might be exposed to mid-frequency active sonar. We believe the estimates produced by our second and third scenarios are more likely to represent the number of instances in which humpback whale might be exposed to mid-frequency active sonar. The second scenario is more representative because it assumes that humpback whales are most likely to avoid initial or continued exposure to active sonar. The third scenario is representative because it captures patterns of abundance and migration by these whales in waters off the Hawai'ian Islands better than the alternatives. However, both models are sensitive to our assumptions about the rate at which whale densities would change in response to initial or continued exposure and when training activities would actually occur (that is, the scenarios are sensitive to assumptions about whether they would be evenly distributed throughout the year, would occur primarily during periods of low humpback whale density, or during periods of high humpback whale density). Based on the information that is available, we would not expect humpback whales to be exposed to sound fields produced by active sonar associated with all of the training exercises and other activities that would occur in the Hawai'i Range Complex over the next five years. For example, monitoring surveys associated with the November 2007 Undersea Warfare Exercises did not report any sightings of humpback whales while monitoring surveys associated with the March 2008 Undersea Warfare Exercises reported 40 sightings of 68 humpback whales during the exercise. Nevertheless, for the purposes of our analyses and assuming that humpback whales would be exposed to active sonar associated with all training exercises that occur during their tenure in Hawai'i, we would expect each USWEX exercise would result in between 1,682 and 5,448 instances in which humpback whales might be exposed to active sonar (between 8,410 and 27, 240 instances of exposure each year) while the other 32 anti-submarine warfare exercises would result in between 991 and 6,425 instances in which humpback whales might be exposed to active sonar. SEI WHALES. Table 18 summarizes the results of our first scenario, which identifies the number of instances in which sei whales might be exposed to mid-frequency active sonar during exercises the U.S. Navy plans to conduct in the Hawai’i Range Complex each year of the five-year period covered by the proposed MMPA regulations. The second scenario (which assumed that animals would try to avoid continued exposure to active sonar transmissions) identified no instances in which sei whales might be exposed to mid-frequency active sonar at any received level. SPERM WHALES. Table 19 summarizes the results of our first scenario, which identifies the number of instances in which sperm whales might be exposed to mid-frequency active sonar during exercises the U.S. Navy plans to conduct in the Hawai’i Range Complex each year from December 2008 through December 2013. During each of the exercises the U.S. Navy plans to conduct each year from December 2008 through December 2013, the second scenario (which assumed that animals would try to avoid continued exposure to active sonar 184
FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 transmissions) identified 4 instances in which sperm whales might be exposed to mid- frequency active sonar at received levels between 140 and 195 dB. Two to three of those sperm whales would be exposed at received levels between 140 and 150 dB. HAWAI’I MONK SEALS. Table 20 identifies the number of instances in which Hawai’ian monk seals might be exposed to mid-frequency active sonar during exercises the U.S. Navy plans to conduct in the Hawai’i Range Complex each year from December 2008 through December 2013. During future exercises in the Hawai'i Range Complex, the second scenario (which assumed that animals would try to avoid continued exposure to active sonar transmissions) identified no instances in which monk seals would be exposed to mid-frequency active sonar at any received level. Table 18. Estimated number of exposure events in which sei whales might be exposed to mid-frequency active sonar associated with particular exercises the Navy plans to conduct in the Hawai'i Range Complex. Estimates are based on <strong>NMFS</strong>’ first scenario (see text for explanation of scenarios). Estimates for Undersea Warfare Exercises (USWEX) and anti-submarine warfare exercises (ASW) are by event, annual totals are presented in parentheses. The row labeled “(140 – 150 dB)” represents the number of exposure events that might occur at received levels between 140 and 150 dB. Number of Exposure Events Received Level Years with RIMPAC Years without RIMPAC RIMPAC USWEX ASW 1 Total USWEX ASW Total 140 – 195 dB 70 18 (92) 3 (83) 91 (175) 18 (92) 3 (83) 21 (105) (140 – 150 dB) 41 11 (54) 2 (40) 53 (102) 11 (54) 2 (40) 13 (94) 195 – 215 dB 0 0 0 0 0 0 0 > 215 dB 0 0 0 0 0 0 0 Total 70 18 (92) 3 (83) 144 (277) 18 (92) 3 (83) 21 (105) Notes 1 These anti-submarine warfare exercises primarily represent tracing exercises (TRACKEX) and torpedo exercises (TORPEX) Reconciliation of These Estimates The approaches discussed in the preceding narratives were designed to produce different outcomes and their results are not comparable, even if the numbers seem similar. The approach the Navy used in 2006 estimated the number of animals that might accumulate energy equivalent to specific thresholds (for example, temporary or permanent threshold shifts). The approach the Navy used in its most recent NEPA documents for its activities in the Hawai'i Range Complex estimates the proportion of marine mammals that might be “taken” through behavioral harassment (as that term is defined for the purposes of the MMPA) or noise-induced hearing loss as a result of being exposed to active sonar. The approach <strong>NMFS</strong> used estimates the number of instances in which individual animals might be exposed to active sonar at particular received levels in one of three categories (140 to 195 dB, 195 to 215 dB, and greater than 215 dB) regardless of their probable physical, physiological, or behavioral responses to that exposure. Although the estimates produced by the three approaches are not actually comparable (see Table 21 and Table 22), the results also are not necessarily incompatible. It would be possible, for example, for 7,780 sperm whales to be 185
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