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 substantially over-estimate the actual number of exposure events. For species like sei whales, which only occur in the Hawai'i Range Complex in small numbers, an estimate of 175 exposures is probably a substantial over-estimate of the actual exposure even if it represents the best estimate available. As discussed in the Status of the Species section of this opinion, we have no specific information on the sounds produced by sei whales or their sensitivity to sounds in their environment. Based on their anatomical and physiological similarities to both blue and fin whales, we assume that the hearing thresholds of sei whales will be similar as well and will be centered on low-frequencies in the 10-200 Hz. This information would lead us to conclude that, like blue and fin whales, sei whales exposed to these received levels of active mid-frequency sonar are not likely to respond if they are exposed to mid-frequency (1 kHz–10 kHz) sounds. Like fin whales, sei whales in the action area seem likely to respond to the ship traffic associated with each of the activities the U.S. Navy plans to conduct in the Hawai'i Range Complex in ways that approximate their responses to whale watch vessels. As discussed in the Environmental Baseline section of this <strong>Opinion</strong>, those responses are likely to depend on the distance of a whale from a vessel, vessel speed, vessel direction, vessel noise, and the number of vessels involved in a particular maneuver. Sei whales also seem most likely to try to avoid being exposed to the activities and their avoidance response is likely to increase as an exercise progresses. We do not have the information necessary to determine which of the many sounds associated with an exercise is likely to trigger avoidance behavior in sei whales (for example, engine noise, helicopter rotors, ordnance discharges, explosions, or some combination of these) or whether fin whales would avoid being exposed to specific received levels, the entire sound field associated with an exercise, or the general area in which an exercise would occur. Particular whales’ might not respond to the vessels, while in other circumstances, sei whales are likely to change their vocalizations, surface time, swimming speed, swimming angle or direction, respiration rates, dive times, feeding behavior, and social interactions (Amaral and Carlson 2005; Au and Green 2000, Cockeron 1995, Erbe 2002, Félix 2001, Magalhães et al. 2002, Richter et al. 2003, Scheidat et al. 2004, Simmonds 2005, Watkins 1986, Williams et al. 2002). Some of these whales might experience physiologyical stress (but not “distress”) responses if they attempt to avoid one ship and encounter a second ship during that attempt. However, because of the relatively short duration of the different exercises and the small number of times the exercises are likely to be repeated from December 2008 to December 2013, we do not expect these responses of sei whales to reduce the fitness of the sei whales that occur in the Hawai'i Range Complex. Based on the evidence available, we conclude that training exercises and other activities the U.S. Navy plans to conduct in the Hawai'i Range Complex each year from December 2008 through December 2013 are not likely to adversely affect the population dynamics, behavioral ecology, and social dynamics of individual sei whales in ways or to a degree that would reduce their fitness. As we discussed in the Approach to the Assessment section of this opinion, an action that is not likely to reduce the fitness of individual whales would not be likely to reduce the viability of the populations those individual whales represent (that is, we would not expect reductions in the reproduction, numbers, or distribution of those populations). As a result, the activities the U.S. Navy plans to conduct in the Hawai'i Range Complex from December 2008 to December 2013 would not be expected to appreciably reduce the sei whales’ likelihood of surviving and recovering in the wild. 246
FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 SPERM WHALES. During future Rim of the Pacific Exercises, the first scenario (which assumed that animals would not move) identified 1,952 instances in which sperm whales might be exposed to mid-frequency active sonar at received levels between 140 and 195 dB, five instances in which sperm whales might be exposed at received levels between 195 and 215 dB, and one instance in which sperm whales might be exposed at received levels greater than 215 dB. During the other anti-submarine exercises (USWEX, TRACKEX, and TORPEX) the U.S. Navy plans to conduct in the Hawai’i Range Complex each year, the first scenario identified another 587 instances in which sperm whales might be exposed to mid-frequency active sonar transmissions at received levels between 140 and 195 dB, 1 instance in which sperm whales might be exposed at received levels between 195 and 215 dB, and one instance in which sperm whales might be exposed at received levels greater than 215 dB over the five-year period of the proposed regulations. If exposed to mid-frequency sonar transmissions, sperm whales are likely to hear and respond to those transmissions. The only data on the hearing range of sperm whales are evoked potentials from a stranded neonate (Carder and Ridgway 1990). These data suggest that neonatal sperm whales respond to sounds from 2.5-60 kHz. Sperm whales also produce loud broad-band clicks from about 0.1 to 20 kHz (Weilgart and Whitehead 1993, 1997; Goold and Jones 1995). These have source levels estimated at 171 dB re 1 μPa (Levenson 1974). Current evidence suggests that the disproportionately large head of the sperm whale is an adaptation to produce these vocalizations (Norris and Harvey 1972; Cranford 1992; but see Clarke 1979). This suggests that the production of these loud low frequency clicks is extremely important to the survival of individual sperm whales. The function of these vocalizations is relatively well-studied (Weilgart and Whitehead 1993, 1997; Goold and Jones 1995). Long series of monotonous regularly spaced clicks are associated with feeding and are thought to be produced for echolocation. Distinctive, short, patterned series of clicks, called codas, are associated with social behavior and interactions within social groups (Weilgart and Whitehead 1993). Based on the frequencies of their vocalizations, which overlap the frequency range of mid-frequency active sonar, sonar transmissions might temporarily reduce the active space of sperm whale vocalizations. Most of the energy of sperm whales clicks is concentrated at 2 to 4 kHz and 10 to 16 kHz, which overlaps with the mid-frequency sonar. Other studies indicate sperm whales’ wide-band clicks contain energy between 0.1 and 20 kHz (Weilgart and Whitehead 1993, Goold and Jones 1995). Ridgway and Carder (2001) measured low-frequency, high amplitude clicks with peak frequencies at 500 Hz to 3 kHz from a neonate sperm whale. There is some evidence of disruptions of clicking and behavior from sonars (Goold 1999, Watkins and Scheville1975, Watkins et al. 1985), pingers (Watkins and Scheville 1975), the Heard Island Feasability Test (Bowles et al. 1994), and the Acoustic Thermometry of Ocean Climate (Costa et al.1998). Sperm whales have been observed to frequently stop echolocating in the presence of underwater pulses made by echosounders (Watkins and Scheville 1975). Goold (1999) reported six sperm whales that were driven through a narrow channel using ship noise, echosounder, and fishfinder emissions from a flotilla of 10 vessels. Watkins and Scheville (1975) showed that sperm whales interrupted click production in response to pinger (6 to 13 kHz) sounds. They also stopped vocalizing for brief periods when codas were being produced by other individuals, perhaps because they can hear better when not vocalizing themselves (Goold and Jones 1995). 247
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