Taking of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Training Operations Conducted Within the Gulf of Mexico Range Complex, 33960-33986 [E9-16537]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 74, Number 133 (Tuesday, July 14, 2009)]
[Proposed Rules]
[Pages 33960-33986]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-16537]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 218

RIN 0648-AX86


Taking of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to Training Operations Conducted 
Within the Gulf of Mexico Range Complex

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Proposed rule; request for comments.

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SUMMARY: NMFS has received requests from the U.S. Navy (Navy) for 
authorizations for the take of marine mammals incidental to training 
and operational activities conducted by the Navy's Atlantic Fleet 
within the Gulf of Mexico (GOMEX) Range Complex for the period 
beginning December 3, 2009 and ending December 2, 2014. Pursuant to the 
implementing regulations of the Marine Mammal Protection Act (MMPA), 
NMFS is proposing regulations to govern that take and requesting 
information, suggestions, and comments on these proposed regulations.

DATES: Comments and information must be received no later than August 
13, 2009.

ADDRESSES: You may submit comments, identified by 0648-AX86, by any one 
of the following methods:
     Electronic Submissions: Submit all electronic public 
comments via the Federal eRulemaking Portal https://www.regulations.gov.
     Hand delivery or mailing of paper, disk, or CD-ROM 
comments should be addressed to Michael Payne, Chief, Permits, 
Conservation and Education Division, Office of Protected Resources, 
National Marine Fisheries Service, 1315 East-West Highway, Silver 
Spring, MD 20910-3225.
    Instructions: All comments received are part of the public record 
and will generally be posted to https://www.regulations.gov without 
change. All Personal Identifying Information (for example, name, 
address, etc.) voluntarily submitted by the commenter may be publicly 
accessible. Do not submit Confidential Business Information or 
otherwise sensitive or protected information.
    NMFS will accept anonymous comments (enter NA in the required

[[Page 33961]]

fields if you wish to remain anonymous). Attachments to electronic 
comments will be accepted in Microsoft Word, Excel, WordPerfect, or 
Adobe PDF file formats only.

FOR FURTHER INFORMATION CONTACT: Shane Guan, Office of Protected 
Resources, NMFS, (301) 713-2289, ext. 137.

SUPPLEMENTARY INFORMATION:

Availability

    A copy of the Navy's application may be obtained by writing to the 
address specified above (See ADDRESSES), telephoning the contact listed 
above (see FOR FURTHER INFORMATION CONTACT), or visiting the Internet 
at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications. 
The Navy's Draft Environmental Impact Statement (DEIS) for the GOMEX 
Range Complex was published in November 2008, and may be viewed at 
https://www.gomexrangecomplexeis.com/. NMFS participated in the 
development of the Navy's DEIS as a cooperating agency under the 
National Environmental Policy Act (NEPA).

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce (Secretary) to allow, upon request, 
the incidental, but not intentional taking of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) if certain findings are made and regulations are issued or, if 
the taking is limited to harassment, notice of a proposed authorization 
is provided to the public for review.
    Authorization for incidental takings may be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s), will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for subsistence uses, and if 
the permissible methods of taking and requirements pertaining to the 
mitigation, monitoring and reporting of such taking are set forth.
    NMFS has defined ``negligible impact'' in 50 CFR 216.103 as:

    An impact resulting from the specified activity that cannot be 
reasonably expected to, and is not reasonably likely to, adversely 
affect the species or stock through effects on annual rates of 
recruitment or survival.

    With respect to military readiness activities, the MMPA defines 
``harassment'' as:

    (i) Any act that injures or has the significant potential to 
injure a marine mammal or marine mammal stock in the wild [Level A 
Harassment]; or (ii) any act that disturbs or is likely to disturb a 
marine mammal or marine mammal stock in the wild by causing 
disruption of natural behavioral patterns, including, but not 
limited to, migration, surfacing, nursing, breeding, feeding, or 
sheltering, to a point where such behavioral patterns are abandoned 
or significantly altered [Level B Harassment].

Summary of Request

    On October 2, 2008, NMFS received an application from the Navy 
requesting an authorization for the take of marine mammal species/
stocks incidental to the proposed training operations within the GOMEX 
Range Complex over the course of 5 years. These training activities are 
classified as military readiness activities. The Navy states that these 
training activities may cause various impacts to marine mammal species 
in the proposed GOMEX Range Complex Study Area. The Navy requests an 
authorization to take 8 species of cetaceans annually by Level B 
harassment, and 1 individual each of pantropical spotted dolphin and 
spinner dolphin by Level A harassment (injury). Please refer to the 
take table on page 6-17 of the LOA application for detailed information 
of the potential exposures from explosive ordnance (per year) for 
marine mammals in the GOMEX Range Complex. However, due to the 
implementation of the proposed mitigation and monitoring measures, NMFS 
believes that the actual take would be less than estimated.

Description of the Specified Activities

    The GOMEX Study Area encompasses areas at sea, undersea, and 
Special Use Airspace (SUA) in the northern Gulf of Mexico off the coast 
of the U.S. (Figures 1 and 2 of the LOA application). The portions of 
the GOMEX Study Area to be considered for the proposed action consist 
of the BOMBEX Hotbox (surface and subsurface waters) located within the 
Pensacola Operation Area (OPAREA), SUA warning areas W-151A/B/C and W-
155A/B (surface waters), and underwater detonation (UNDET) Area E3 
(surface and subsurface waters), located within the territorial waters 
off Padre Island, Texas, near Corpus Christi NAS. The portions of the 
GOMEX Study Area addressed in the Navy's LOA application encompass:
     1,496 nm\2\ (5,131 km\2\) of sea space (BOMBEX Hotbox, 
where high explosives occur, and UNDET Area E3 where underwater 
detonations occur); and
     11,714 nm\2\ (40,178 km\2\) of SUA warning areas (vessel 
movements only) The BOMBEX Hotbox is an in-water operating and 
maneuvers area with defined air, ocean surface, and subsurface areas. 
The BOMBEX Hotbox is located in the offshore waters of the northeastern 
Gulf of Mexico (GOM) adjacent to Florida and Alabama. The northernmost 
boundary of the BOMBEX Hotbox is located 23 nm (42.6 km) from the coast 
of the Florida panhandle at latitude 30 [deg]N, the eastern boundary is 
approximately 200 nm (370.4 km) from the coast of the Florida peninsula 
at longitude 86[deg]48' W.
    The SUA warning areas, W-151A/B/C and W-155A/B, are in-water 
operating and maneuver areas with defined air and ocean surface. W-
151A/B/C and W-155A/B are located in and above the offshore waters of 
the northeastern GOM adjacent to Florida and Alabama.
    The UNDET Area E3 is a defined surface and subsurface area located 
in the waters south of Corpus Christi NAS and offshore of Padre Island, 
Texas. The westernmost boundary is located 7.5 nm (13.9 km) from the 
coast of Padre Island at 97[deg]9'33'' W and 27[deg]24'26'' N at the 
Western most corner. It lies entirely within the territorial waters (0 
to 12 nm, or 0 to 22.2 km) of the U.S. and the majority of it lies 
within Texas state waters (0 to 9 nm, or 0 to 16.7 km). It is a very 
shallow water training area with depths ranging from 20 to 26 m.
    In the application submitted to NMFS, the Navy requests an 
authorization to take marine mammals incidental to conducting training 
operations within the GOMEX Range Complex. These training activities 
consist of surface warfare. Although vessel movement is also a 
component of the proposed GOMEX Range Complex training activities, the 
Navy concludes that it is unlikely marine mammals would be taken by 
vessel movement with the implementation of mitigation and monitoring 
measures described in the Mitigation Measures and Monitoring Measures 
sections.

Surface Warfare

    Surface Warfare (SUW) supports defense of a geographical area 
(e.g., a zone or barrier) in cooperation with surface, subsurface, and 
air forces. SUW operations detect, localize, and track surface targets, 
primarily ships. Detected ships are monitored visually and with radar. 
Operations include identifying surface contacts, engaging with weapons, 
disengaging, evasion, and avoiding attack, including implementation of 
radio silence and deceptive measures. For the proposed GOMEX Range 
Complex training operations, SUW events involving the use of explosive 
ordnance include air-to-surface Bombing Exercises [BOMEX (A-S)] and 
small arms training (involving explosive hand grenades) that occur at 
sea.

[[Page 33962]]

(A) Bombing Exercise (Air-to-Surface) [BOMEX (A-S)]
    Strike fighter aircraft, such as F/A-18s, deliver explosive bombs 
against at-sea surface targets with the goal of destroying the target. 
BOMBEX (A-S) training in the GOMEX Study Area occurs only during 
daylight hours in the BOMBEX Hotbox area.
    For the proposed BOMBEX (A-S), two aircraft will approach an at-sea 
target from an altitude of between 15,000 ft (4,572 m) to less than 
3,000 ft (914.4 m) and release a high explosive (HE) 1,000-pound (lb) 
bomb on the target. MK-83 bombs would be used. MK-83 bombs have a net 
explosive weight (NEW) of 415.8 lbs. The typical bomb release altitude 
is below 3,000 ft (914.4 m) and the target is usually a flare. The time 
in between bomb drops is approximately 3 minutes.
(B) Small Arms Training (Explosive Hand Grenades)
    Small arms training is a part of quarterly reservist training and 
operational activities for the Mobile Expeditionary Security Group 
(MESG) that operates out of Corpus Christi Naval Air Station (NAS). The 
MESG trains with MK3A2 (0.5-lb NEW) anti-swimmer concussion grenades. 
The MK3A2 grenades are small and contain high explosives in an inert 
metal or plastic shell. They detonate at about 3 m under the water's 
surface within 4 to 5 seconds of being deployed. The detonation depth 
may be shallower depending upon the speed of the boat at the time the 
grenade is deployed.
    A number of different types of boats will be used depending on the 
unit using the boat and their mission. Boats are mostly used by naval 
special warfare (NSW) teams and Navy Expeditionary Combat Command 
(NECC) units (Naval Coastal Warfare, Inshore Boat Units, Mobile 
Security Detachments, Explosive Ordnance Disposal, and Riverine 
Forces). These units are used to protect ships in harbors and high 
value units, such as aircraft carriers, nuclear submarines, liquid 
natural gas tankers, etc., while entering and leaving ports, as well as 
to conduct riverine operations, insertion and extractions, and various 
NSW operations.
    The boats used by these units include: Small Unit River Craft 
(SURC), Combat Rubber Raiding Craft (CRRC), Rigid Hull Inflatable Boats 
(RHIB), Patrol Craft, and many other versions of these types of boats. 
These boats use inboard or outboard, diesel or gasoline engines with 
either propeller or water jet propulsion.
    This exercise is usually a live-fire exercise with M3A2 Anti-
swimmer Concussion Grenades, but at times blanks may be used so boat 
crews can practice their ship-handling skills for the employment of 
weapons without being concerned with the safety requirements involved 
with HE weapons. Boat crews may use high or low speeds to approach and 
engage targets simulating swimmers with anti-swimmer concussion 
grenades. The purpose of this exercise is to develop marksmanship 
skills and small boat ship-handling tactics skills required to employ 
these weapons. Training usually lasts 1-2 hours. Small arms training in 
the GOMEX Study Area will occur during day or evening hours in the 
UNDET Area E3.
    Table 1 summarizes the level of Surface Warfare training activities 
planned in the GOMEX Range Complex for the proposed action.

                            Table 1--Level of Surface Warfare Training Activities Planned in the GOMEX Range Complex per Year
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                      Potential time of
            Operation                   Platform         System/ordnance      Number of events      Training area            day         Event  duration
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bombing Exercise (BOMBEX) (Air-   F/A-18.............  MK-831,000-lb High   1 event (4 bombs in  BOMBEX Hotbox.....  Daytime only......  1 hour.
 to-Surface, At-Sea).                                   Explosive (HE)       succession).
                                                        bomb] 415.8 lbs
                                                        NEW.
Small Arms Training.............  Maritime             MK3A2 anti-swimmer   6 events* (20 live   UNDET Area E3.....  Day or night......  1 hour.
                                   Expeditionary        grenades (8-oz HE    grenades).
                                   Support Group        grenade) 0.5 lb
                                   (Various Small       NEW.
                                   Boats).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* An individual event can include detonation of up to 10 live grenades, but no more than 20 live grenades will be used per year.

Vessel Movement

    Vessel movements are associated with most training and operational 
activities in the GOMEX Study Area. Currently, the number of Navy 
vessels operating in the GOMEX Study Area varies based on training 
schedules and can range from 0 to about 10 vessels at any given time. 
Vessel sizes range from small boats (<35 ft, or 10.7 m) for a harbor 
security boat to 1,092 ft (332.8 m) for a CVN (carrier vessel nuclear) 
and speeds generally range from 10 to 14 knots, but may be considerably 
faster, for example an aircraft carrier ``making wind'' while launching 
and recovering aircraft, and for small boat operations. Operations 
involving vessel movements occur intermittently and are variable in 
duration, ranging from a few hours up to 2 weeks. These operations are 
widely dispersed throughout the GOMEX Study Area, which is an area 
encompassing 11,714 nm\2\ (40,178 km\2\). Most vessel movements occur 
in the offshore OPAREAs, but vessel movements associated with MESG 
training in the UNDET Area E3 and Commander Naval Installations Command 
(CNIC) harbor security group training in the Panama City OPAREA occur 
between shore and 12 nm (22.2 km), including the nearshore zone (<3 nm, 
or 5.6 km). The Navy logs about 180 total vessel days within the GOMEX 
Study Area during a typical year. Consequently, the density of Navy 
vessels within the GOMEX Study Area at any given time is low (i.e., 
less than 0.0113 ships/nm\2\ (0.0386 km\2\)).

Description of Marine Mammals in the Area of the Specified Activities

    Twenty-nine marine mammal species have confirmed or potential 
occurrence in the GOMEX Study Area. These include 28 cetacean species 
and 1 sirenian species (DoN, 2007a), which can be found in Table 2. 
Although it is possible that any of the 29 species of marine mammals 
may occur in the Study Area, only 21 of those species are expected to 
occur regularly in the region. Most cetacean species are in the Study 
Area year-round (e.g., sperm whales and bottlenose dolphins), while a 
few (e.g., fin whales and killer whales) have accidental or transient 
occurrence in the area.

[[Page 33963]]



     Table 2--Marine Mammal Species Found in the GOMEX Range Complex
------------------------------------------------------------------------
   Family and scientific name         Common name       Federal status
------------------------------------------------------------------------
Order Cetacea
------------------------------------------------------------------------
                   Suborder Mysticeti (baleen whales)
------------------------------------------------------------------------
Eubalaena glacialis.............  North Atlantic      Endangered.
                                   right whale.
Megaptera novaeangliae..........  Humpback whale....  Endangered.
Balaenoptera acutorostrata......  Minke whale.......
B. brydei.......................  Bryde's whale.....
B. borealis.....................  Sei whale.........  Endangered.
B. physalus.....................  Fin whale.........  Endangered.
B. musculus.....................  Blue whale........  Endangered.
------------------------------------------------------------------------
                  Suborder Odontoceti (toothed whales)
------------------------------------------------------------------------
Physeter macrocephalus..........  Sperm whale.......  Endangered.
Kogia breviceps.................  Pygmy sperm whale.
K. sima.........................  Dwarf sperm whale.
Ziphius cavirostris.............  Cuvier's beaked
                                   whale.
M. europaeus....................  Gervais' beaked
                                   whale.
M. bidens.......................  Sowerby's beaked
                                   whale.
M. densirostris.................  Blainville's
                                   beaked whale.
Steno bredanensis...............  Rough-toothed
                                   dolphin.
Tursiops truncatus..............  Bottlenose dolphin
Stenella attenuata..............  Pantropical
                                   spotted dolphin.
S. frontalis....................  Atlantic spotted
                                   dolphin.
S. longirostris.................  Spinner dolphin...
S. clymene......................  Clymene dolphin...
S. coeruleoalba.................  Striped dolphin...
Lagenodephis hosei..............  Fraser's dolphin..
Grampus griseus.................  Risso's dolphin...
Peponocephala electra...........  Melon-headed whale
Feresa attenuata................  Pygmy killer whale
Pseudorca crassidens............  False killer whale
Orcinus orca....................  Killer whale......
G. macrorhynchus................  Short-finned pilot
                                   whale.
------------------------------------------------------------------------
                              Order Sirenia
------------------------------------------------------------------------
Trichechus manatus..............  West Indian         Endangered.
                                   manatee.
------------------------------------------------------------------------

    The information contained in this section relies heavily on the 
data gathered in the Marine Resources Assessments (MRAs). The Navy MRA 
Program was implemented by the Commander, Fleet Forces Command, to 
initiate collection of data and information concerning the protected 
and commercial marine resources found in the Navy's OPAREAs. 
Specifically, the goal of the MRA program is to describe and document 
the marine resources present in each of the Navy's OPAREAs. The MRA for 
the GOMEX OPAREA was published in 2007 (DoN, 2007a). The MRA data were 
used to provide a regional context for each species. The MRA represents 
a compilation and synthesis of available scientific literature (e.g., 
journals, periodicals, theses, dissertations, project reports, and 
other technical reports published by government agencies, private 
businesses, or consulting firms), and NMFS reports including stock 
assessment reports (SARs), recovery plans, and survey reports. This 
information was used to evaluate the potential for occurrence of marine 
mammal species in the GOMEX Study Area.
    The density estimates that were used in previous Navy environmental 
documents have been recently updated to provide a compilation of the 
most recent data and information on the occurrence, distribution, and 
density of marine mammals. The updated density estimates presented in 
this LOA application are derived from the Navy OPAREA Density Estimates 
(NODEs) for the GOMEX OPAREA report (DoN, 2007b).
    Density estimates for cetaceans were either modeled using available 
line-transect survey data or derived using cetacean abundance estimates 
found in the 2006 NOAA stock assessment reports (SARs) (Waring et al., 
2007), which can be viewed at https://www.nmfs.noaa.gov/pr/sars/species.htm. The abundance estimates in the stock assessment reports 
are from Mullin and Fulling (2004).
    For the model-based approach, density estimates were calculated for 
each species within areas containing survey effort. A relationship 
between these density estimates and the associated environmental 
parameters such as depth, slope, distance from the shelf break, sea 
surface temperature (SST), and chlorophyll a (chl a) concentration was 
formulated using generalized additive models (GAMs). This relationship 
was then used to generate a two-dimensional density surface for the 
region by predicting densities in areas where no survey data exist.
    The analyses for cetaceans were based on sighting data collected 
through shipboard surveys conducted by NMFS SEFSC between 1996 and 
2004. Species-specific density estimates derived through spatial 
modeling were compared with abundance estimates found in the 2006 NOAA 
SARs to ensure consistency. All spatial models and density estimates 
were reviewed by and coordinated with NMFS Science

[[Page 33964]]

Center technical staff and scientists with the University of St. 
Andrews, Scotland, Centre for Environmental and Ecological Modeling 
(CREEM). For a more detailed description of the methods involved in 
calculating the density estimates provided in this LOA request, please 
refer to the NODE report for the GOMEX OPAREA (DoN, 2007b). The 
following lists how density estimates were derived for each species:

Model-Derived Density Estimates--Line Transect Survey Data

    Sperm whale, dwarf and pygmy sperm whales, beaked whales, rough-
toothed dolphin, bottlenose dolphin (Tursiops truncatus), pantropical 
spotted dolphin, Atlantic spotted dolphin, striped dolphin, spinner 
dolphin, and Risso's dolphin.

Stock Assessment Report or Literature-Derived Density Estimates

    Bryde's whale, Clymene dolphin, Fraser's dolphin, killer whale, 
false killer whale, pygmy killer whale, melon-headed whale, short-
finned pilot whale.

Potential Impacts to Marine Mammal Species

    The Navy considers that explosions associated with BOMBEX (A-S) and 
small arms training are the activities with the potential to result in 
Level A or Level B harassment of marine mammals. Vessel strikes were 
also analyzed for potential effect to marine mammals.

Vessel Strikes

    Collisions with commercial and Navy ships can result in serious 
injury and may occasionally cause fatalities to cetaceans and manatees. 
Although the most vulnerable marine mammals may be assumed to be slow-
moving cetaceans or those that spend extended periods of time at the 
surface in order to restore oxygen levels within their tissues after 
deep dives (e.g., sperm whale), fin whales are actually struck most 
frequently (Laist et al., 2001). Manatees are also particularly 
susceptible to vessel interactions and collisions with watercraft 
constitute the leading cause of mortality (USFWS, 2007). Smaller marine 
mammals such as bottlenose and Atlantic spotted dolphins move more 
quickly throughout the water column and are often seen riding the bow 
wave of large ships. Marine mammal responses to vessels may include 
avoidance and changes in dive patterns (NRC, 2003).
    After reviewing historical records and computerized stranding 
databases for evidence of ship strikes involving baleen and sperm 
whales, Laist et al. (2001) found that accounts of large whale ship 
strikes involving motorized boats in the area date back to at least the 
late 1800s. Ship collisions remained infrequent until the 1950s, after 
which point they increased. Laist et al. (2001) report that both the 
number and speed of motorized vessels have increased over time for 
trans-Atlantic passenger services, which transit through the area. They 
concluded that most strikes occur over or near the continental shelf, 
that ship strikes likely have a negligible effect on the status of most 
whale populations, but that for small populations or segments of 
populations the impact of ship strikes may be significant.
    Although ship strikes may result in the mortality of a limited 
number of whales within a population or stock, Laist et al. (2001) also 
concluded that, when considered in combination with other human-related 
mortalities in the area (e.g., entanglement in fishing gear), these 
ship strikes may present a concern for whale populations.
    Of 11 species known to be hit by ships, fin whales are struck most 
frequently; followed by right whales, humpback whales, sperm whales, 
and gray whales (Laist et al., 2001). In some areas, one-third of all 
fin whale and right whale strandings appear to involve ship strikes. 
Sperm whales spend long periods (typically up to 10 minutes; Jacquet et 
al., 1996) ``rafting'' at the surface between deep dives. This could 
make them exceptionally vulnerable to ship strikes. Berzin (1972) noted 
that there were ``many'' reports of sperm whales of different age 
classes being struck by vessels, including passenger ships and tug 
boats. There were also instances in which sperm whales approached 
vessels too closely and were cut by the propellers (NMFS, 2006).
    In the Gulf of Mexico, sperm whales are of particular concern. 
Sperm whales spend extended periods of time at the surface in order to 
restore oxygen levels within their tissues after deep dives. In 
addition, some baleen whales such as the North Atlantic right whale 
seem generally unresponsive to vessel sound, making them more 
susceptible to vessel collisions (Nowacek et al., 2004a). In comparison 
with other regions of the U.S., the Gulf of Mexico is the least common 
area for ship strikes of large whales (Jensen and Silber, 2003). 
Between 1972 and 1999, eight confirmed or possible large whale ship 
strikes were recorded in the Gulf of Mexico, including two that 
collided with Navy vessels; four of these resulted in mortality of the 
animal (Jensen and Silber, 2003) and one resulted in extensive damage 
to a Navy vessel (Laist et al., 2001). It is not known whether the 
shipstrikes involving Navy vessels resulted in the mortality of the 
animal (Laist et al., 2001; Jensen and Silber, 2003).
    Accordingly, the Navy has proposed mitigation measures to reduce 
the potential for collisions with surfaced marine mammals (for more 
details refer to Proposed Mitigation Measures below). Based on the 
implementation of Navy mitigation measures and the relatively low 
density of Navy ships in the Study Area the likelihood that a vessel 
collision would occur is very low.

Vessel Movement

    There are limited data concerning marine mammal behavioral 
responses to vessel traffic and vessel noise, and a lack of consensus 
among scientists with respect to what these responses mean or whether 
they result in short-term or long-term adverse effects. In those cases 
where there is a busy shipping lane or where there is large amount of 
vessel traffic, marine mammals may experience acoustic masking 
(Hildebrand, 2005) if they are present in the area (e.g., killer whales 
in Puget Sound; Foote et al., 2004; Holt et al., 2008). In cases where 
vessels actively approach marine mammals (e.g., whale watching or 
dolphin watching boats), scientists have documented that animals 
exhibit altered behavior such as increased swimming speed, erratic 
movement, and active avoidance behavior (Bursk, 1983; Acevedo, 1991; 
Baker and MacGibbon, 1991; Trites and Bain, 2000; Williams et al., 
2002; Constantine et al., 2003), reduced blow interval (Ritcher et al., 
2003), disruption of normal social behaviors (Lusseau, 2003; 2006), and 
the shift of behavioral activities which may increase energetic costs 
(Constantine et al., 2003; 2004)). A detailed review of marine mammal 
reactions to ships and boats is available in Richardson et al. (1995). 
For each of the marine mammals taxonomy groups, Richardson et al. 
(1995) provided the following assessment regarding cetacean reactions 
to vessel traffic:
    Toothed whales: ``In summary, toothed whales sometimes show no 
avoidance reaction to vessels, or even approach them. However, 
avoidance can occur, especially in response to vessels of types used to 
chase or hunt the animals. This may cause temporary displacement, but 
we know of no clear evidence that toothed whales have abandoned 
significant parts of their range because of vessel traffic.''
    Baleen whales: ``When baleen whales receive low-level sounds from 
distant or

[[Page 33965]]

stationary vessels, the sounds often seem to be ignored. Some whales 
approach the sources of these sounds. When vessels approach whales 
slowly and nonaggressively, whales often exhibit slow and inconspicuous 
avoidance maneuvers. In response to strong or rapidly changing vessel 
noise, baleen whales often interrupt their normal behavior and swim 
rapidly away. Avoidance is especially strong when a boat heads directly 
toward the whale.''
    It is important to recognize that behavioral responses to stimuli 
are complex and influenced to varying degrees by a number of factors 
such as species, behavioral contexts, geographical regions, source 
characteristics (moving or stationary, speed, direction, etc.), prior 
experience of the animal, and physical status of the animal. For 
example, studies have shown that beluga whales reacted differently when 
exposed to vessel noise and traffic. In some cases, naive beluga whales 
exhibited rapid swimming from ice-breaking vessels up to 80 km away, 
and showed changes in surfacing, breathing, diving, and group 
composition in the Canadian high Arctic where vessel traffic is rare 
(Finley et al., 1990). In other cases, beluga whales were more tolerant 
of vessels, but differentially responsive by reducing their calling 
rates, to certain vessels and operating characteristics (especially 
older animals) in the St. Lawrence River where vessel traffic is common 
(Blane and Jaakson, 1994). In Bristol Bay, Alaska, beluga whales 
continued to feed when surrounded by fishing vessels and resisted 
dispersal even when purposefully harassed (Fish and Vania, 1971).
    In reviewing more than 25 years of whale observation data, Watkins 
(1986) concluded that whale reactions to vessel traffic were ``modified 
by their previous experience and current activity: habituation often 
occurred rapidly, attention to other stimuli or preoccupation with 
other activities sometimes overcame their interest or wariness of 
stimuli.'' Watkins noticed that over the years of exposure to ships in 
the Cape Cod area, minke whales (Balaenoptera acutorostrata) changed 
from frequent positive (such as approaching vessels) interest to 
generally uninterested reactions; finback whales (B. physalus) changed 
from mostly negative (such as avoidance) to uninterested reactions; 
right whales (Eubalaena glacialis) apparently continued the same 
variety of responses (negative, uninterested, and positive responses) 
with little change; and humpbacks (Megaptera novaeangliae) dramatically 
changed from mixed responses that were often negative to often strongly 
positive reactions. Watkins (1986) summarized that ``whales near shore, 
even in regions with low vessel traffic, generally have become less 
wary of boats and their noises, and they have appeared to be less 
easily disturbed than previously. In particular locations with intense 
shipping and repeated approaches by boats (such as the whale-watching 
areas of Stellwagen Bank), more and more whales had P [positive] 
reactions to familiar vessels, and they also occasionally approached 
other boats and yachts in the same ways.''
    In the case of the GOMEX Range Complex, naval vessel traffic is 
expected to be much lower than in areas where there are large shipping 
lanes and large numbers of fishing vessels and/or recreational vessels. 
Nevertheless, the proposed action area is well traveled by a variety of 
commercial and recreational vessels, so marine mammals in the area are 
expected to be habituated to vessel noise.
    As described earlier in this document, operations involving vessel 
movements occur intermittently and are variable in duration, ranging 
from a few hours up to 2 weeks. These operations are widely dispersed 
throughout the GOMEX Range Complex OPAREA, which is a vast area 
encompassing 11,714 nm\2\. The Navy logs about 180 total vessel days 
within the Study Area during a typical year. Consequently, the density 
of ships within the Study Area at any given time is extremely low 
(i.e., less than 0.0113 ships/nm\2\).
    Moreover, naval vessels transiting the study area or engaging in 
the training exercises will not actively or intentionally approach a 
marine mammal or change speed drastically. All vessels transiting to, 
from, and within the range complexes will be traveling at speeds 
generally ranging from 10 to 14 knots. In addition, mitigation measures 
described below require Navy vessels to keep at least 500 yards (460 m) 
away from any observed whale and at least 200 yards (183 m) from marine 
mammals other than whales, and avoid approaching animals head-on. 
Although the radiated sound from the vessels will be audible to marine 
mammals over a large distance, it is unlikely that animals will respond 
behaviorally to low-level distant shipping noise as the animals in the 
area are likely to be habituated to such noises (Nowacek et al., 2004). 
In light of these facts, NMFS does not expect the Navy's vessel 
movements to result in Level B harassment.

Assessment of Marine Mammal Response to Anthropogenic Sound

    Marine mammals respond to various types of anthropogenic sounds 
introduced in the ocean environment. Responses are typically subtle and 
can include shorter surfacings, shorter dives, fewer blows per 
surfacing, longer intervals between blows (breaths), ceasing or 
increasing vocalizations, shortening or lengthening vocalizations, and 
changing frequency or intensity of vocalizations (NRC, 2005). However, 
it is not known how these responses relate to significant effects 
(e.g., long-term effects or population consequences). The following is 
an assessment of marine mammal responses and disturbances when exposed 
to anthropogenic sound.

I. Physiology

    Potential impacts to the auditory system are assessed by 
considering the characteristics of the received sound (e.g., amplitude, 
frequency, duration) and the sensitivity of the exposed animals. Some 
of these assessments can be numerically based (e.g., temporary 
threshold shift [TTS] of hearing sensitivity, permanent threshold shift 
[PTS] of hearing sensitivity, perception). Others will be necessarily 
qualitative, due to a lack of information, or will need to be 
extrapolated from other species for which information exists.
    Potential physiological responses to the sound exposure are ranked 
in descending order, with the most severe impact (auditory trauma) 
occurring at the top and the least severe impact occurring at the 
bottom (the sound is not perceived).
    Auditory trauma represents direct mechanical injury to hearing 
related structures, including tympanic membrane rupture, 
disarticulation of the middle ear ossicles, and trauma to the inner ear 
structures such as the organ of Corti and the associated hair cells. 
Auditory trauma is always injurious that could result in PTS and is 
always assumed to result in a stress response.
    Auditory fatigue refers to a loss of hearing sensitivity after 
sound stimulation. The loss of sensitivity persists after, sometimes 
long after, the cessation of the sound. The mechanisms responsible for 
auditory fatigue differ from auditory trauma and would primarily 
consist of metabolic exhaustion of the hair cells and cochlear tissues. 
The features of the exposure (e.g., amplitude, frequency, duration, 
temporal pattern) and the individual animal's susceptibility would 
determine the severity of fatigue and whether the

[[Page 33966]]

effects were temporary (TTS) or permanent (PTS). Auditory fatigue (PTS 
or TTS) is always assumed to result in a stress response.
    Sounds with sufficient amplitude and duration to be detected among 
the background ambient noise are considered to be perceived. This 
category includes sounds from the threshold of audibility through the 
normal dynamic range of hearing (i.e., not capable of producing 
fatigue).
    To determine whether an animal perceives the sound, the received 
level, frequency, and duration of the sound are compared to what is 
known of the species' hearing sensitivity.
    Since audible sounds may interfere with an animal's ability to 
detect other sounds at the same time, perceived sounds have the 
potential to result in auditory masking. Unlike auditory fatigue, which 
always results in a stress response because the sensory tissues are 
being stimulated beyond their normal physiological range, masking may 
or may not result in a stress response, depending on the degree and 
duration of the masking effect. Masking may also result in a unique 
circumstance where an animal's ability to detect other sounds is 
compromised without the animal's knowledge. This could conceivably 
result in sensory impairment and subsequent behavior change; in this 
case, the change in behavior is the lack of a response that would 
normally be made if sensory impairment did not occur. For this reason, 
masking also may lead directly to behavior change without first causing 
a stress response.
    The features of perceived sound (e.g., amplitude, duration, 
temporal pattern) are also used to judge whether the sound exposure is 
capable of producing a stress response. Factors to consider in this 
decision include the probability of the animal being naive or 
experienced with the sound (i.e., what are the known/unknown 
consequences of the exposure).
    If the received level is not of sufficient amplitude, frequency, 
and duration to be perceptible by the animal, by extension, this does 
not result in a stress response (not perceived). Potential impacts to 
tissues other than those related to the auditory system are assessed by 
considering the characteristics of the sound (e.g., amplitude, 
frequency, duration) and the known or estimated response 
characteristics of non-auditory tissues. Some of these assessments can 
be numerically based (e.g., exposure required for rectified diffusion). 
Others will be necessarily qualitative, due to lack of information. 
Each of the potential responses may or may not result in a stress 
response.
    Direct tissue effects--Direct tissue responses to sound stimulation 
may range from tissue shearing (injury) to mechanical vibration with no 
resulting injury.
    No tissue effects--The received sound is insufficient to cause 
either direct (mechanical) or indirect effects to tissues. No stress 
response occurs.

II. The Stress Response

    The acoustic source is considered a potential stressor if, by its 
action on the animal, via auditory or non-auditory means, it may 
produce a stress response in the animal. The term ``stress'' has taken 
on an ambiguous meaning in the scientific literature, but with respect 
to the later discussions of allostasis and allostatic loading, the 
stress response will refer to an increase in energetic expenditure that 
results from exposure to the stressor and which is predominantly 
characterized by either the stimulation of the sympathetic nervous 
system (SNS) or the hypothalamic-pituitary-adrenal (HPA) axis (Reeder 
and Kramer, 2005). The SNS response to a stressor is immediate and 
acute and is characterized by the release of the catecholamine 
neurohormones norepinephrine and epinephrine (i.e., adrenaline). These 
hormones produce elevations in the heart and respiration rate, increase 
awareness, and increase the availability of glucose and lipids for 
energy. The HPA response is ultimately defined by increases in the 
secretion of the glucocorticoid steroid hormones, predominantly 
cortisol in mammals. The amount of increase in circulating 
glucocorticoids above baseline may be an indicator of the overall 
severity of a stress response (Hennessy et al., 1979). Each component 
of the stress response is variable in time; e.g., adrenalines are 
released nearly immediately and are used or cleared by the system 
quickly, whereas cortisol levels may take long periods of time to 
return to baseline.
    The presence and magnitude of a stress response in an animal 
depends on a number of factors. These include the animal's life history 
stage (e.g., neonate, juvenile, adult), the environmental conditions, 
reproductive or developmental state, and experience with the stressor. 
Not only will these factors be subject to individual variation, but 
they will also vary within an individual over time. In considering 
potential stress responses of marine mammals to acoustic stressors, 
each of these should be considered. For example, is the acoustic 
stressor in an area where animals engage in breeding activity? Are 
animals in the region resident and likely to have experience with the 
stressor (i.e., repeated exposures)? Is the region a foraging ground or 
are the animals passing through as transients? What is the ratio of 
young (naive) to old (experienced) animals in the population? It is 
unlikely that all such questions can be answered from empirical data; 
however, they should be addressed in any qualitative assessment of a 
potential stress response as based on the available literature.
    The stress response may or may not result in a behavioral change, 
depending on the characteristics of the exposed animal. However, 
provided a stress response occurs, we assume that some contribution is 
made to the animal's allostatic load. Allostasis is the ability of an 
animal to maintain stability through change by adjusting its physiology 
in response to both predictable and unpredictable events (McEwen and 
Wingfield, 2003). The same hormones associated with the stress response 
vary naturally throughout an animal's life, providing support for 
particular life history events (e.g., pregnancy) and predictable 
environmental conditions (e.g., seasonal changes). The allostatic load 
is the cumulative cost of allostasis incurred by an animal and is 
generally characterized with respect to an animal's energetic 
expenditure. Perturbations to an animal that may occur with the 
presence of a stressor, either biological (e.g., predator) or 
anthropogenic (e.g., construction), can contribute to the allostatic 
load (Wingfield, 2003). Additional costs are cumulative and additions 
to the allostatic load over time may contribute to reductions in the 
probability of achieving ultimate life history functions (e.g., 
survival, maturation, reproductive effort and success) by producing 
pathophysiological states (the conditions of disease or injury). The 
contribution to the allostatic load from a stressor requires estimating 
the magnitude and duration of the stress response, as well as any 
secondary contributions that might result from a change in behavior.
    If the acoustic source does not produce tissue effects, is not 
perceived by the animal, or does not produce a stress response by any 
other means, we assume that the exposure does not contribute to the 
allostatic load. Additionally, without a stress response or auditory 
masking, it is assumed that there can be no behavioral change. 
Conversely, any immediate effect of exposure that produces an injury is 
assumed to also produce a stress response and contribute to the 
allostatic load.

[[Page 33967]]

III. Behavior

    Changes in marine mammal behavior are expected to result from an 
acute stress response. This expectation is based on the idea that some 
sort of physiological trigger must exist to change any behavior that is 
already being performed. The exception to this rule is the case of 
auditory masking. The presence of a masking sound may not produce a 
stress response, but may interfere with the animal's ability to detect 
and discriminate biologically relevant signals. The inability to detect 
and discriminate biologically relevant signals hinders the potential 
for normal behavioral responses to auditory cues and is thus considered 
a behavioral change.
    Impulsive sounds from explosions have very short durations as 
compared to other sounds like sonar or ship noise, which are more 
likely to produce auditory masking. Additionally the explosive sources 
analyzed in this document are used infrequently and the training events 
are typically of short duration. Therefore, the potential for auditory 
masking is unlikely.
    Numerous behavioral changes can occur as a result of stress 
response. For each potential behavioral change, the magnitude in the 
change and the severity of the response needs to be estimated. Certain 
conditions, such as stampeding (i.e., flight response) or a response to 
a predator, might have a probability of resulting in injury. For 
example, a flight response, if significant enough, could produce a 
stranding event. Each disruption to a natural behavioral pattern (e.g., 
breeding or nursing) may need to be classified as Level B harassment. 
All behavioral disruptions have the potential to contribute to the 
allostatic load. This secondary potential is signified by the feedback 
from the collective behaviors to allostatic loading.

IV. Life Function

IV.1. Proximate Life Functions
    Proximate life history functions are the functions that the animal 
is engaged in at the time of acoustic exposure. The disruption of these 
functions, and the magnitude of the disruption, is something that must 
be considered in determining how the ultimate life history functions 
are affected. Consideration of the magnitude of the effect to each of 
the proximate life history functions is dependent upon the life stage 
of the animal. For example, an animal on a breeding ground which is 
sexually immature will suffer relatively little consequence to 
disruption of breeding behavior when compared to an actively displaying 
adult of prime reproductive age.
IV.2. Ultimate Life Functions
    The ultimate life functions are those that enable an animal to 
contribute to the population (or stock, or species, etc.). The impact 
to ultimate life functions will depend on the nature and magnitude of 
the perturbation to proximate life history functions. Depending on the 
severity of the response to the stressor, acute perturbations may have 
nominal to profound impacts on ultimate life functions. For example, 
unit-level use of sonar by a vessel transiting through an area that is 
utilized for foraging, but not for breeding, may disrupt feeding by 
exposed animals for a brief period of time. Because of the brevity of 
the perturbation, the impact to ultimate life functions may be 
negligible. By contrast, weekly training over a period of years may 
have a more substantial impact because the stressor is chronic. 
Assessment of the magnitude of the stress response from the chronic 
perturbation would require an understanding of how and whether animals 
acclimate to a specific, repeated stressor and whether chronic 
elevations in the stress response (e.g., cortisol levels) produce 
fitness deficits.
    The proximate life functions are loosely ordered in decreasing 
severity of impact. Mortality (survival) has an immediate effect, in 
that no future reproductive success is feasible and there is no further 
addition to the population resulting from reproduction. Severe injuries 
may also lead to reduced survivorship (longevity) and prolonged 
alterations in behavior. The latter may further affect an animal's 
overall reproductive success and reproductive effort. Disruptions of 
breeding have an immediate impact on reproductive effort and may impact 
reproductive success. The magnitude of the effect will depend on the 
duration of the disruption and the type of behavior change that was 
provoked. Disruptions to feeding and migration can affect all of the 
ultimate life functions; however, the impacts to reproductive effort 
and success are not likely to be as severe or immediate as those 
incurred by mortality and breeding disruptions.

Explosive Ordnance Exposure Analysis

    The underwater explosion from a weapon would send a shock wave and 
blast noise through the water, release gaseous by-products, create an 
oscillating bubble, and cause a plume of water to shoot up from the 
water surface. The shock wave and blast noise are of most concern to 
marine animals. The effects of an underwater explosion on a marine 
mammal depends on many factors, including the size, type, and depth of 
both the animal and the explosive charge; the depth of the water 
column; and the standoff distance between the charge and the animal, as 
well as the sound propagation properties of the environment. Potential 
impacts can range from brief effects (such as behavioral disturbance), 
tactile perception, physical discomfort, slight injury of the internal 
organs and the auditory system, to death of the animal (Yelverton et 
al., 1973; O'Keeffe and Young, 1984; DoN, 2001). Non-lethal injury 
includes slight injury to internal organs and the auditory system; 
however, delayed lethality can be a result of individual or cumulative 
sublethal injuries (DoN, 2001). Immediate lethal injury would be a 
result of massive combined trauma to internal organs as a direct result 
of proximity to the point of detonation (DoN, 2001). Generally, the 
higher the level of impulse and pressure level exposure, the more 
severe the impact to an individual.
    Injuries resulting from a shock wave take place at boundaries 
between tissues of different density. Different velocities are imparted 
to tissues of different densities, and this can lead to their physical 
disruption. Blast effects are greatest at the gas-liquid interface 
(Landsberg, 2000). Gas-containing organs, particularly the lungs and 
gastrointestinal tract, are especially susceptible (Goertner, 1982; 
Hill, 1978; Yelverton et al., 1973). In addition, gas-containing organs 
including the nasal sacs, larynx, pharynx, trachea, and lungs may be 
damaged by compression/expansion caused by the oscillations of the 
blast gas bubble (Reidenberg and Laitman, 2003). Intestinal walls can 
bruise or rupture, with subsequent hemorrhage and escape of gut 
contents into the body cavity. Less severe gastrointestinal tract 
injuries include contusions, petechiae (small red or purple spots 
caused by bleeding in the skin), and slight hemorrhaging (Yelverton et 
al., 1973).
    Because the ears are the most sensitive to pressure, they are the 
organs most sensitive to injury (Ketten, 2000). Sound-related damage 
associated with blast noise can be theoretically distinct from injury 
from the shock wave, particularly farther from the explosion. If an 
animal is able to hear a noise, at some level it can damage its hearing 
by causing decreased sensitivity (Ketten, 1995) (See Assessment of 
Marine Mammal Response to Anthropogenic Sound Section above). Sound-
related trauma can be lethal or sublethal. Lethal

[[Page 33968]]

impacts are those that result in immediate death or serious 
debilitation in or near an intense source and are not, technically, 
pure acoustic trauma (Ketten, 1995). Sublethal impacts include hearing 
loss, which is caused by exposures to perceptible sounds. Severe damage 
(from the shock wave) to the ears includes tympanic membrane rupture, 
fracture of the ossicles, damage to the cochlea, hemorrhage, and 
cerebrospinal fluid leakage into the middle ear. Moderate injury 
implies partial hearing loss due to tympanic membrane rupture and blood 
in the middle ear. Permanent hearing loss also can occur when the hair 
cells are damaged by one very loud event, as well as by prolonged 
exposure to a loud noise or chronic exposure to noise. The level of 
impact from blasts depends on both an animal's location and, at outer 
zones, on its sensitivity to the residual noise (Ketten, 1995).
    The exercises that use explosives in this request include BOMBEX 
(A-S) and GUNEX (S-S). Table 1 summarizes the number of events and 
specific areas where each occurs for each type of explosive ordnance 
used. There is no difference in how many events take place between the 
different seasons. Fractional values are a result of evenly 
distributing the annual totals over the four seasons. For example, 
there is one BOXEX event per year that can take place in the BOMBEX 
Hotbox during any season, so there are 0.25 event modeled for each 
season.

Definition of Harassment

    As mentioned previously, with respect to military readiness 
activities, Section 3(18)(B) of the MMPA defines ``harassment'' as: (i) 
Any act that injures or has the significant potential to injure a 
marine mammal or marine mammal stock in the wild [Level A Harassment]; 
or (ii) any act that disturbs or is likely to disturb a marine mammal 
or marine mammal stock in the wild by causing disruption of natural 
behavioral patterns, including, but not limited to, migration, 
surfacing, nursing, breeding, feeding, or sheltering, to a point where 
such behavioral patterns are abandoned or significantly altered [Level 
B Harassment].

I. Level B Harassment

    Of the potential effects that were described in the Assessment of 
Marine Mammal Response to Anthropogenic Sound and the Explosive 
Ordnance Exposure Analysis sections, the following are the types of 
effects that fall into the Level B Harassment category:
    (A) Behavioral Harassment--Behavioral disturbance that rises to the 
level described in the definition above, when resulting from exposures 
to underwater detonations, is considered Level B Harassment. Some of 
the lower level physiological stress responses discussed in the 
Assessment of Marine Mammal Response to Anthropogenic Sound section 
will also likely co-occur with the predicted harassments, although 
these responses are more difficult to detect and fewer data exist 
relating these responses to specific received levels of sound. When 
Level B Harassment is predicted based on estimated behavioral 
responses, those takes may have a stress-related physiological 
component as well.
    (B) Acoustic Masking and Communication Impairment--Acoustic masking 
is considered Level B Harassment as it can disrupt natural behavioral 
patterns by interrupting or limiting the marine mammal's receipt or 
transmittal of important information or environmental cues.
    (C) TTS--As discussed previously, TTS can affect how an animal 
behaves in response to the environment, including conspecifics, 
predators, and prey. The following physiological mechanisms are thought 
to play a role in inducing auditory fatigue: effects to sensory hair 
cells in the inner ear that reduce their sensitivity, modification of 
the chemical environment within the sensory cells, residual muscular 
activity in the middle ear, displacement of certain inner ear 
membranes, increased blood flow, and post-stimulatory reduction in both 
efferent and sensory neural output. Ward (1997) suggested that when 
these effects result in TTS rather than PTS, they are within the normal 
bounds of physiological variability and tolerance and do not represent 
a physical injury. Additionally, Southall et al. (2007) indicate that 
although PTS is a tissue injury, TTS is not because the reduced hearing 
sensitivity following exposure to intense sound results primarily from 
fatigue, not loss, of cochlear hair cells and supporting structures and 
is reversible. Accordingly, NMFS classifies TTS (when resulting from 
exposure to underwater detonations) as Level B Harassment, not Level A 
Harassment (injury).

II. Level A Harassment

    Of the potential effects that were described in the Assessment of 
Marine Mammal Response to Anthropogenic Sound section, the following 
are the types of effects that fall into the Level A Harassment 
category:
    (A) PTS--PTS is irreversible and considered to be an injury. PTS 
results from exposure to intense sounds that cause a permanent loss of 
inner or outer cochlear hair cells or exceed the elastic limits of 
certain tissues and membranes in the middle and inner ears and result 
in changes in the chemical composition of the inner ear fluids.
    (B) Physical Disruption of Tissues Resulting from Explosive Shock 
Wave--Physical damage of tissues resulting from a shock wave (from an 
explosive detonation) is classified as an injury. Blast effects are 
greatest at the gas-liquid interface (Landsberg, 2000) and gas-
containing organs, particularly the lungs and gastrointestinal tract, 
are especially susceptible to damage (Goertner, 1982; Hill 1978; 
Yelverton et al., 1973). Nasal sacs, larynx, pharynx, trachea, and 
lungs may be damaged by compression/expansion caused by the 
oscillations of the blast gas bubble (Reidenberg and Laitman, 2003). 
Severe damage (from the shock wave) to the ears can include tympanic 
membrane rupture, fracture of the ossicles, damage to the cochlea, 
hemorrhage, and cerebrospinal fluid leakage into the middle ear.

Acoustic Take Criteria

    For the purposes of an MMPA incidental take authorization, three 
types of take are identified: Level B Harassment; Level A Harassment; 
and mortality (or serious injury leading to mortality). The categories 
of marine mammal responses (physiological and behavioral) that fall 
into the two harassment categories were described in the previous 
section.
    Because the physiological and behavioral responses of the majority 
of the marine mammals exposed to underwater detonations cannot be 
detected or measured, a method is needed to estimate the number of 
individuals that will be taken, pursuant to the MMPA, based on the 
proposed action. To this end, NMFS uses an acoustic criteria that 
estimate at what received level (when exposed to explosive detonations) 
Level B Harassment, Level A Harassment, and mortality (for explosives) 
of marine mammals would occur. The acoustic criteria for Underwater 
Detonations are discussed.

Thresholds and Criteria for Impulsive Sound

    Criteria and thresholds for estimating the exposures from a single 
explosive activity on marine mammals were established for the Seawolf 
Submarine Shock Test Final Environmental Impact Statement (FEIS) 
(``Seawolf'') and subsequently used in the USS Winston

[[Page 33969]]

S. Churchill (DDG-81) Ship Shock FEIS (``Churchill'') (DoN, 1998 and 
2001a). NMFS adopted these criteria and thresholds in its final rule on 
unintentional taking of marine animals occurring incidental to the 
shock testing (NMFS, 2001a). Since the ship-shock events involve only 
one large explosive at a time, additional assumptions were made to 
extend the approach to cover multiple explosions for BOMBEX (A-S). In 
addition, this section reflects a revised acoustic criterion for small 
underwater explosions (i.e., 23 pounds per square inch [psi] instead of 
previous acoustic criteria of 12 psi for peak pressure), which is based 
on the final rule issued to the Air Force by NMFS (NMFS, 2005b).
I.1. Thresholds and Criteria for Injurious Physiological Impacts
I.1.a. Single Explosion
    For injury, NMFS uses dual criteria: eardrum rupture (i.e., 
tympanic-membrane injury) and onset of slight lung injury. These 
criteria are considered indicative of the onset of injury. The 
threshold for tympanic-membrane (TM) rupture corresponds to a 50 
percent rate of rupture (i.e., 50 percent of animals exposed to the 
level are expected to suffer TM rupture). This value is stated in terms 
of an Energy Flux Density Level (EL) value of 1.17 inch pounds per 
square inch (in-lb/in \2\), approximately 205 dB re 1 microPa \2\-sec.
    The threshold for onset of slight lung injury is calculated for a 
small animal (a dolphin calf weighing 26.9 lbs), and is given in terms 
of the ``Goertner modified positive impulse,'' indexed to 13 psi-msec 
(DoN, 2001). This threshold is conservative since the positive impulse 
needed to cause injury is proportional to animal mass, and therefore, 
larger animals require a higher impulse to cause the onset of injury. 
This analysis assumed the marine species populations were 100 percent 
small animals. The criterion with the largest potential impact range 
(most conservative), either TM rupture (energy threshold) or onset of 
slight lung injury (peak pressure), will be used in the analysis to 
determine Level A exposures for single explosive events.
    For mortality, NMFS uses the criterion corresponding to the onset 
of extensive lung injury. This is conservative in that it corresponds 
to a 1 percent chance of mortal injury, and yet any animal experiencing 
onset severe lung injury is counted as a lethal exposure. For small 
animals, the threshold is given in terms of the Goertner modified 
positive impulse, indexed to 30.5 psi-msec. Since the Goertner approach 
depends on propagation, source/animal depths, and animal mass in a 
complex way, the actual impulse value corresponding to the 30.5 psi-
msec index is a complicated calculation. To be conservative, the 
analysis used the mass of a calf dolphin (at 26.9 lbs) for 100 percent 
of the populations.
I.1.b. Multiple Explosions
    For this analysis, the use of multiple explosions only applies to 
the MK-83 bombs used in BOMBEX. Since BOMBEX events require multiple 
explosions, the Churchill approach had to be extended to cover multiple 
sound events at the same training site. For multiple exposures, 
accumulated energy over the entire training time is the natural 
extension for energy thresholds since energy accumulates with each 
subsequent shot (explosion); this is consistent with the treatment of 
multiple arrivals in Churchill. For positive impulse, it is consistent 
with Churchill to use the maximum value over all impulses received.
I.2. Thresholds and Criteria for Non-Injurious Physiological Effects
    The NMFS' criterion for non-injurious harassment is TTS--a slight, 
recoverable loss of hearing sensitivity (DoN, 2001). For this 
assessment, there are dual criteria for TTS, an energy threshold and a 
peak pressure threshold. The criterion with the largest potential 
impact range (most conservative) either the energy or peak pressure 
threshold, will be used in the analysis to determine Level B TTS 
exposures.
I.2.a. Single Explosion--TTS-Energy Threshold
    The first threshold is a 182 dB re 1 microPa \2\-sec maximum energy 
flux density level in any \1/3\-octave band at frequencies above 100 
Hertz (Hz) for toothed whales and in any \1/3\-octave band above 10 Hz 
for baleen whales. For large explosives, as in the case of the 
Churchill FEIS, frequency range cutoffs at 10 and 100 Hz make a 
difference in the range estimates. For small explosives (<1,500 lb 
NEW), as what was modeled for this analysis, the spectrum of the shot 
arrival is broad, and there is essentially no difference in impact 
ranges for toothed whales or baleen whales.
    The TTS energy threshold for explosives is derived from the Space 
and Naval Warfare Systems Center (SSC) pure-tone tests for TTS 
(Schlundt et al., 2000; Finneran and Schlundt, 2004). The pure-tone 
threshold (192 dB as the lowest value) is modified for explosives by 
(a) interpreting it as an energy metric,