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OCR for page 21
2 Evaluation of the Marine r
Mammal Research Program
DESCRIPTION OF MMRP RESULTS
The sound source used by the Acoustic Thermometry of Ocean Climate
(ATOC) experiment is acoustically different from the source used in the previous
Heard Island Feasibility Test (HIFT), in part due to concerns about potential
effects on marine mammals and in part to the shorter distance between the ATOC
sources and receivers. In fact, information obtained from HIFT indicated that a
less intense sound source (HIFT used a level of 221 dB) could be used for ocean
basin-scale studies such as the ATOC experiment (Baggeroer and Munk, 1992~.
The ATOC source level was thus reduced to 195 dB. This difference corresponds
to a 400-fold decrease in sound intensity. The 75-Hz ATOC signal was transmit-
ted from sources located at 850- and 980-m depths off the coasts of Hawaii and
California, respectively, for 20 minutes every 4 hours every fourth day, under the
standard protocol of a 2 percent duty cycle (see footnote on page 15~. This
standard protocol was varied somewhat in both the California and the Hawaii
transmissions, depending on the needs of MMRP investigators, although the
transmissions were not optimized for studies of marine mammals. The California
source transmitted for experimental periods of 2 to 4 days, separated by at least
4 days with no transmissions. The Kauai source used a similar protocol during
the first season, followed by the standard protocol of 1 day of transmissions every
4 days. One exception was that the duty cycle of the Kauai source was increased
to 8 percent in the summer of 1999, after the humpback whale season, in accor-
dance with the environmental impact statement (EIS) for the Kauai source (ARPA
and NOAA, 1995~.
21
OCR for page 22
22
MARINE MAMMALS AND LOW-FREQUENCY SOUND
For all ATOC transmissions, the source level in dB increased linearly from
165 to 195 dB and the power increased logarithmically over a period of 5 minutes
preceding the 20-minute, full-intensity transmission. This ramp-up period was
designed on the assumption that it would allow marine mammals the opportunity
to move away and avoid exposure to the sound if it annoyed them. ~ As a result
of the decrease in source level and the use of a sound ramp-up, the potential for
acoustic impact on marine mammals presumably has been reduced in ATOC
compared with HIFT. The sound level at the 850- to 980-m deep sources should
diminish to approximately 130 dB at the sea surface, plus or minus a small
fraction of this value due to the Lloyd mirror effect.2 Thus, marine mammals
that spend most of their time in surface waters potentially are exposed to much
lower received sound levels3 than the source level, although deep-diving species
could be exposed to higher levels when diving near the source. Geometric
spreading also diminishes sound levels in all directions from a source, so that the
received level is expected to be about 135 dB at a radial distance of 1 km from the
source and 129 dB at 2 km (see Figure 1.1~.
The Committee assessed all available information and concluded that the
Marine Mammal Research Program (MMRP) was not able to demonstrate a lack
of significant effects of ATOC transmissions on marine mammals. The MMRP
did not provide unequivocal evidence about the effects of ATOC transmissions
because (1) the MMRP data were not fully analyzed as of April 1999 and
(2) several of the observational programs were not designed in accordance with
the suggestions made in another NRC report (NRC, 1996) that may have helped
reduce the ambiguity of the results. It would have been impossible for the
MMRP program to conclusively demonstrate a lack of subtle or long-term effects
within the short period of the program and the program did produce some useful
results that advance our understanding of the effects of sound on marine mam-
mals. However, it is important for those designing future studies to recognize
that simply not detecting reactions is not by itself sufficient evidence that there is
no significant impact.
{Costa and Williams (1999) estimated that sustained swimming speeds of many marine mammals
are about 2 m/sec. Thus, the time needed for a marine mammal to swim from near the source to a
distance at which the received level would be 120 db (5.6 km) would be 47 min. The time needed to
reach the 130-dB received level distance (1.8 km) would be 15 min. Thus, the characteristics of the
ATOC signal ramp-up period could expose marine mammals to levels of sound of 130 to 165 dB for
periods of as much as 15 min.
2The Lloyd mirror effect creates a diminished or augmented pressure of sound from an under-
water source either located near the water-air boundary or when received near that boundary. It is
caused by the interference between direct and surface-reflected waves and thus creates alternating
sound nulls and peaks around this level.
3The "received level" is the sound pressure level measured at the animal, that is, the level to which
it is actually exposed. The received level is lower than the source level, depending on the distance
between the source and the animal, the sound frequency, and environmental factors.
OCR for page 23
EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
23
The MMRP was awarded $3 million to conduct its work over 5 years. The
Committee did not examine how this funding was allocated to different activities,
or whether the funding was adequate to meet the goals, staffing levels, or any
other management matters, so it is impossible to determine whether the program
was hampered by inadequate funding for the necessary tasks, poor planning and
execution of observations, constraints placed on the program by the ATOC experi-
mental design or regulatory requirements, the difficulty of working with large
whales, or other factors. Although the MMRP observations did show some
indications that the ATOC signal did not have a short-term effect on nearby
populations of marine mammals and there were no obvious mass mortalities of
marine mammals or abandonment of the ATOC source areas by marine mammal
species under observation, there was little detailed observational evidence of the
effect of the ATOC signal on individual whales. The MMRP results and the
committee's evaluation of the significance of the results are given in Table 2.1.
The Committee makes a number of recommendations in Chapter 5, based on
the MMRP experiences, about the need for peer-reviewed research, multidisci-
plinary research teams, proactive research programs not linked to specific acous-
tic experiments, and the need to devote sufficient financial and human resources
to ensure timely data analysis and publishing of results. Because the MMRP did
not provide unambiguous results about the effects (or lack thereof) of the ATOC
transmissions, the Committee cannot state unequivocally whether or not ATOC
transmissions should continue. (The Committee was not asked to make such an
assessment, but the question arose in the natural course of the Committee's
discussions.) Instead, in the event of ATOC continuation or other large-scale
acoustic tomography experiments, the Committee offers some criteria that should
be considered and some mitigation measures that may reduce concerns about
such experiments.
California ATOC Source
The goals of the California portion of the MMRP included (1) sampling the
distribution and abundance of marine mammals in the vicinity of the source,
(2) testing for differences in those distributions when the source was on and off,
and (3) measuring diving responses of a marine mammal (the northern elephant
seal, Mirounga angustirostris) as it passed the source while returning to its rook-
ery. Because of the distance of the source from land, shore-based observations
were precluded, so the distributions of marine mammals were sampled using
aerial surveys. Observations were also conducted from a small boat for photo-
graphic identification of humpback whales and blue whales and for enumeration
of other marine mammals. Aerial surveys provided a more or less synoptic
picture of whale distribution throughout the survey area in a single day. These
observations were designed to test whether the distribution of whales around the
sound source would differ when the source had been transmitting for 1 to 3 days,
OCR for page 24
24
MARINE MAMMALS AND LOW-FREQUENCY SOUND
TABLE 2.1 MMRP Experiments/Observations, Results, and Significance
Experiment/Observations Results
ATOC MI
California Results
Naturally migrating elephant seals
(Costa et al., 1999)
Translocated elephant seals
(Costa et al., 1999)
Distributions of marine mammals
by aerial observations
(Calambokidis, 1999)
Although the power of the test was low (or = 0.05;
power = 0.178), analysis of the five male seals
returning when the source was on (2-9 km) versus
the 11 control male seals (2-66 km) shows no
significant difference in closest distance to the
source (t = -1.524, df = 14, p = 0.15).
Data analysis is incomplete, but male seals exposed
to received levels ranging from 118 to 137 dB in the
60- to 90-Hz band did not seem to change their dive
patterns.
· A high diversity of species (including six endangered
marine mammal species) and numbers of individuals
was observed both when the ATOC source was on
and off.
Humpback whales within a 40 * 40 km inner box
centered around the ATOC source were sighted on
average 2.4 km farther from the sound source when
it was on versus off. No significant difference was
apparent in sightings of humpbacks in an 80 * 80 km
outer box excluding the inner box. Sperm whales
showed a similar response, but data are complicated
by dependence of clustered sightings of subgroups.
Risso's dolphins were also found farther from the
source in the experimental condition within 24 hours
of a transmission.
Behavior of marine mammals was generally similar
comparing exposure to control conditions. No
significant differences were observed in the
orientation of humpback and sperm whales, but
limited sightings of blue whales suggest they
oriented more toward the sound source during the
transmissions, a trend nearing the p = 0.05
significance level.
.
.
.
.
Althou
which l
appear
sound,
deviatil
resulted
ATOC
The fir
highest
seals in
was 13
The set
lack of
of the ~
even th
certain]
· No app
of sigh
exposu
statistic
in the (
While ]
the are;
some
near th
the sou
away (
OCR for page 25
EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
mce
25
ATOC MMRP Conclusion
NRC Committee Conclusion
= 0.05;
,eals
versus
no
the
, exposed
dB in the
their dive
ndangered
ndividuals
was on
per box
Bled on
roe when
ance was
;0 * 80 km
whales
mplicated
bgroups.
om the
n 24 hours
. ..
y slmllar
No
;, but
ey
ing the
· Although the one migrating seal for
which there was a dive record did not
appear to react to the initiation of the
sound, there does appear to be a
deviation in the dive pattern that
resulted from the cessation of the
ATOC transmission.
.
The first significant finding was that the
highest level of exposure to ATOC for
seals intentionally placed near the source
was 137 dB in the 60- to 90-Hz band.
· The second significant finding was the
lack of a dramatic response to operation
of the ATOC sound source in any seal,
even though the seals could almost
certainly hear the source.
· No apparent differences in number
of sightings comparing control and
exposure periods, but there were
statistically significant differences
in the distribution of some species.
· While humpback whales did not vacate
the area during ATOC transmissions,
some whales shifted from using areas
near the sound source (<14 km from
the source) to areas slightly farther
away (14-28 km from the source).
.
No evidence was obtained to indicate that
the ATOC source disrupts the geographic
locations of migrating elephant seals, but
the power of the test is limited by small
sample size and lack of data on female
seals. More data are needed on influence of
ATOC on dive patterns of migrating seals.
· These are the only data on possible effects
of ATOC on diving behavior. Statistical
procedures did not correct for multiple
tests; test results need to be reanalyzed
before final conclusions can be drawn.
Given the high diversity and number of
animals, and the possibility that the Pioneer
Seamount is a critical habitat area for
marine mammals, it is probably not a good
area for the ATOC source to be located for
decades of operation. ATOC has
discontinued transmissions from this source.
Not enough data are available to determine
whether most species showed avoidance or
attraction. Significant differences in
distance of humpback whales from the
source indicate an avoidance response, but
the scale of this response is small enough
that this is unlikely to impact availability
of habitat for the population.
Aerial survey data suggest possible vertical
avoidance response for some species. For
example, there is some evidence for
increased sightings of sperm whales during
exposure, indicating that exposed whales
might spend more time at the surface, a
potential vertical avoidance response, but
this was not studied in sperm whales in
greater detail.
continued
OCR for page 26
26
TABLE 2.1 Continued
MARINE MAMMALS AND LOW-FREQUENCY SOUND
Experiment/Observations Results
ATOC MI
Hawaii Results
Observations from shore stations
during ATOC transmissions
(Franker and Clark, l999a,b)
Observations from boats
during playbacks
(Franker and Clark, 1998a)
Results of bottom-mounted
recorders
(Franker and Clark, l999b)
· Analysis of whales observed near shore,
approximately 14 km from the ATOC source,
.
.
showed a statistically significant increase in the time
and distance between successive surfacings as a
function of estimated received level of ATOC
transmissions. These whales were exposed to levels
up to 130 dB in the 60- to 90-Hz band.
Analysis of sighting rates of inshore whales showed
slightly higher rates during control versus
transmission periods, but the difference was not
statistically significant. No difference was found in
the distance of whales from shore, but distance from
the source was not analyzed.
Only 11 of 50 playbacks exposed whales to received
levels >120 dB in the M-sequence band.a These
whales did not show a pronounced avoidance
response.
Two behavioral variables showed a significant
increase with increasing exposure: the distance
traveled and time taken between successive
surfacings.
No difference in the amount of energy in the band
of humpback song was detected comparing
20 minutes before transmission, during, and after
transmission, from one recorder placed offshore near
the ATOC source and four recorders placed inshore
near the main concentration of whales.
The dis
inshore
signific
· · ret
slgnlllc
that ins
receive
Whale
differ s
and pla
Overal]
M-seq~
be dete
biologi
respond
There
song pi
This do
stopper
to franc
average
There ~
. .
singing
from tt
OCR for page 27
EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
27
ATOC MMRP Conclusion
NRC Committee Conclusion
.
ce,
.n the time
s as a
OC
1 to levels
s showed
is not
, found in
ance from
received
These
ice
cant
ance
he band
d after
shore near
d inshore
.
.
The distribution and abundance of
inshore whales did not change
significantly, but there were
significant changes in diving behavior
that increased with increasing
received level, up to 130 dB.
Whale tracks and bearings did not
differ significantly between control
and playback conditions.
· Overall, subtle responses to
M-sequence playbacks could only
be detected statistically, but the
biological significance of these
responses is uncertain.
There was no change in received
song power in response to ATOC.
This does not mean that no whales
stopped or started singing in response
to transmissions but rather that the
average song level did not change.
There was no widespread change in
singing behavior or movement away
from the area.
.
.
· There is a data gap in testing for changes in
the distribution and abundance of whales
near the ATOC source. Given evidence for
changes in the diving behavior of whales
exposed to low levels far from the source,
there is a clear need to study changes in the
behavior of whales near the ATOC source
in order to evaluate the potential impact of
behavioral disruption. It is uncertain
whether a change in the time and distance
between surfacings is a biologically
meaningful measure of the effects of the
ATOC source.
The limited number of whales exposed to
received levels >120 dB limits the power
of overall tests.
The same behavioral responses were
observed in scaled playbacks as were
detected in the operation of ATOC. This
replication increases confidence in the
robustness of this response.
A comparison of total sound energy in the
band of humpback song power shows no
change just before, during, or after
exposure. This is a very crude response
measure, which would miss potentially
important responses (e.g., half of singers
stop, half double their source level). In
addition, much of the power in the "song
band" could stem from sources other than
humpback songs and this unmeasured
background would not be expected to
change in response to an ATOC
transmission. This dilutes the power of the
test. Details of the movement patterns and
songs of individual whales singing near the
source need to be studied before it will be
possible to evaluate the effect of ATOC on
singing whales fully. The appropriateness
and statistical power of this method were
not tested.
continued
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28
TABLE 2.1 Continued
MARINE MAMMALS AND LOW-FREQUENCY SOUND
Experiment/Observations Results ATOC MI
Results of aerial surveys
(Mobley et al., 1999)
.
Of five major areas in the Hawaiian Islands,
Kauai/Niihau had the second-highest number of
humpbacks sighted, after the four-island region west
of Maui, but Penguin Banks west of Molokai had the
highest density after corrections for observing effort.
An average of 5.3 humpbacks and 0.6 sperm whales
were sighted per survey during 1994 within 40 km
of the source location before ATOC transmission.
An average of 7.0 humpbacks and 0.75 sperm whales
were sighted per survey within 40 km of the source
during 1998 after the source was activated. This
higher rate in 1998 may reflect better sighting
conditions.
Humpbacks prefer water <200 m deep, but
30 percent were sighted in 200-2,000 m depths.
Mean distances from shore and from the source were
higher for humpback whales when the source was on,
but difference was not statistically significant.
.
For hu]
in dista
from sl
results,
not ope
operati
Sperm
· r
as inert
were fc
island
NOTE: The first two columns of the table were provided to Christopher Clark and Dan Costa for
review before the report was published.
aAn M-sequence signal is a phase-modulated tonal signal.
compared with after at least 4 days without ATOC transmissions. Acoustic
surveys also were planned by MMRP investigators, and acoustic measurements
were attempted using ATOC receivers. The planned acoustic surveys did not
yield any data because of the failure of deployed equipment.
The following null hypotheses were tested using aerial, visual, and acoustic
surveys (ARPA, 1995, p. C-12:
Ho There is no detectable difference in sighting rate, distribution, orientation,
general activity, or group size of different species (or groups of species) between
OCR for page 29
EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
29
ATOC MMRP Conclusion
NRC Committee Conclusion
.s,
per of
gion west
cat had the
ing effort.
m whales
n 40 km
. .
msslon.
rm whales
e source
. This
tiny
pths.
lurch were
roe was on,
ant.
.
.
For humpbacks no significant changes
in distance from source or distance
from shore were noted from the 1994
results, when the ATOC source was
not operating, to 1998, when it was
operating.
Sperm whales, previously described
as infrequent in Hawaiian waters,
were found offshore of all five
island regions.
· Humpback whales in Hawaii showed a
pattern of increased distance from the
source when it was operating (average =
19 km) compared to off (average = 17 km).
This difference, based on 28 exposure
sightings, was not statistically significant.
A similar pattern in California (16.9 km for
exposure versus 14.5 km for control), based
on 105 exposure sightings in the 40 * 40
km inner box, was highly statistically
significant. It is likely that humpbacks in
both places have similar responses, and that
difference in significance stems from
limited sample sizes in Hawaii. The
possible shift in distribution at great ranges
from the source suggests the need for a
behavioral study on responses to ATOC
signals targeting animals near the source.
· Kauai is an important habitat for the
expanding population of humpback whales
wintering in Hawaii. Coarse analysis does
not suggest a mass evacuation of the area
within 40 km of the ATOC source.
However, enough humpbacks were sighted
in water >200 m depth to justify a
targeted study of humpbacks near the Kauai
source location. The presence of offshore
sperm whales also suggests that a targeted
study on the impacts of long-term ATOC
signals on this endangered species would
be appropriate.
n Costa for
surveys conducted when the source is on and when it is off, and as a function of
distance from the source.
Ho There is no detectable difference in cetacean acoustic behavior (i.e., call
types, rates, structure, or sequence patterns) between measurements from record-
ings made when the source is on and when it is off, and as a function of distance
from the source.
Appropriate tests of these hypotheses assume that the precision of the mea-
surements and the statistical power of the tests are great enough to demonstrate
OCR for page 30
30
MARINE MAMMALS AND LOW-FREQUENCY SOUND
actual differences; that is, the probability of a false negative result is small.
Studies of marine mammals in the wild are so difficult (due to problems of
observing animals that spend much of their time underwater) and the results so
imprecise (because of natural variability and low sample sizes) that it is easy to
imagine that such studies might not detect differences that could reflect biologi-
cally significant impacts. Only for tagged elephant seals exposed to California
transmissions were analyses of precision or power presented, and thresholds for
biological significance were not suggested. These factors make it difficult to
evaluate the validity of the MMRP's negative results, especially for species other
than elephant seals.
Aerial surveys were conducted from November 1995 to October 1998. Dur-
ing control surveys there were 1,524 marine mammal sightings4 involving 29,826
animals. During experimental surveys (source on), there were 1,617 marine
mammal sightings, involving 27,874 animals. Not only were there more sightings
in both the experimental and the control conditions than expected, there was a
larger diversity of marine mammals sighted than expected. At least eight species
of small- and medium-sized toothed whales were observed, four species of seals,
five baleen whale species, and two species of large toothed whales. The most
frequently sighted large whales were humpback whales (482 sightings) and sperm
whales (349 sightings), numbers large enough to permit statistical tests for differ-
ences between control and experimental surveys. Statistical analyses of these
data were not completed by the time of the Committee's April 1999 meeting.
Aerial surveys revealed that humpback whales were significantly further from
the source when it was on than when it was off. A similar pattern was found for
sperm whales, but the statistical significance was complicated by seasonal differ-
ences in distribution (Calambokidis, l999~. Calambokidis also found an increas-
ing trend in the number of humpback whales off the U.S. west coast from 1988 to
1996 (6.7 percent) and from 1996 to 1998 (9.3 percent), using photoidentified
whales and mark-recapture calculations, indicating that the ATOC source did not
negatively affect the population level of this species.
Elephant seals are important research subjects in relation to the effects of the
ATOC source because they have sensitive low-frequency hearing (Kastak and
Schusterman, 1998), swim in the pelagic zone, and routinely dive near the depth
of the deep sound channel.5 This species has breeding areas near the California
ATOC source site, and these animals are excellent subjects for tag attachment
(tags are subsequently removed or shed during molting; D. Costa, University of
4A sighting is one group of marine mammals, regardless of number.
5The deep sound channel or SOFAR (Sound Fixing And Ranging) channel occurs at a depth in the
ocean at which ``sound rays propagating close to horizontally are trapped by refraction, reducing
spreading loss and avoiding surface and bottom losses,, (Richardson et al., 1995). The SOFAR
channel is found at approximately 1,000 m in the open ocean and approaches the sea surface in polar
regions.
OCR for page 31
EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
31
California, Santa Cruz, personal communication, 1999~. Satellite tags were used
to track the locations of naturally migrating individuals. A total of 26 adult males
were followed during their natural migration; five tracks were observed when the
source was on, and 11 tracks were monitored when the source was off. Only a
few tracks of these naturally migrating seals passed near the ATOC source, and
there was no obvious avoidance, based on nearest approach to the ATOC source.
Based on aerial surveys, elephant seals were found at the same distance from the
source whether the source was on (50 sightings) or off (35 sightings).
Translocation experiments were used to obtain a larger sample size of seals
exposed near the source. In these experiments, archival tags designed to record
received levels of sound and dive patterns were attached to juvenile elephant
seals removed from a rookery. Thirteen elephant seals were translocated near the
ATOC source when the source was operating, and five seals were translocated to
the same site when the source was off. The maximum measured received levels
of the ATOC sound for each of the 13 seals in this experiment ranged from 118 to
137 dB. MMRP investigators conducted an extensive statistical analysis of dive
patterns of the translocated seals (including a variety of measures, such as time of
dive and depth) comparing (1) the dive before the source was turned on, (2) the
first dive that started after the source was turned on, (3) the second dive after the
source was turned off, and (4) an average of dives measured over 18 hours
following the second dive after the source was turned off. The comparisons
conducted thus far suggest that there was not a statistically significant change in
the dive behavior of translocated seals in response to ATOC transmissions at
received levels of 118 to 137 dB. However, the preliminary statistical analysis
comprised hundreds of individual tests. These must be merged into one overall
analysis, with proper correction for significant results that can occur by chance
when a large number of statistical tests are run.
Hawaii ATOC Source
The Hawaiian observations focused on humpback whales and were planned
to include aerial visual surveys, passive acoustic monitoring, and shore-based
surveys of reactions to ATOC transmissions (off Kauai) and playbacks of hump-
back whale vocalizations (off Hawaii). The only peer-reviewed paper analyzing
the responses of marine mammals to the ATOC signal to date is that of Frankel
and Clark (1998a). This paper did not report on research involving the ATOC
source in its site off the north coast of Kauai but described a series of playback
experiments using a smaller vessel-deployed source off the coast of Hawaii in a
much better site for observing whales. This source was operated at 172 dB, with
a frequency bandwidth of 60 to 90 Hz (the same as ATOC). The source was a
vessel moored each day in an area of high whale density off the leeward coast of
Hawaii, in a position allowing excellent monitoring of humpback whales from a
shore station. Unlike most MMRP observations, timing of operation of the
OCR for page 32
32
MARINE MAMMALS AND LOW-FREQUENCY SOUND
source was determined by whale monitoring rather than the predetermined ATOC
transmission schedule. In this study, if the shore observers could follow a whale
or group of whales for 25 minutes, they would radio the playback vessel and
instruct the boat to start an experiment. On a randomized schedule, during 50 of
the 85 trials the vessel transmitted the ATOC signal; the other 35 trials were no-
sound controls. The shore observers were unaware of which condition was being
employed during any given trial. The shore team attempted to continue to ob-
serve the whales during the 25-minute experimental period and for a 25-minute
post-trial phase. The estimated received level (based on empirical measurements
at different ranges and bearings from the playback vessel) at the whales' location
during playback varied from ambient (near 90 dB) to nearly 130 dB.
Statistical analyses of whale tracks and swimming directions revealed no
difference in these factors between experimental and control conditions. How-
ever, this is difficult to interpret because the analysis combined data from whales
located so far from the playback signal that the signal was buried in ambient
noise, with only a few whales exposed to received levels high enough to expect
the possibility of a response. Simple nonparametric comparisons of speed, dura-
tion, and distance between surfacings of the humpback whales also showed no
difference between control and playback conditions. It appears that the swim-
ming direction of whales with respect to the playback source was not analyzed,
even though this is the critical measure for determining an avoidance response.
There was a slight significant increase in the time and distance between succes-
sive surfacings at increasing received levels of playback; this strengthens the
Committee's concerns about conclusions of no effect in these pooled data. Of the
85 trials, an observed whale passed within the 120-dB isopleth at a range of about
400 m in 11 playback trials and five control trials. A potential avoidance reaction
was observed in one of these 11 playback trials; a similar "avoidance reaction"
also was observed during control observations with no sound. Two potential
approaches were observed during playback. The limited sample size of animals
exposed to received levels greater than 120 dB limits the power of conclusions
regarding lack of effects.
Although the sample size of whales exposed to playbacks louder than a
120-dB received level was small, the results imply that most whales would be
unlikely to show an avoidance response when exposed to sound levels of 90 to
130 dB. The responses observed were no stronger than those elicited when
vessels approached whales in the study area.
The Committee received several unpublished manuscripts from MMRP
investigators about the responses (or lack thereof) of humpback whales to the
ATOC source 14 km north of Kauai's coast. The Committee was told that aerial
survey results suggested there may be resident populations of sperm whales and
short-finned pilot whales (Globicephala macrorhynchus) in the offshore waters,
but the Committee was not presented with any data on the distribution or potential
responses of these two species when exposed to the ATOC sound. Rather,
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EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
33
MMRP studies concentrated on humpback whales, as indicated in the EIS for the
Kauai source (ARPA and NOAA, 1995~. The observation effort focused on
inshore waters roughly 10 km from the source. Transmission loss measurements
suggest that the received level of the ATOC signal in the inshore waters preferred
by humpback whales (less than 200 m deep) is less than 120 dB in the 60- to 90-Hz
frequency range.6 Although many analyses found no difference in responses
between control and transmission conditions, some statistically significant differ-
ences apparently were observed, even though most whales appeared to be exposed
to levels less than 120 dB. As in the playback experiments off the island of
Hawaii, the distance between successive surfacings increased with increasing
received level of ATOC transmissions off Kauai during 1998 (p = 0.0017~. This
could have resulted if the whales either were swimming faster or stayed under
water longer between surfacings.
The Quick-Look Report of the Hawaii ATOC-MMRP (Franker and Clark,
1998b) (an unpublished and unreviewed account)7 concluded that "there were no
acute or short-term effects of the ATOC transmissions on marine mammals."8
The Committee questions whether a conclusion this broad can be reached at this
time using the data provided. The report does, in fact, present evidence for some
short-term behavioral changes in response to the ATOC sound source by hump-
back whales. Even more important, the Committee questions the ability of the
MMRP to show the absence of any response. The failure to observe an effect
could result from a number of factors, including the specific conditions of the
experiment and lack of sufficient statistical power (resulting from an insufficient
number of observations or the statistical test chosen). This concern is particularly
heightened for the Hawaii MMRP study in which most observations were made
far from the source and no results were presented on responses of the marine
mammal species most commonly sighted offshore near the source (sperm whales
and pilot whales).
Contrary to plans listed in the EIS for the Kauai source (ARPA and NOAA,
6The original predictions in the initial EIS were based on a spherical transmission loss from the
20*1Og(range) relationship. That is how the 40-km radius "zone of influence" was determined. This
contour is approximately 7.5 km south of the ATOC source. Actual measurements of the ATOC
transmissions found that the 120-dB received level occurred approximately 4.8 km south of the
source. At the 200-m contour, the received level was approximately 111 dB in the 60- to 90-Hz
ATOC band (C. Clark, Cornell University, personal communication, 1999). This was more consis-
tent with the predictions of a cylindrical equation model, which terminated the 120-dB isopleth at the
200-m depth contour.
7The Quick-Look reports were undoubtedly designed as a means to disseminate research results
rapidly and widely to try to achieve open access to research results and keep the public informed,
both worthy goals. However, the Committee determined that the Quick-Look format was generally
counter-productive because it widely disseminated non-peer-reviewed results and did not encourage
timely peer review and publication of research results.
8http://atoc.ucsd.edu/HIquicklookrpt.html, accessed 10/13/99.
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MARINE MAMMALS AND LOW-FREQUENCY SOUND
1995), there were no analyses of the vocal behavior of individual humpback
whales exposed to the ATOC signal. Instead, there was only a general assess-
ment of the total energy at humpback whale vocalization frequencies in the area,
which could be misleading given that all vocal activity in the area was summed
for pro- and postexposure. Considering the analyses conducted to date, the
possibility that the ATOC signal might affect the song production of humpback
whales cannot be eliminated. We do not know the functions) of humpback
songs, but they may be a reproductive "advertisement" display, as for the songs
of some birds (Tyack, 1981~.
The limited data presented by the MMRP made it impossible to draw any but
the most tentative conclusions about the effects of ATOC sounds. Based on the
material presented, baleen whales, sperm whales, and elephant seals in California,
and humpback whales in Hawaii did not show profound avoidance responses to
the ATOC signal. However, complete analyses and peer review are required
before any more definitive conclusions can be reached.
COMPARISON OF THE RECOMMENDATIONS OF NRC (1996)
AND MMRP RESPONSES
Although it was difficult to evaluate the MMRP in midcourse, the 1996 NRC
interim report contained the following conclusions:
The California ATOC source transmissions did not appear to cause a
major change in the distribution of marine mammals.
2. The constrained sound characteristics and conditions used during the
MMRP-controlled ATOC transmissions impeded the project's ability to answer
fundamental questions concerning the impact of ATOC-like noises on marine
mammals.
3. Several changes in the plans for the Hawaiian MMRP studies (eventually
concluded in 1998) could provide more definitive information about the potential
of ATOC sound to affect marine mammals and other organisms. Specifically,
shore-based observations should be conducted for the entire 6 months of ATOC
transmissions, and the effectiveness of observational methods should be vali-
dated using playbacks of relevant natural sounds conducted within visual range
of the shore station.
The Committee reviewed plans for MMRP research in its 1996 interim report
and believed that the value of the work could have been enhanced considerably
with some modifications in the proposed study. Not only would these changes
have strengthened the ability of the MMRP to test the effects of the ATOC sound
on marine organisms, the additional data obtained would provide useful insight
into broader questions about the effects of low-frequency sounds on marine mam-
mal behavior. Much of the MMRP research focused on statistical tests of whether
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EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
35
behavioral indicators varied significantly between transmission and control con-
ditions. The Committee favored tests in which the biological significance of any
such changes could be evaluated, which would require a broader investigation
into the effects of noise on the normal behavioral ecology of each species.
The goal of the MMRP was to determine whether the ATOC transmissions
might adversely affect reproduction or survival of marine mammal populations.
The methods available to measure population trends are crude, and the cause of
conserving populations will not be met by waiting until a threat actually causes a
measurable decline in populations. Therefore, it is useful to use more short-term
measures as indicators of potential adverse impact. For example, if marine
animals avoid or leave critical habitats because of a human disturbance, the
animals may enter suboptimal habitats, with eventual negative effects on feeding
and/or reproduction. Proxies selected to measure adverse impact should be easily
measured animal behaviors that, if disrupted, would have significant negative
impacts on marine mammal reproduction and longevity. The apparent avoidance
reactions observed in the California MMRP studies are good examples of rel-
evant measures; the impact can be related to the percentage of habitat lost or can
be estimated by comparing the quality of the habitat the whales left compared to
that to which they moved.
Other elements of the MMRP studied behavioral changes that are less rel-
evant. For example, the Hawaii MMRP analyzed the distance traveled and time
spent between surfacings for humpback whales and found a statistically signifi-
cant trend for these measures to increase with increasing exposure to ATOC
transmissions. Even though these results are statistically significant, it is difficult
to interpret their possible biological significance. We suggest that future studies
of this sort carefully select behavioral and physiological measures that can more
easily be related to potential adverse impact. Basic research in the behavioral
ecology of many species is required to direct these choices. For example, the
more we know about the foraging ecology of a species, the better we can interpret
the biological significance of disruption of feeding behavior, or movement to
different feeding areas. Since humpback song is known to be involved in the
breeding behavior of humpback whales and the ATOC sound could have disrupted
singing, the Hawaii MMRP observations would have benefited from selecting
behavioral studies that could more easily be related to potential impact on song
and thus breeding behavior.
NRC (1996) offered two suggestions and one point for further consideration.
The first suggestion concerned maintenance of the onshore observation station on
Kauai for the full duration of source testing to allow time for additional playback
experiments. The second suggestion concerned the need for prompt analysis and
dissemination of MMRP results. An additional point concerned other marine
species that are potentially ensonified by ATOC sounds. For each of these issues
the following sections will present recommendations of the NRC from its 1996
interim report, followed by the MMRP responses.
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MARINE MAMMALS AND LOW-FREQUENCY SOUND
Maintenance of the Shore Station and Playback Experiments
At its October 1996 meeting the Committee was presented with plans for
maintenance of the shore observation station at the Hawaii field site during the
1997 ATOC transmissions to observe behavioral changes in humpback whales
during exposure to ATOC sounds. Observation of marine mammals from similar
shore stations provided useful baseline data during a previous playback study of
humpback whales off the coast of the island of Hawaii (ARPA and NOAA, 1995,
Appendix G) during the 1993 to 1994 season and earlier off the coast of California
(Malme et al., 1983, 1984~. According to plans for the ATOC sound transmis-
sions in 1997, the shore station observers were to be in place for only 4 to 6
weeks. This period was designed to provide the minimum amount of information
needed for comparison with the 1993 to 1994 baseline data, with no margin for
unforeseen circumstances.
The Committee disagreed with this minimal effort and recommended that
the shore station be maintained and used throughout the humpback whale season
off Kauai (e.g., during the entire 6 months of MMRP-controlled ATOC transmis-
sions). This suggestion was based on the conclusion that additional very useful
data (see below) could be obtained from continuation of the shore-based observa-
tions, especially with the addition of natural sound playbacks near the shore
station. Extending the field season also would have increased the sample size of
observations, making it more likely that significant effects of the ATOC trans-
missions would have been detected, if such effects actually occurred. Shore-
based observations are important because they provide a means of observing
marine mammals without introducing the confounding effects of nearby vessels.
Although the shore site was probably outside the area within which an effect
would be expected, such observations should have been able to determine whether
inshore humpback whales, rather than offshore near the ATOC source, would be
affected. The MMRP did conduct shore observations for 6 weeks from Febru-
ary 9 to March 20, 1998. Observations were not extended beyond this time.
According to the MMRP, as of 1996, ATOC transmissions in California and
an ATOC-like test signal played off Hawaii had little observed effect on marine
mammal behavior, at least in terms of surface tracks and the number, frequency,
or depth of dives. Interpretation of these findings is complicated, however,
because there had been no observed response to ATOC signals. Thus, it was
impossible to establish the validity of the method that had been used to study
ATOC's effects. Simply stated, the Committee could not choose between the
conclusion that the ATOC signal had little or no effect and the alternative view
that the observational methods used were not sensitive enough, or not designed
appropriately, to detect the effects of these sounds. In the interest of facilitating
future investigations into the effects of ATOC or ATOC-like sound sources on
marine mammals, it is essential that an effort be made to define protocols that are
useful scientifically and relevant to the decisions that must be made. Such proto-
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EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
37
cots could specify how observers must confirm before their observation program
begins that their observation techniques can measure the variables of interest-
behavior associated with critical activity as well as the minimum statistical
power that can be tolerated, so that significance of disruption can be ascertained.
Analyses should be framed not only to test for any detectable change, but also to
estimate the percentage of time a behavior is disrupted, the amount of energy
wasted, and/or the probability that the disruption will prevent animals from
achieving the goal of the activity.
The Committee's dilemma could have been overcome if the MMRP had
been able to demonstrate that its observation methods were valid. The most
direct means to test the methods would have been to increase the intensity of the
sound source until a response was observed, to create a direct estimation of the
stimulus-to-response relationship. However, the ATOC source cannot be oper-
ated at levels higher than 195 dB for technical reasons, and it is unknown whether
higher levels would produce a measurable response without being unduly harm-
ful to marine mammals. Therefore, the Committee suggested an alternative
approach that of broadcasting noises other than ATOC signals that would affect
marine mammal behavior in a way that is detectable by the same (or similar)
methods used in the ATOC study. In earlier studies of marine mammal responses
to playback of auditory stimuli, Clark and others (Clark and Clark, 1980; Malme
et al., 1983; Tyack, 1983; Mobley et al., 1988; Frankel et al., 1995) have shown
that animals respond strongly to certain natural vocalizations, such as the calls
given by other members of the same species or the vocalizations of a predator,
such as the killer whale (Orcinus orca).
Although use of a non-ATOC stimulus would not allow validation of the
specific response to the ATOC stimulus, it would at least have validated that
MMRP investigators could observe (with sufficient precision and accuracy) such
things as startle, flight, and vocal responses, which could be produced by many
different stimuli, whether ATOC sounds or killer whale calls. The Committee
recommended that the MMRP incorporate natural sounds into its research during
its 1997 to 1998 studies, taking into account the results of the playback studies
cited above. The MMRP did not conduct extensive vessel-based playbacks of
natural sounds, although a vessel was used during this time to observe whales.
Frankel and Clark (1998a) reported on one playback of an Alaskan humpback
whale feeding call, although the results were ambiguous. If playback of these
natural sounds had elicited a strong observable behavioral response from the
subjects, that response would have provided an important validation for the ob-
servational method used by the MMRP to test ATOC's effects on the behavior of
marine mammals. Measurement techniques must be calibrated with a stimulus
that produces a measurable response. Such a calibration allows a scientist to
distinguish between a true lack of response and a response that was unmeasurable
by the chosen technique. For example, in the case of singing humpback whales,
had the researchers tested enough singing animals with a biological sound (e.g.,
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MARINE MAMMALS AND LOW-FREQUENCY SOUND
killer whale vocalizations), they could have determined which behavioral param-
eters showed statistically significant changes (e.g., song elements, diving behav-
ior, evacuation of the area) and provided a baseline of comparison for other
stimuli. Because the MMRP did not add this component, the difficulty of inter-
preting the MMRP' s results remains.
Changes that might have indicated significant effects of ATOC transmis-
sions include
· significant changes in singing patterns (would need to correlate with
calving rates);
· significant flight of animals from the source area (significant either in
distance, speed, duration, or movement into harm's way);
· significant reduction in calves produced; and/or
· significant abandonment of area by identified individuals in later years.
Need for Prompt Data Analysis
One of the problems faced in preparation of the 1996 NRC report was the
lack of analyzed data from a number of MMRP field studies, particularly those
conducted in Hawaii. Thus, it was difficult to assess the quality and significance
of this work and to make suggestions for future ATOC-related marine mammal
studies. In its 1996 report the NRC noted that such a situation, if it persisted,
would compromise the Committee's future work, and it would not be able to
conclude whether there are deleterious effects of the ATOC sound source on
marine mammals (or other organisms). The Committee expressed its hope that it
would receive a full analysis of MMRP observations and conclusions at least 2
months prior to its final meeting. The NRC strongly recommended that data
analysis and presentation be the highest priority for investigators in both Hawaii
and California and that sufficient funds be set aside to enable a complete and
expeditious evaluation of the data. The Committee's 1999 meeting was sched-
uled for approximately 6 months after completion of MMRP observations to
allow time for analysis to be completed. The Committee received the June 1998
Quick-Look Report on the Hawaii ATOC-MMRP Results several weeks before
its April 1999 meeting. This Quick-Look Report included some preliminary
analyses and indicated that more extensive analyses would be forthcoming. The
Committee did not receive any completed analyses or conclusions before the
meeting. The MMRP investigators at the meeting asserted (as did the Quick-
Look Report) that considerable further analysis was needed to interpret the data
properly. In discussions with MMRP investigators during the April 1999 meet-
ing, it was clear that only limited funds and personnel were available during the
final year of the MMRP and that this shortage continues to jeopardize the quality
and timeliness of the scientific products of the MMRP.
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EVALUATION OF THE MARINE MAMMAL RESEARCH PROGRAM
Ensonified Species Other than Marine Mammals
39
In addition to the two specific suggestions for MMRP research, the Com-
mittee noted that the EIS for both the Hawaii and the California sources included
analyses of the effects of the ATOC sound on other biota, including marine
turtles, fish, and other organisms (ARPA, 1995; ARPA and NOAA, 1995~. The
only study published for other vertebrates from ATOC-funded research was for
an experimental study of ATOC-like sounds on fish (Klimley and Beavers, 1998~.
The NRC (1994, pp.53-53) specifically pointed out that a major concern for
all low-frequency ensonification is not only effects on marine mammals but also
the potential effects of such sounds on other components of marine mammal food
chains, such as fish or zooplankton, and on other endangered species (e.g., turtles).
The Committee strongly supports this assertion and continues to be concerned
that low-frequency sound may have implications for a far wider range of the
marine biota than is being studied at the moment. This is of particular importance
for sound sources such as ATOC that will be operated in one place for years at a
time. In addition, a number of studies suggest that ATOC-like sounds may be
very attractive to many species of sharks (Myrberg, 1972, 1978; Myrberg et al.,
1976~. Sharks attracted to ATOC sounds could be affected adversely by these
sounds, and ATOC equipment could be jeopardized by sharks. The lack of study
on marine organisms other than mammals makes it impossible to infer the poten-
tial impact of long-term deployment of ATOC-like sources in areas used by
. . .
sensitive species.
SIGNIFICANCE OF THE MMRP TO RESEARCH USES OF SOUND
Data presented by the MMRP were inconclusive regarding the effects of the
ATOC sound on marine mammals. The Committee considers that existing data
from the MMRP and other sources such as recent work motivated by the 1994
NRC report and funded by ONR (e.g., Au et al., 1997) suggest, however, that
there is no cause for alarm about the short-term effects of ATOC sources on
dolphins and most seals because they do not dive to depths that would allow them
to encounter the source at levels they could hear well. However, there is cause
for concern because we cannot totally rule out short- and long-term effects of
ATOC, particularly on baleen whales and sperm whales. Optimally designed
studies are needed on the long-term effects of high-intensity sound sources (e.g.,
interference with communication and reproductive activities, exclusion from
critical habitat).
ATOC investigators plan to apply for funding and permission to continue
ATOC transmissions in Hawaii for another 5 years (the California source has
been terminated). ATOC investigators plan to conduct aerial surveys near the
Kauai ATOC source to monitor the distribution and abundance of marine mam-
mals to advance the understanding of possible long-term acoustic impacts (P.
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MARINE MAMMALS AND LOW-FREQUENCY SOUND
Worcester, Scripps Institution of Oceanography, personal communication, 1999~.
It is outside the Committee's charge to comment on whether ATOC should be
allowed to proceed. However, if it does proceed, monitoring of marine mammal
behavior and responses to the ATOC transmissions should continue as an integral
part of the experimental design in order to improve the ability to evaluate the
impact of ATOC during the next 5 years of Hawaii ATOC transmissions. As part
of this continued evaluation, there should be annual reports of all yearly data to
an oversight body not associated with ATOC (e.g., the Marine Mammal Com-
mission or National Oceanic and Atmospheric Administration), with the authority
to terminate transmissions if there is evidence of significant deleterious effects
from long-term exposure. ATOC scientists should be required to notify the
oversight group immediately if they detect significant adverse effects on marine
mammals. Continuation of ATOC transmissions should be conditional on timely
publication of marine mammal results. Chapter 5 includes a discussion of appro-
priate monitoring that should be considered if ATOC is approved to continue.
Representative terms from entire chapter:
marine mammal
