marine mammal surveys. The workshop report is now available;
an executive summary is below. An on-line copy of the report
may be found at
<a
href="http://www.pmel.noaa.gov/vents/acoustics/pdfs/AcousticAssessmentWorkshopRepo";
rel="nofollow">http://www.pmel.noaa.gov/vents/acoustics/pdfs/AcousticAssessmentWorkshopRepo</a>
rt.pdf
If this link is split across two lines, you will need to paste it
together to make it work.
If you would like a printed copy of the report, please let me
know.
Dave Mellinger
[EMAIL PROTECTED]
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Future Directions for Acoustic Marine Mammal Surveys:
Stock Assessment and Habitat Use
Report of a workshop held Nov. 21-23, 2002,
Southwest Fisheries Science Center, NOAA Fisheries, San Diego, CA.
Executive Summary
-----------------
Current uses of acoustics:
Acoustic survey methods are now used primarily to augment visual
sighting methods. During line-transect surveys, acoustic observers who
monitor towed hydrophone arrays routinely detect more groups of
animals than visual observers. In some cases, acoustic detections are
being used to make more accurate estimates of marine mammal
populations than would be possible with visual methods
alone. Autonomous recorders are cost effective for use in regions that
are difficult or expensive to reach, such as Antarctica, the Indian
Ocean, and areas far offshore in the Atlantic and Pacific Oceans, and
they are effective for seasonal coverage when visual surveys are not
feasible. They may also be useful to survey areas infrequently
occupied by marine mammals, where routine visual surveys would have a
very high cost per sighting.
Future uses of acoustics:
Acoustics holds eventual promise of gathering information about marine
mammals at very low cost. Research is needed in several areas to
realize this possibility. Discussion at the workshop centered on these
broad categories:
1. Population structure. If acoustic differences between
populations of marine mammals are tied to genetic differences,
then acoustics would offer a relatively fast and inexpensive
method to assess population structure. The foremost research need
is to determine the relationship between the population structures
as indicated by acoustics and by genetics.
2. Abundance and density. Acoustic observation can complement
visual observation to provide more accurate estimates of marine
mammal populations. This has been done for some populations, as
for example the Bering-Beaufort-Chukchi Sea stock of bowhead
whales and the eastern Pacific stock of sperm whales, but it could
be done more widely. For effective acoustic censuses, calibration
methods must be determined by joint visual-acoustic studies;
determining such factors offers the promise of low-cost surveys
for many species of marine mammals using acoustic
methods. Research is also needed in acoustic species
identification, particularly for smaller odontocetes.
3. Impacts of noise. Responses of marine mammal to natural noise
have not been well studied. Natural noise can include sounds of
other marine mammals, especially conspecifics, as well as physical
noise sources such as from geological sound sources and
wind. Responses of marine mammals to anthropogenic noise was seen
as a topic well covered by other work; discussion here was limited
to the contribution that passive acoustics can make. Assisting in
the constructing of an "ocean noise map" was strongly supported,
as was better public communication of information on ocean noise
levels.
4. Relative density, seasonal distribution, and trends. For
determining relative density or abundance, and trends in
abundance, many of the same calibration factors are needed as for
determining absolute abundance. But in the absence of those
calibration factors, acoustic methods can offer estimates of
minimum population size, and can be used to track large-scale
movement patterns.
Workshop discussion culminated in a list of recommendations for management,
research, and field operations.
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