Summary and Recommendations
In addition to the recommendations documented in the individual working group reports, several
common themes evolved from the meeting.
- It was recognized that development, acquisition, and use of new sampling technology was
needed to successfully address GLOBEC science issues. Acoustical and optical technologies were
acknowledged as leading candidates from which the necessary tools could be drawn to support the
pursuit of GLOBEC's science goals.
- Based on their quasi-continuous sampling characteristics, acoustical and optical tools
deployed in various ways (e.g., towed or hull-mounted sensors vs. moored, bottom-mounted, or
drifting sensors) are essential to relating small-scale processes important at the level of the individual to
large-scale processes that impact populations. This concept was described as "nesting" of sensors that
measure small-scale temporal and spatial phenomena within measurements at incrementally increasing
temporal and spatial scales up to those that include populations and their dynamics.
- Several groups stressed the importance of the mode of deployment of any acoustical, optical,
or integrated sensor package. The same mode is not, in general, appropriate for all the different kinds
of GLOBEC science questions. The ability to use an instrument in a diversity of deployment modes,
e.g., cast, towed, hull-mounted, bottom-moored, etc., was considered a valuable sensor
characteristic, substantially enhancing the usefulness of a particular instrument.
- Each of the working groups recognized the value of examining the same distribution of
animals with more than one frequency of sound. It was recognized that the range and numbers of
frequencies required depends on the sizes of the animals present, which animals present are of interest,
their abundances, their physical characteristics, their distribution, and the mode in which the sensor is
to be used.
- Several groups noted that modularity, standardization of instrumentation, and simplicity of
operation and deployment were important. At the same time, arguments for versatility, flexibility in
deployment mode and signal processing algorithms, sophisticated internal data processing, and low
cost were presented. On the surface some of these criteria seem conflicting, thus requiring thoughtful
tradeoffs when designing instrumentation.
- It was determined that the integration of acoustical and optical technology could yield
synergistic benefits and that the technologies are complementary. Acoustic sensors could place optical
measurements in the context of larger scale biological distributions. They may also be used to detect
rare organisms that may prey on the relatively small and more numerous animals under study with the
optical system. Acoustic sensors could also contribute data on vertical migration and swimming
behavior to aid in better understanding optical observations. Optical data could provide important
measurements of animal orientation, provide independent information on particle size spectra, and
offer a potential for taxonomic identification of acoustically sensed individuals and distributions (e.g.,
aggregations, schools, patches, layers).
- There was a strong sense that sampling of both the biological environment (e.g., with
acoustics and/or optics) and the physical environment (temperature, salinity, light, currents,
turbulence, etc.) should be done synoptically rather than serially. There was also a sense that
traditional methods will remain important in sampling the marine environment, but that the use of
alternative sensors will result in major improvements in the efficiency of these conventional sampling
tools.
- The establishment of data archiving protocols to facilitate long term (10's of years) use of
data is explicitly recognized as a particular problem for acoustical data as it is for GLOBEC data in
general.
- In some cases, access by the community of biological oceanographers to complex
bioacoustic instrumentation is limited by acquisition cost and the multidisciplinary talents (electronics,
acoustics, and machine level programming) required to operate, calibrate, adapt, and maintain such
gear. The establishment and staffing of a limited number of "facilities" or "teams" to provide and
maintain bioacoustic devices for data collection under the direction of individual or groups of
investigators, is recognized as a viable approach to expansion of the biological communities' access to
such devices.
- Finally, there was a consensus that there was a need for continued basic research and
development in order to advance the state-of-the-art in remote underwater sensing of marine animals.
Specifically, advances would be welcomed in the following areas:
- Development of new methods for quantitative combination of multifrequency acoustic data;
- Continued analytical research and supporting measurements directed towards the
development of better and more comprehensive descriptions of acoustic scattering from all marine
genera (e.g., adult fish, larval fish, micronekton, macrozooplankton and small zooplankton); and
- Development and validation of methods for quantitative combination of multisensor data
(i.e., data fusion).