Rapid characterization/mapping of
shelf seabed habitats and measuring the dynamics of large sessile seabed
with quantitative video
C. Roland Pitcher, Ph.D.
CSIRO Division of Marine Research
Wednesday, October 4, 2000
3:00 p.m.—Pacific Forum
Management and conservation of Australia's Exclusive Economic Zone
requires information on distribution and abundance of its resources and
biodiversity. We have been providing such information for large areas of
tropical NE continental shelf. Our approach is (1) to cover broad spatial
scales intensively by characterizing many sites rapidly, and (2) to
measure longer-term dynamics at key sites.
For (1), we use a suite of simultaneous rapid deployment methods,
including video camera transects (with acoustics), side-scan sonar,
benthic dredge, and sediment grab, as appropriate. The position of the
remote camera is tracked by an acoustic tracking system. Acquired data
(vessel position & heading, tracking range, bearing & depth, VCR
tape position, etc.) are integrated by a computer logging system that
writes all data to a database and key information onto the video image.
Semi-quantitative physical and biological characterization of the video
are entered in real time (1 Hz). On-deck processing yields dredge catch
and megafauna biomass and qualitative sediment classification. These data
are immediately available for applications, e.g. GIS, for presentation as
maps. The video & biotic samples are retained, providing capacity for
detailed enumeration and mensuration as required. Typically, sites are
located on a <5 to >10 km grid, depending on the complexity of
For (2), other devices such as ROVs, SSBA (where shallow) may be used
2-laser scaled video systems to provide more detailed information from
particular sites or, where repeated visits are required, to sites or to
individual sessile organisms. Positioning and other acquired data are
logged as above. Individual organisms may be tagged with RF-transponders
and tag-IDs automatically linked to a database of previous images. Fauna
at sites are carefully observed, mapped, identified & measured for
growth, condition, and mortality. The usage of living epibenthic habitat
by key finfish species is also observed.
For both (1) & (2), videotapes are post-analyzed with a
semi-automated image measurement system comprised of a computer-controlled
VCR, video capture card, and Optimus 6.5 image analysis package.
Next: Experimental studies of evolution in natural populations