Title







 


 

Rapid characterization/mapping of
shelf seabed habitats and measuring the dynamics of large sessile seabed fauna
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 habitat patterns.

For (2), other devices such as ROVs, SSBA (where shallow) may be used to deploy
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
of guppies