Towed Video - Benthic survey of Douglas Shoal (17-Apr-2010 - 18-Apr-2010 )

Brief description

This data consists of 5097 records derived from 8 tows covering 16.692 km at 3.27m resolution, over a depth range of 7.7 to 22.0 meters. Classification of the benthos and substrate was based on 17 benthic classes and 6 substrate classes.

Summary of the primary benthic categories recorded
Macroalgae and Filter feeders 32.29%
Hard Coral 7.10%
Macroalgae 50.95%
NoBenthos 9.65%

Summary of substrates recorded
Rubble 1.39%
Grounding 8.10%
Sand 5.47%
Limestone 85.03%
A custom interface has been developed by AIMS staff for reading Towed Video tapes.

Lineage

Maintenance and Update Frequency: asNeeded

Statement: Statement: Sea surface conditions and strong currents due to spring tides, made it difficult to maintain a Towvid course in the prevailing sea conditions and resulted in a meandering track intersecting the known positions of the Shen Neng 1.The visual imagery of the benthic habitat was captured using a 1/3 inch single CCD colour video camera mounted on a tow frame and controlled by a winch with 320 m of electromechanical cable. The video signal was recorded on a shipboard miniDV tape recorder. In addition to the visual imagery, the miniDV tape recorder received GPS and sounder data (latitude and longitude, ground speed, true heading, date, depth and time), which was recorded on the audio track. The computer-based application developed by AIMS for the analysis of tapes is described in:Speare PJ, Johansson C, Depczynski M, Meekan MG (2008) Marine habitats of Southern Melville Bay using towed video and aerial photography. Final Report to Charles Darwin University/Alcan Gove Pty Ltd. Australian Institute of Marine Science. 25 p.Substrate and benthic categories employed for towed video to classify the habitats and individual organisms recognised:Substrate Class (abiotic substrate components):GroundingLimestoneRubble (5-50mm)SandBenthos Class (overlying benthic organisms):Hard Coral, MediumHard Coral, SparseMacroalgae and Heterotrophs, MediumMacroalgae and Heterotrophs, SparseMacroalgae, DenseMacroalgae, MediumMacroalgae, SparseNo BenthosIndividual Organisms:Solitary CoralSea PenWreckageNoneThe percentage cover of benthic communities was classified as follows:S - sparse (0 - 30% cover)M - medium (30 - 60%)D - dense (>60%)