AFSC/RACE/GAP/McConnaughey: QTC View Study- 1997- GIS

In early 1996, Quester Tangent Corporation (QTC) and the National Marine Fisheries Service (NMFS) Alaska Fisheries Science Center (in Seattle) formed a strategic alliance to apply QTC seabed classification technology to the problem of groundfish habitat descriptions. The Bering Sea supports about 300 fish species, many of which are demersal species. This stock supports sizeable fisheries, as indicated by landings at the Bering Sea port of Dutch Harbor in excess of 579 million pounds in 1996 and 678 million pounds in 1999 (the highest in the U.S.). By comparison, in 1981 the landing at Dutch Harbor was 73 million pounds. This rapid increase in catch highlights the need for effective management to ensure sustainability. After connecting the QTC VIEW full waveform acquisition system (ISAH-S) to the Simrad EK-500 scientific echosounder on the NOAA ship Miller Freeman, over 9,000 miles of track line data were collected in the eastern Bering Sea between June and August 1999. The raw data consist of digital echo traces of the full water column and seabed substrate. They were collected at two frequencies, 38 kHz and 120 kHz. Based on an average rate of one ping recorded per second, approximately four million individual echoes at each frequency were obtained.

The data within this raster set represent the results of processing channel 38_12, which incorporated the 38 kHz frequency data, using a reference depth of 90 meters and stacks of 50 echoes to create a single classified data point through the PCA analysis. A rasterized grid was created from each Q value and then grid stacked to allow RGB representation of each data point in continous Q- space as opposed to categorical class.

The data were processed with a view to identify the best processing scenario to deliver an optimal classification scheme for Bering Sea substrate, and embodying the results in an acquisition system for deployment on vessels of opportunity operating in the Bering Sea. The processing study developed far beyond the original concept, leading to significant advances in methods and processing of surveys for acoustic seabed classification. This work and the conclusions are presented in the report cited herein.

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