This portal tracks the research and sea-going activities of the Fisheries Engineering and Acoustic Technologies (FEAT) Team from NOAA¿s Northwest Fisheries Science Center. Follow us as we use acoustics, trawling, and oceanographic sampling to learn about the Northeast Pacific Ocean.
Today we calibrated our acoustic echosounders in beautiful Monterey Bay, CA. Compared to our previous attempt, which involved 30 knot winds and 10’ combined seas (5’ swell + 5’ wind waves), conditions today were perfect. Winds <3 knots, 1’ seas, sunshine, and 200+ common dolphins (Delphinus delphis) that swam around us feeding on a large school of fish that passed under us. Perfect!
A precision-machined 38.1 mm tungsten carbide sphere, which reflects a known amount of acoustic energy, is used to calibrate the echosounders. Three downriggers—two on the starboard side and one on the port side—are mounted onto the Shimada’s railing. Each downrigger lets out a very thin line, and the three lines are attached together at a swivel below the Shimada. The sphere is then suspended below the swivel, and—with skill and some good luck—below the echosounders as well. We can control the location of the sphere in the acoustic beam by having Chu’s computer program instruct each downrigger to let out, or take in, line.
After the sphere has been moved around the acoustic beam, we analyze the data to see if we have to adjust settings based on the calibration results. Calibrations of the Shimada echosounders are done several times a year to ensure that systems are running correctly and that we have high quality data for our analyses. Today’s calibration was the first of the year for the Shimada and it was a success. Mission accomplished.
Tagged: Winter hake survey