A Surprise Occurrence in Acoustic Bottom Backscatter Measurements Conducted in the Eastern Bering Sea

• Main Authors: Huff, Lloyd C, Fonseca, Luciano E.
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2007
• Subjects: Oceanography and Atmospheric Sciences and Meteorology; Bering Sea; Fairweather
• Online Access: https://scholars.unh.edu/ccom/385; https://scholars.unh.edu/cgi/viewcontent.cgi?article=1384&context=ccom

Acoustic backscatter measurements at different frequencies were made in the eastern Bering Sea in August 2006 from the NOAA Ship Fairweather. The measurements consisted of approximately 2,250 nm of trackline acoustic backscatter data from a 100 kHz RESON model 8111; 2,250 nm of trackline acoustic backscatter data from a 40 kHz Reson model 8160; 750 nm of trackline acoustic backscatter data from a 455 kHz Klein model 5410; and 750 nm of trackline acoustic backscatter data from a 180 kHz pre-production Klein model 7180. The two Klein systems were each towed SW-NE once along the same specified 750 nm of tracklines. The two RESON systems were each operated twice SW-NE and once NE-SW along the same tracklines as the Klein systems. The acoustic backscatter was typically what might be expected from a flat, featureless expanse of fine grained sediments. However, there was a chance encounter with an embedded community of gastropods that was documented both with bottom grab samples and video footage of the seabed. The presence of the embedded community of gastropods drastically changed the level and angle dependence of the backscatter. This paper presents a comparative analysis of the backscatter properties of the gastropod community that were observed at 40 kHz, 100 kHz, 180 kHz and 455 kHz.