Distributions of Target Strengths and Horizontal Dimensions for Aggregations and Schools of Marine Organisms.

摘要

Recordings of absolute echo levels from marine acoustic targets (schools of pelagic organisms) were analyzed to measure distributions of peak target strengths at two frequencies, 11kHz and 30kHz. Since the recordings were not simultaneous,different sets of targets were analyzed at each frequency. At 30kHz,peak target strengths ranged between - 10dB and 28dB with a mean target strength of 18.8dB. At 11kHz,the measurements ranged from -25dB to 11dB with a mean of 4.2dB. Distributions of two target horizontal dimensions were also obtained. These dimensions ranged between 5meters and approximately 400meters with a mean of approximately 40meters. Most probable target diameter (highest frequency of occurrence) was approximately 20meters. A trend toward higher target strengths for larger targets was observed at both frequencies. (Author)