Accession Number:

ADA028930

Title:

Fish School Target Strength and Doppler Measurements

Descriptive Note:

Research and development rept. Nov 1974-Mar 1976

Corporate Author:

NAVAL UNDERSEA CENTER SAN DIEGO CA

Report Date:

1976-07-01

Pagination or Media Count:

36.0

Abstract:

A study of the acoustic characteristics of fish schools necessary to establish engineering parameters for the design of acoustic systems for the Navy was undertaken. Target strengths of 10,534 fish schools in the California Current System CCS were measured. For pulse durations of 10 milliseconds, the average target strength was -7.3 decibels with a standard deviation of 5.3 and the average target strength for intensity was -2.4 decibels. Of all schools 73 had target strengths greater than or equal to -10 decibels no values greater than 20 decibels were measured. Peak target strength was found to be both pulse length and range dependent. Although the Doppler data were considered to be preliminary, 32 of the 260 schools examined displayed speeds greater than or equal to 1 knot. No ship avoidance by the schools was observed, and no speeds greater than 5 knots were recorded. Schools size varied in extent from 5 to 250 meters, measured acoustically along the axis of the sound cone. The mean target extent was 64 meters with a standard deviation of 42 meters a strong mode existed at 35 meters.

Subject Categories:

  • Acoustic Detection and Detectors

Distribution Statement:

APPROVED FOR PUBLIC RELEASE