Accession Number:

ADA030340

Title:

Acoustic Volume Scattering Measurements with Related Biological and Chemical Observations in the Northeastern Tropical Pacific.

Descriptive Note:

Research rept. Oct 73-Dec 75,

Corporate Author:

NAVAL UNDERSEA CENTER SAN DIEGO CALIF

Personal Author(s):

Report Date:

1976-07-01

Pagination or Media Count:

28.0

Abstract:

Measurements of acoustic volume scattering from 1 to 40 kilohertz were made in the Eastern Pacific Ocean with accompanying biological trawls and chemical determinations of several oceanographic parameters of the water column. This report summarizes results from one of the several stations occupied. Acoustic continuous-wave pulse measurements at 2.0, 3.5, 4.0, 4.3, and 12 kilohertz indicate that the daytime scattering is frequency dependent, originating from a layer whose average depth is 320 meters, and is caused primarily by midwater fishes containing swimbladders. Explosive source measurements of scattering from 1 to 20 kilohertz made during two migration periods descent followed by ascent indicate that the largest swimbladders, which contribute significantly to the low frequency scattering, migrate at constant mass in both directions. In addition, comparison of day and night acoustic observations with those obtained during migratory periods indicates that these same fishes secrete or resorb amounts of gas into or out of hte swimbladders, in an apparent attempt to control buoyancy. Author

Subject Categories:

  • Physical and Dynamic Oceanography
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE