Sonic Scattering by Biological Entities in the Coastal Waters off Mission Beach, California.
Abstract
An upward directed echo sounder was placed on the ocean floor off Mission Beach, California to determine the nature of sound scattering in the vertical column of water. Scattering density showed a pronounced increase in nighttime periods, with the scattering bodies exhibiting (1) unusual characteristics of movement, and (2) reactions to temperature and light stimuli. The scatterers, determined to be of a biological nature, appeared each evening with unfailing regularity in an unusually short period of time, and remained throughout the night until early dawn. In addition to the acoustic data, records of vertical temperature structure and visual and filmed observations were obtained, showing the possibility that the night interference effect, as it has become known, could be caused by swarms of shrimp-like mysids. Schools of fishes of several different varieties were also observed in the water and simultaneously recorded by the echo ranger.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 24, 1960
- Accession Number
- ADA048854
Entities
People
- John W. Donaldson
Organizations
- Navy Electronics Laboratory