Accession Number : AD0707085

Title :   BIO-ACOUSTIC AND BIOLOGICAL SAMPLING GEAR STUDIES.

Descriptive Note : Final rept. 1 Jan 68-31 Mar 70,

Corporate Author : SMITHSONIAN INSTITUTION WASHINGTON D C

Personal Author(s) : Aron,William I. ; Jossi,Jack W. ; Pieper,Richard E.

Report Date : 31 MAR 1970

Pagination or Media Count : 88

Abstract : On a portion of the round-the-world voyage of the USC and GS ship OCEANOGRAPHER, the Smithsonian Institution made plankton collections with an International Cooperative Investigations of the Tropical Atlantic (ICITA) net and an Indian Ocean Standard Net (IOSN), and at the same time collected acoustical data. A comparison of the bridled ICITA net with the unbridled net showed that the mean ratios of the catches examined were not significantly different from 1.0; i.e., the hypothesis that the catches of the two nets are equal is not proven false. The mean ratios of the displacement volume of organisms collected are significantly different between day-time tows and night-time tows. A comparison of the bridled ICITA net with the unbridled Indian Ocean Standard Net showed that the ICITA net caught a significantly greater number of organisms than the IOSN. This difference was more pronounced during the night than during the day. Near-surface scattering was recorded at all day-time stations where biological sampling was carried out. Adult euphausiids were caught in greater numbers in the surface waters at night than during the day. This does show vertical migration but does not necessarily indicate a correlation with migrations of deep scattering layers to the surface at night. It is suggested that euphausiids are not the scatterers of sound at the frequencies used by the echo-sounders. (Author)

Descriptors :   (*MARINE BIOLOGY, ACOUSTICS), UNDERWATER SOUND, PLANKTON, AQUATIC ANIMALS, COLLECTING METHODS, ECHO RANGING

Subject Categories : Biological Oceanography
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE