BIO-ACOUSTIC AND BIOLOGICAL SAMPLING GEAR STUDIES.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 31, 1970
- Accession Number
- AD0707085
Entities
People
- Jack W. Jossi
- Richard E. Pieper
- William I. Aron
Organizations
- Smithsonian Institution