OCEAN ACRE: AN INTERIM REPORT.
Abstract
Seven cruises were made between October 1967 and September 1969. A 6-foot IKMT was used on two cruises, a 10-foot IKMT was used on five. In addition, trials with large Engel trawls were carried out on one cruise. A discrete-depth sampler was employed with the 6-foot IKMT on one cruise and with the 10-foot IKMT on two cruises. Of 277 samples, 153 are from discrete-depths. Discrete-depth coverage is good for depths of 50-550 m both day and night, but sparse from 600-1300 m. Non-discrete samples have been made as deep as 2500 m. The most abundant fishes are species of the families Myctophidae, Gonostomatidae, Sternoptychidae, and Melamphaidae. At least two abundant species with well-developed swimbladders do not migrate and are correlated with a permanent 400-600 m scattering layer. Other species occupy this stratum during the day, but migrate upward at night, at which time the density of the scattering layer is diminished. Many migrators apparently inhabit deep thermocline depths of 700-1100 m during the day and migrate upward at night, although a few species remain at these depths at all times. Most migrators regardless of daytime depths, occur in the upper 250 m at night. Complicated patterns of scattering layers at night may be attributable to the different individual migratory habits. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1970
- Accession Number
- AD0703672
Entities
People
- Clyde F. E. Roper
- Robert H. Gibbs Jr.
- William Aron
Organizations
- Smithsonian Institution