Recent Echo Sounder Studies
Abstract
HODGSON1 has shown that shoals of several species of fish give rise to traces on echo-sounders, and that a species may be identified by the shape of its trace. Echo-sounder records taken more recently by research vessels of this and other laboratories have shown that traces can be caused by an increasing variety of organisms covering a wide range of sizes, and that physical discontinuities in the water column are often associated with pronounced traces. For example, in August 1951 traces were obtained over a wide area off Whitby by the R.V. Platessa, using a Marconi sounder. They were found to be at a depth corresponding to that of a sharp thermocline, and small whiting about 3 in. in length, large medusæ, herring and Ammodytes larvæ were caught with a pelagic trawl at the depth of the trace. As the thermocline persisted outside the area in which the traces were recorded, the echo could not have been caused by the thermocline itself.
- Publication:
-
Nature
- Pub Date:
- July 1952
- DOI:
- 10.1038/170071b0
- Bibcode:
- 1952Natur.170...71T