Observations on sound scattering layers in the upwelling off N.W.Africa and in the North Equatorial Current

Observations with a 38 kc echosounder during the NECTAR III expedition in March/April 1982 showed distinct differences in patterns and densities of the Sound Scattering Layers (SSL) between the upwelling area off N.W.Africa and the waters of the North Equatorial Current. The pattern of the SSL in th...

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Bibliographic Details
Published in:Journal of Plankton Research
Main Author: Schalk, P.H.
Format: Text
Language:English
Published: Oxford University Press 1988
Subjects:
Articles
North Atlantic
Online Access:http://plankt.oxfordjournals.org/cgi/content/short/10/1/89
https://doi.org/10.1093/plankt/10.1.89
Description
Summary:Observations with a 38 kc echosounder during the NECTAR III expedition in March/April 1982 showed distinct differences in patterns and densities of the Sound Scattering Layers (SSL) between the upwelling area off N.W.Africa and the waters of the North Equatorial Current. The pattern of the SSL in the North Equatorial Current resembled that of the tropical North Atlantic Ocean, while in the upwelling area a deviating pattern was found. These different patterns reflect different depth distributions found in both zooplankton and mesopelagic fish from RMT 1 + 8 catches. The densities of the SSL were higher in the upwelling area than in the Equatorial Current, showing similarities with zooplankton biomass and abundance of mesopelagic fish, in contrast with the abundance of echopatches, usually interpreted as fish shoals, which increased towards the west.

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