Distribution and standing stock of zooplankton sound-scattering layers along the north Norwegian coast in February—March, 1978

The presence or absence of sound-scattering layers from Skjerstadfjorden to Lyngen-fjorden was registered with the aid of an EK 120A echo-sounder. A Tucker trawl and a pelagic capelin trawl were used to sample in and out of the registered sound-scattering layers (SSLs). Salinity, temperature, density, specific volume anomaly, light, and chlorophyll a were measured at each station. The SSLs were composed mainly of krill. The formation of SSLs did not seem to be associated with hydro-graphic factors, nor with chlorophyll a concentration. SSLs did seem to require a depth of at least 100 m. Diurnal vertical migration was related only to changes in light intensity.