Meganyctiphanes norvegica(Crustacea: Euphausiacea) In the Kattegat: Studies on the horizontal distribution in relation to hydrography and zooplankton

Abstract

Adult Meganyctiphanes norvegica and two smaller euphausiid species Thysanoessa raschii and T. inermis were found in the Kattegat exclusively at one location, the Laso-Deep, In contrast, larval euphausiids were encountered at almost all stations on a section from the Kattegat into the Skagerrak conducted during August 1983. How adults were eliminated from the Kattegat was not clear, although currents and migration must have played a role influencing the distribution of both larvae and adults. Low salinity in the Kattegat was not a limiting factor of existence. Euphausiids presumably concentrated at the Läsö-Deep by swimming actively in search of high density seawater, but local currents also seemed to playa role. M. norvegica finds favourable nutritional and hydrographic conditions there, reproduces successfully and achieved a greater body size than another population in the Skagerrak compared during the summer survey. In August, euphausiid larvae constituted up to 51% of the standing stock (dry weight) of zooplankton in the Kattegat and up to 57% in the Skagerrak and therefore were important members of the zooplankton community.