Feeding conditions of north-east Arctic (Arcto-Norwegian) cod larvae compared to the Rothschild-Osborn theory on small-scale turbulence and plankton contact rates

Data on first feeding North-east arctic cod larvae in Lofoten, sampled during the period 1976 - 1984, are examined to verify the theory on the influence of microturbulence on the contact rate between predator and prey (Rothschild and Osborn, 1988). The number of prey per gut of the cod larvae are compared to the concentration of prey, Calanus finmarchicus nauplii, and to data on wind speed and static stability of the upper layer. The data indicate that the contact rate increases by 2. 8 when the average wind speed increases from 2 m s -1 to 6 m s -1 . Independent data on cod larval cruising speed, the velocity and concentration of prey organisms, inserted into the model of Rothschild and Osborn (1988) show a comparable increase of the contact rate of 2.2 for the same increase of wind speed. Larval stages of North-east arctic cod are important for the formation of the year class. Larval stages are confined to the mixed layer, and therefore the variable contact rate induced by wind mixing is an important regulatory mechanism for the formation of year class strength

Investigations in Vestfjorden 1978. 1.Fresh water budget and wind conditions

Mean monthly values of freshwater run off to the different parts of Vestfjorden has been computed. About 90 per cent of the run off comes from the eastern side of the fjord. There is a pronounced yearly amplitude of the run off with a maximum during summer and a minimum during late winter. Due to evaporation from the sea surface the net flux of fresh water into Vestfjorden is very small in winter, some times it even is negative. Wind conditions during winter is mainly dominated by two kinds of events: drainage of cold air from the mountains with easterly and northeasterly winds, and cyclone passage with southwesterly winds. The topography of the mountains surrounding the fjord is largely influencing the wind conditions. The wind conditions during April 1978 are described particularly