Feeding conditions of north-east Arctic (Arcto-Norwegian) cod larvae compared to the Rothschild-Osborn theory on small-scale turbulence and plankton contact rates
Original version
This report is not to be cited without prior reference to the authorsAbstract
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.