Larval and small juvenile cod Gadus morhua concentrated in the highly productive areas of a shelf break front

The early llfe of cod was studied dunng a survey programme covenng the northeastern North Sea, the Skagerrak and the Kattegat In May 1992 Our aim was to asses the interrelated effects of physical and biolog~cal factors on d~stnbutlon, growth and surv~val of larval cod In the present paper we descnbe the ~d e n t ~f i e d nursery areas of larvae/juveniles and analyse the connect~on between the distribution of cod and hydrograph~cal (frontal) charactenstics of the areas A total area of 67000 km2 was covered by statlons in a 10 X 10 nautlcal mile grid Sahn~ty, temperature, N 0 3 + N 0 2 and chlorophyll concentrat~on were proflled through the water column Zooplankton were sampled by a sub-mers~ble pump and abundance of fish larvae/juveniles were estlrnated by depth-integrating tows of a 2 m nng net The hydrographlcal measurements indicated a shelf break front posit~oned along the shelf slope In the southern part of the lnvestigatlon area, and w i t h ~n the zone of the front we observed enhanced prunary product~on and abundance of both phyto-and zooplankton The distnbut~on of larval and juvenlle cod was also related to the hydrography, the abundance of cod peaked wlthln a restricted zone and the aggregat~ons extended as a cont~nuous band along the front We suggest that the observed concurrence between a hydrograph~c front and cod larvae/juvenlles is a general and recurrent phenomenon based on the spawning h a b ~t s of cod and aggregation due to flow convergence at the front KEY WORDS. Gadus