LIFE-HISTORY AND ECOLOGY OF LONG ROUGH DAB HIPPOGLOSSOIDES-PLATESSOIDES (F) IN THE BARENTS SEA

Long rough dab in the Barents Sea are numerically fifth in abundance t o the most common groundfish species, polar cod. Because it is not a c ommercial species detailed information on the life history and ecology is lacking, and physical processes that influence the dynamics of thi s species are not well understood. Analyses of ichthyoplankton and bot tom trawl surveys in the Barents Sea together with hydrographic inform ation on water mass circulation and historical observations of spawnin g, bottom sediment classification and distribution of prey items provi de the first comprehensive look at the life history and ecology of thi s species. Long rough dab are distributed from the coastal waters off western and northern Svalbard, south along the continental shelf edge to the northwest coast of Norway and eastward into the Barents Sea to Goose Bank. The greatest concentrations are located within the Barents Sea. Both juvenile and adult long rough dab overlap considerably in t heir distribution and are most abundant along the shelves and slopes o f various banks close to the Polar Front, in particular the slopes of Spitsbergen Bank. Analyses of icthyoplankton and demersal survey data together with historical data and hydrography of water masses in the a rea suggest that spawning of long rough dab takes place mainly in the western and central Barents Sea and along the northwest coast of Norwa y, corroborating Milinsky's hypothesis of an east to west spawning mig ration. A spawning migration in the direction opposite to larval drift would permit long rough dab to maintain its position within the regio n, a strategy common to many other demersal and pelagic fish in the Ba rents Sea. The distributional pattern of newly-settled and age-1 juven ile long rough dab is closely linked to the physical oceanographic pro cesses of water masses, in particular the North Atlantic water mass, a nd the drift of early life-history stages in the system of currents al ong coastal areas and the Polar Front. The association of large aggreg ations of juveniles with sediments of a particular structure and a hig h biomass of benthos may be more than coincidental and would indicate that other physical factors may influence both settlement in the ocean ic nursery areas and the overall pattern of distribution of the popula tion.