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 to the most common groundfish species, polar cord. Because it is not a commercial species detailed information on the life history and ecology is lacking, and physical processes that influence the dynamics of this species are not well understood. Analyses of ichthyoplankton and bottom trawl surveys in the Barents Sea together with hydrographic information on water mass circulation and historical observations of spawning, bottom sediment classification and distribution of prey items provide the first comprehensive look at the life history and ecology of this 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 their distribution and are most abundant along the shelves and slopes of 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 area suggest that spawning of long rough dab takes place mainly in the western and central Barents Sea and along the northwest coast of Norway, corroborating Milinskyʹs hypothesis of an east to west spawning migration. A spawning migration in the direction opposite to larval drift would permit long rough dab to maintain its position within the region, a strategy common to many other demersal and pelagic fish in the Barents Sea. The distribution pattern of newly-settled and age-1 juvenile long rough dab is closely linked to the physical oceanographic processes of water masses, in particular the North Atlantic water mass, and the drift of early life-history stages in the system of currents along coastal areas and the Polar Front. The association of large aggregations of juveniles with sediments of a particular structure and a high biomass of benthos may be more than coincidental and would indicate that other physical factors may influence both settlement in the oceanic nursery areas and the overall pattern of distribution of the population.