Pelagic cod and haddock juveniles on the Faroe Plateau: Distribution, diets and feeding habitats, 1994-1996

Inside the tidal front that separates the Faroe shelf water from the oceanic environment, the zooplankton was dominated by neritic copepod species, mainly Acartia longiremis and Temora longicornis, but with a variable mixture of the copepod Calanus finmarchicus. The zooplankton biomass in this water was
low in 1994 and 1995, but was markedly higher in 1996, due to increased abundances of C. finmarchicus. Outside the tidal front, the zooplankton was dominated by C. finmarchicus and the biomass was higher than in the shelf water. The abundances of juvenile cod and haddock did not fit positively with the abundances of food during these years. The mean length of the juveniles of both species was smaller in the year with the highest zooplankton biomass in the shelf water (1996) than when the biomass was lower (1994 and 1995). The juveniles were generally more concentrated in the shallow area when the food was abundant in those areas than when it was sparse. Their stomach contents were partly reflected by the in situ zooplankton composition and their size. At between 15 and 35 mm in length, both species in the shelf water preyed mainly on the copepods T. longicornis and C. finmarchicus, while those outside the tidal front fed on C. finmarchicus. At about 35–40 mm in length, prey in the subclass Malacostraca and fish larvae were added to the diet. However, the haddock
juveniles were clearly smaller than the cod juveniles when they switched over to malacostracans. There was an overlap in feeding habitats as well as niches in similar sized individuals of the two species.