Spatial and trophic ecology of fishes from boreal and arctic sectors of the Barents sea as inferred from stable isotope analysis.

Supervisor: Clive Trueman(University of Southampton)
Arctic marine ecosystems are warming faster compared to the global average. Recent studies show that increased temperature and salinity lead to a large-scale sea-ice retraction in the Arctic associated regions. Understanding species’ responses to environmental fluctuations as a result of climate warming is important for the sustainable management of resources. Large predatory fishes such as cod and haddock in the Boreal region of the Barents Sea are migrating poleward due to the increase in ocean temperature, and reduced sea-ice coverage which has been predicted to cause dramatic changes in the Arctic food web structure. The present study tests whether haddock and cod occupy similar trophic niches in the newly invaded Arctic region compared to their well-characterized niches in the temperate ecosystems using stable isotope analysis. The isotopic niche areas were calculated to define and compare the trophic structure of selected species between the different areas. Haddock occupy different trophic positions in the Barents Sea, and the North Sea. The juvenile haddock (and cod) have narrow isotopic niche width, and less likely to disrupt the Arctic food web structure. The adult haddock occupies a greater isotopic niche width than adult cod implying the potential of adult haddock to connect the Arctic modular food webs and reduce opportunities for the specialist taxa. However, the abundance of adult haddock is less than that of the adult cod, making the adult cod the main agent of modularization in the Arctic Barents Sea ecosystem.