The Norwegian Sea and Icelandic Waters ecoregions are the latest additions to ICES ecosystem overviews. The overviews are a step towards a more integrated approach to management of ocean resources, providing a description of the ecosystems, identifying the main human pressures, and explaining how these affect key ecosystem components. These two overviews have now been published in an interactive diagram format.
Fishing pressure
"The Icelandic Waters overview demonstrates that the most significant use of the marine ecosystem is through fisheries. This is not surprising given the importance of fisheries in Iceland," explained Gudmundur Thordarson, the Icelandic member of the ICES Advisory Committee (ACOM).
"It is interesting that as management of fishing effort has increased in Icelandic waters as a result of harvest control rules for the main fish stocks, human pressures on the ecosystem have decreased. This does not only affect fishing mortality and stock biomass in the target species but also other stocks caught in mixed fisheries. But what is really interesting is to see the decrease in effort in terms of amount of fishing operations (such as hours trawled, number of hooks or fishing effort) and subsequent decrease in potential seabed abrasion."
The overview also highlights various factors that are of concern in the country's fisheries, such as bycatch of marine mammals, seabirds and non-target species.
"We observe quite significant changes in the ecosystem such as changed distribution of baleen whales and capelin and increased biomass of mackerel. These are all discussed in the overview."
Seabird populations declining
The Norwegian Sea is large (1.1 million km2) and deep (up to 4 km) and is characterized by relatively warm saline Atlantic waters in the eastern parts and cold, fresh polar waters in the west. Fisheries is also the main pressure in this ecosystem.
"Due to the sea's great depths, the main fisheries are pelagic, but fisheries for demersal species take place along the continental shelves. The main pelagic fish species are mackerel, herring, and blue whiting. The herring stock has been suffering from low recruitment in the recent decade and is relatively small compared to its potential, while the other stocks are large and support large catches. The mackerel stock has expanded in recent years, probably as a combined effect of increased stock size and increased water temperatures," explained Norwegian ACOM member Harald Gjøsæter.
While the fish stocks are mostly doing well, seabirds have shown a decrease in the region over the last three to five decades.
"It is not clear which factors are causing this decline, but unsuccessful breeding for several seabird species and likely drastic changes in the availability of fish in their first year of life (especially herring) could be two of them. It could also be linked to variation in ocean climate," said Gjøsæter.
"The Norwegian Sea remains relatively clean with low pollution levels compared to marine areas in many industrialized parts of the world. Fisheries are the main human pressure in the ecosystem but human activities also involves transportation of goods, oil, gas, and tourism, with contaminants coming from outside the boundaries of the ecoregion."
