The Norwegian Sea is an area covering approximately 1.1 million km. The area covers two separate deep water basins with a water depth of 3000-4000 m, the Norwegian and Lofoten basins. Also, the shallower water is dominated by the Norwegian Atlantic tidal stream of the Gulf Stream. As a result of this constant flow of warm water, the area is largely free of sea ice, although it is mostly in the Arctic. And in zooplankton, Calanus finmarchicus prevails, which supports large pelagic stocks.
Unlike most of the other systems described, it is in the gap between the 200 nm zones extending eastward from Jan Mayen and westward from the Norwegian coast. And outside of the national territorial waters, there is a rather large area called the banana hole. Fishing in the Norwegian Sea primarily targets large and widely spaced pelagic stocks, and these are as follows.
• Norwegian spring-laying herring,
• Blue whiting,
Limited amount of horse mackerel,
The area also has a high squid biomass. There are several abundant pelagic stocks covering both the Norwegian and Barents Seas. Especially the Norwegian spring spawning herring was caught in both the Norwegian and Barents Seas, which used the Barents Sea as a nursery ground before moving to the Norwegian Sea at the age of 3 or 4.
The mackerel and blue whiting in the Norwegian Sea represent the northern tip of the stocks extending to the Iberian peninsula. Thus, there are important links between the Norwegian Sea and neighboring ecosystems, and as a result, most stock assessments are conducted on a larger scale than the Norwegian Sea alone. Deep water benthos dominate the seabed of the main basins. A number of cold-water coral reefs are found along the continental shelf closer to the Norwegian coast. These corals are slow-growing and support a high biodiversity, receiving protection in the form of exclusion zones for bottom trawls.
The mink whale population defined in the Barents Sea section passes through the Norwegian Sea on their migration route. And while some of the stock remains in the Norwegian Sea for summer feeding, the rest will likely encounter herring en route. Other major marine mammals in the area include predators, larger whales such as humpback whales, blue whales, and finned whales. In addition to these, there are also white-billed and white-sided dolphins and various dolphin species. In addition to the top-down forcing exerted by marine mammal predators, there is considerable bottom-up forcing from the large number of large pelagic stocks that feed largely from the same source of plankton. Recently, large biomasses of mackerel and blue whiting are associated with the decrease in zooplankton biomass.
Major fisheries target the broad pelagic zone and therefore the assessment and management of these species is carried out through an international ICES WG on the widely dispersed species, WGWIDE. Stretching beyond the Norwegian Sea, 7 countries reported catching over 9000 tons of mackerel in 2014. These Faroes reported catches of over 75,000 tonnes, all in Greenland, Iceland, Ireland, Norway, Russia and the United Kingdom. Over 9000 tons of NSS herring out of a total of 460,000 tons and 11 countries reported more than 9000 tons of blue haddock. Although shears are believed to exist, they are highly variable, with 0% or 100% discards when the entire carriage is discarded. As a result, compiling estimates of discards are difficult and deemed unsatisfactory by WG. However, it is believed to be low for blue whiting. Both mackerel and blue whiting are evaluated with the SAM age catch model. Norwegian spring-laying herring was evaluated with a VPA model. However, at the time of writing, an ongoing benchmarking process reviews the selection of the evaluation model. The mackerel stock extends from the Iberian coast to the northern Norwegian Sea and supports a very valuable fishery. Although there is angling in the south, Norwegian Sea fishing relies on freezing trawlers, pelagic trawlers and purse seiners. The assessment is based on age-catch data and a recruitment index from IBTS surveys in the North Sea. We also look at the Norwegian Sea ecosystem survey (IESSNS) and an RCC index from the egg survey and tag recapture data. In stock valuation, there is a significant uncertainty with the perception of stocks changing between assessments.
In the absence of an agreed management plan, the ICES makes recommendations on the basis of the MSY after the mackerel stock has spread to Icelandic and Faroese waters. Blue whiting stock is also found in a wide range in the East Atlantic and is believed to be the main nursery area of the Norwegian Sea. The evaluation showed a significant downward revision in 2015 due to the decrease in the survey index. The assessment is considered to have high but not measurable uncertainties. The stock is managed by an ICES approved precautionary HCR agreed between the EU, Norway, Faro and Iceland. And in 2014 hunting was slightly below recommended quotas. Although demersal trawlers also target blue whiting in the Norwegian Sea, much of the catch comes from large pelagic trawls, with 92% of catch caught in the first half of the year. The Norwegian Sea forms the main nursery ground for stock, but most of those caught occur further south.
Unlike other major pelagic stocks, NSS herring is largely confined to the Norwegian Sea and neighboring Icelandic and Faroese waters, except for the nursery area in the Barents Sea (not subject to commercial fishing). The management of fisheries is therefore controlled by Norway and Russia, and a long-term management plan has been in place since 1999. The plan was evaluated by ICES and found for precautionary purposes. The Norwegian spring-laying herring was pulled off the coast of Norway in the late 1960s, after falling to 0.1% of its previous SSB.
However, an exceptionally large year class in 1983 led to the recovery of the animals and the maintenance of spawning grounds near the Norwegian coast and a widely dispersed habit of feeding along the northern Norwegian Sea. A number of poor year classes caused a drop in stock, with the 2015 assessment predicted to stabilize above Blim, to the extent that the stock was estimated to be below Bpa of 5 million tons.
While the Norwegian fleet is dominated by purse seiners (92%) and pelagic trawlers (8%), the Russian fleet also has a variety of trawlers. In the Norwegian Sea, administered by Norway, the minimum catch size of 25 cm limits fishing from targeting largely adult individuals. DisclosedIn addition to fishing, a small development catch is available for Calanus finmarchicus. Calanus is suppressed to extract the oil marketed as an omega-3 supplement. This highlights that as a low trophic species, it is unlikely to contain accumulated contaminants in the oil. The remaining mass is sold as fish meal. Although fishing is currently profitable on a small scale and harvesting 1% of the stock can produce more than 2 million tons of marine oil and protein, it is unclear whether fishing will be commercially viable when it expands. It is also beyond a relatively small market for omega-3 supplements.
Author: Ozlem Guvenc Agaoglu