In recent years the red king crab has spread westwards to new areas off the coast of Finnmark and Troms counties and offshore in the Barents Sea. The Norwegian government has initiated a research programme to study its effect on the ecosystem. However, the knowledge about the impacts of the crab as an introduced species on the indigenous ecosystem is limited so far.
A western boundary to limit the spread
Until 2007 the management of king crab was based on an agreement between Russia and Norway. In order to limit the spread of king crab westwards, the two countries in 2004 agreed to establish a western border for the joint management of king crab at 26*E. The border was established to give Norway a free rein to pass the necessary and appropriate measure west of this boundary in order to limit the further spread of red king crab, until more knowledge about the ecological impact of this introduced species is obtained. Norway has maintained this border after the agreement on joint management with Russia came to an end in 2007.
The Norwegian management of king crab is today based on a White Paper adopted by the Norwegian Parliament in March 2008. In Norwegian waters east of 26°E and south of 71° 30' N the king crab fishery is regulated by quotas, and access is in general limited to vessels below 13 meter (overall length). The regulatory period in this fishery is from 1 of August to 31 of July, and for 2011/2012 the Norwegian TAC of king crab in this area is set at 1250 tons. The minimum legal size has this year been reduced from 137 to 132 mm carapace length.
The king crab fishery is regulated by quotas only in the eastern part of Finnmark- in the area adjacent to the Russian border. In addition to this, we have a free fishery of king crabs outside the regulated area.
Due to stock abundance, the commercial fishery for king crab is mainly conducted in coastal waters. The commercial quota has been distributed to about 500 vessels, with full quota to vessels where the owners are professional fisherman and half quota to vessels where the owners are part-time fishermen.
Stock size estimated annually
The Institute of Marine Research estimates the king crab stock size annually in the regulated area, and delivers quota assessments to the Directorate of Fisheries. The Directorate of Fisheries appraises the assessments and remits management advices to the Ministry of Fisheries and Coastal Affairs. Then the Ministry set the TAC, based on the scientific assessments and the management advices.
Recent investigations have revealed significant impact of the crab on soft bottom fauna. The areas of the Varangerfjord have been facing high concentrations of king crabs for several years, with a high number of species. The biomass of benthos is reduced. Large specimens of mussels, echinoderms and other species are almost absent. Currently, the fauna in these areas mostly consist of high numbers of small mussels, brittle stars and polycheates. In addition, the number of foraminiferas seems to have increased.
There are also indications of a change in the soft bottom sediment where all large specimens are removed, due to a reduced oxygenation downwards in the sediment. This may deteriorate mineralization processes in the benthic ecosystem. This will result in limited food availability for the king crab, and it would likely entail a reduction in the standing stock of king crab in Varangerfjorden in near future. It is also worth noting that the impact of the king crab is not necessarily always as dramatic as it appears on underwater pictures. In many cases, the sandy and empty-looking bottom sediment on which the king crab is photographed was the same before the king crab came to those areas.
For further information about effects of the king crab on the ecosystem, see: Oug, E., Cochrane, S.K.J., Sundet, J.H., Norling K. & Nilsson, H.C. 2010. Effects of the invasive red king crab (Paralithodescamtschaticus) on soft-bottom fauna in Varangerfjorden,northern Norway. Mar Biodiv. 41: 467-479. DOI 10.1007/s12526-010-0068-6