In recent years the red king crab has spread westwards to new areas off the coast of Finnmark and Troms counties and offshore in to the Barents Sea. Although the knowledge about the impacts of the crab as an introduced species on the indigenous ecosystem is limited so far, the Norwegian government has initiated a research programme to study its effect on the ecosystem.
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 last couple of years there have occasionally been presented assertions and speculations on TV and in the newspapers that the red king crab are eliminating all other marine life on the seabed in the Barents Sea and leaving an “underwater desert” in its wake. This has been supported by underwater pictures, which show areas of soft bottom sediment with almost no visible life except from large concentrations of king crabs.
The truth of underwater pictures
As to the underwater pictures, it must be pointed out that soft bottom sediment (in contrast to hard bottom) often appear to be areas with almost no visible life. This is due to the fact that most animals at this kind of substrate are buried in the sediment, not on the top of it. Therefore, this type of seabed may look as a desert for a non-skilled person. Also, it must be pointed out that the large concentrations of king crab that have been observed in the same areas are due to seasonal hatching/spawning/mating behaviour, and do not reflect a permanent situation during the whole year.
Furthermore, there is so far no evidence in scientific studies for such assertions and speculations. Indeed, preliminary investigations in an area in Norwegian waters where the king crab have been located for at least 20 years, show no significant effects on the fauna, neither on species abundance nor on species composition. At the same time, however, this is far from sufficient to declare that the king crab has no such negative effects at all. Therefore, Norwegian marine scientists are continuously conducting studies to reveal any such impacts on the bottom ecosystems in the king crab distribution area in Finnmark. Such studies are, however, complex and substantial results cannot be expected in short time.