By Beate Hoddevik Sunnset
Last week, the data from all of the listening buoys was extracted for analysis. The buoys were also used to collect data last year, and preliminary results show that temperature plays less of a role in the seasonal migrations of king crabs in Porsangerfjorden than in their native areas.
- In the native areas of the king crab, temperature governs migration between deep and shallow water. In Norway the king crab is an introduced species, and it has yet to fully adapt to the local environmental conditions, explains scientist Jan H. Sundet.
The aim of the project is to find out how long king crabs remain at various depths at different times of year. This will enable us to assess the impact of the king crab on flora and fauna in the areas where it has established itself. So far, results show great individual variation in both behaviour and the distance travelled by the crabs, but in general it is true to say that they are constantly moving, seeking out good areas in terms of access to food and reproductive considerations.
Lose their tags
One of the challenges when tagging crustaceans, such as king crabs, is that they change they shield their outer skeleton in order to grow. The acoustic transmitters are attached to the shell, and therefore becomes useless if the crab moult during the project.
- Large king crabs moult less frequently than small crabs, and in general change their shells with interval of a few years. That’s why we’ve tried to only tag large individuals, so as to receive signals from the transmitters for as long as possible, explains Sundet. Only one similar tagging experiment has been performed with king crabs, in Alaska.