Various types of jellyfish have been raising concerns along the coast of Norway, after some left large swatches of red slime in the far north and others, farther south, threaten cod stocks. Researchers are following the situation closely.
The so-called kronemanet, for example, has invaded several fjords from the Sognefjord in the south to Nordland in the north. Researchers at the Norwegian University of Science and Technology (NTNU) in Trondheim told state broadcaster NRK that they can live to be 30 years old, weigh four to five kilos, thrive in deep water and eat both cod eggs and the same food as the codfish themselves.
While they could report this week that the numbers of this troublesome jellyfish have declined, fishing crews off the coast of Nord-Troms and Finnmark were reporting a so-called “red slime” at sea and in their nets that’s tied to another type of jellyfish known as ribbemaneter. Jan Helge Fosså of the ocean research institute Havforskningsinstituttet told NRK the slime was caused by a “blossoming” of the jellyfish as they die out, normally in the late autumn and winter.
“Many of them are currently wasting away on the sea floor, leaving the red-coloured slime that gets caught in fishing gear as it coagulates. Fosså called the phenomenon “completely natural,” even though it’s often not spotted as it has been this autumn off the coasts of Lyngen and Kvænangen in the far north.