For over 20 years, efforts have been made to restore the cod stock in the Porsangerfjord in Finnmark to its former heights. As in many other fjords, overfishing and sea urchin invasion have led to coastal cod being critically endangered and red-listed. – Although there are both crabs and other species in the Porsangerfjord, there has always been a strong desire to bring back the cod stock in the inner parts of the fjord, says researcher Hans Kristian Strand at the Institute of Marine Research. And now, after many years of research, Strand and his colleagues are finally on the track of a solution. At the very center stands a man-made kelp tree. A kelp tree is shaped like a tall fir tree. The kelp grows on the structure, and not on the seabed. At the Institute of Marine Research’s field station at the Porsangerfjord, they have been researching coastal cod for over 20 years. Photo: Beate Hoddevik Wants to build a park of artificial forest For a long time, much of the kelp forest was gone in the Porsangerfjord. It had been eaten by large numbers of sea urchins. It is serious because the ocean’s forest is both a food dish and a hiding place for cod fry and other marine animals. When the king crab eventually established itself in the Porsangerfjord, the kelp forest returned. However, the population of coastal cod has not increased. Now the researchers will try to give the cod in the Porsangerfjord a new start. Hans Kristian Strand explains that coastal cod is like salmon. It has ownership of the fjord, in the same way as the salmon has ownership of its river. When it is about to spawn, after grazing on the resources out in the fjord, it will return to its old home. – But when the population is gone, no fry feel that the old spawning ground is their home. Then there are no coastal cod that return to the spawning ground either, says Strand. The researchers find a lot of fish fry in the kelp parks they have set up. Video: Institute of Marine Research The researchers will therefore release fry from the local coastal cod in artificial kelp farms. These must be placed in former spawning areas. It will start the production of eggs and juvenile fish. – We envision building kelp parks consisting of a thousand artificial kelp trees. We believe that these parks will give the small cod more protection than if it has to live in the kelp forest down on the bottom, where it has many enemies. Strand explains that the cod eventually head out into the fjord systems to find more food. – But when the spawning season approaches, we believe that the coastal cod will return to the safe spawning ground where it grew up. – It is the old hiking route that we hope to bring back to life, through this project, says Hans Kristian Strand. This film about the postponement of kelp forests was made by the Institute of Marine Research. Can save coastal cod An artificial kelp tree consists of a heavy plastic ring made of cotton. Long ropes are attached to the plastic ring, which are collected in a bladder or balloon at the top. Hans Kristian Strand explains that kelp spores in the water mean that kelp will eventually grow on the ropes in the kelp tree. – The grant reform of the construction, narrow at the top and wide at the bottom, means that the light reaches far down into the water column. It provides good growth conditions for the kelp. The researcher says they have been testing the kelp trees for several years, and the results so far are good. Work is now underway to establish a kelp park in a side fjord to the Porsangerfjord. If these kelp trees can help bring the cod population up in the Porsangerfjord, there will be hope for coastal cod in other fjords as well. – We believe that if we are successful in Porsangerfjorden, then with local adaptations we will be able to do the same elsewhere. Dagny Larsen shows a cod of 23.6 kg that was caught in the autumn at the end of the 1970s in the inner western parts of the Porsangerfjord. Now there are only small fish left. Photo: private Considered in several fjords In recent decades, hordes of voracious sea urchins have eaten up miles upon miles of kelp forest and turned the seabed along the coast into a desert. One of these desert areas is outside Melkøya in Hammerfest municipality. Now the researchers believe that the new kelp trees can also bring the kelp forest back here. And in the new year, kelp trees will be planted outside Melkøya. Tom Eirik Ness, nature and environmental advisor in Hammerfest municipality, says they have made several attempts to get the kelp forest back into their waters, but until now it has been impossible to stop the sea urchins. Now the new kelp trees have created new hope. The reason is that the kelp does not grow on the seabed, but on the ropes in the construction. – A sea urchin does not swim through water. It must have a firm bottom to be able to climb. So we have great faith that the sea urchin will not be able to conquer these reefs, and that the kelp forest will thus be left in peace. – If this is a successful patent, it will be a revolutionary way to speed up the kelp forest again, says Tom Eirik Ness. The tares forest project is a collaboration between the Institute of Marine Research, Porsanger municipality and Equinor and Hammerfest municipality. If the researchers are successful, the artificial kelp trees can save both the kelp forest and the red-listed coastal cod in Norwegian fjords. – We see that kelp is growing well on the trees we have set out in the Porsangerfjord, and we see that they attract fish fry. – What would have been fantastic was if we could establish a kelp forest in the middle of a grazed sea urchin desert, without them having had the opportunity to graze it again.
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Artificial kelp forest will try to save red-listed coastal cod – news Troms and Finnmark
