Diving is currently the most common method in Norway for harvesting sea urchins. In the future, the divers may be replaced by a remotely-operated underwater vehicle (ROV). There is an extremely high demand for sea urchin roe, which is one of the world's highest paid seafood products. Wild sea urchins are today harvested in the sea by divers and undergo raw enhancement before they are sold.
Trials using the ROV Seabed Harvester show that this can be a new method for harvesting sea urchins.
The ROV, which is designed and built in Norway, is a prototype built for harvesting sea urchins and other bottom-dwelling species such as scallops and cockles.
Nofima, in collaboration with a sea urchin producer, has carried out a full-scale trial of the ROV in an area that is used for commercial harvesting of sea urchins.
Two divers participated in the trials in order to see how effective the ROV actually is. They dived for sea urchins while the ROV was in action. Afterwards, the scientists compared the result.
During the first tests, the divers harvested far more sea urchins than the ROV. This evened out somewhat after a while, but the divers were still the most effective. During one test, the ROV harvested nearly 300 kg of sea urchins in one hour.
"The trials show that the ROV has huge potential," says Senior Scientist Sten Siikavuopio at Nofima.
"It will probably be able to operate more efficiently when the operators gain more experience. But before we can draw too many conclusions, the ROV needs to be tested under different conditions."
Experienced divers can harvest significant quantities in one day and in previous trials have proven to be more efficient than other harvesting tools. But diving has its limitations. It is very resource intensive and can be risky.
"An ROV will be more independent with respect to season, water currents and wave conditions, depth and other factors that limit diving," says Siikavuopio, adding:
"Using an ROV also avoids having humans in the sea and thereby entails less risk. But this system demands a high level of competence for operation, maintenance and trouble shooting."
After harvesting, the sea urchins are stored and raw enhanced for three weeks. The scientists did not find significant differences in survival or gonad growth based on the method of harvest.
The ROV was developed by Are Hofstad from Sandnessjøen-based company 7S-Technology AS.
The full-scale trial was financed by the Fisheries and Aquaculture Industry Research Fund (FHF) through the Research programme for lesser-utilised resources (LUR).