Giant, instrumented pens will monitor the health of millions of fish and feed them automatically
Tucked within Norway’s fjord-riddled coast, nearly 3,500 fish pens corral upwards of 400 million salmon and trout. Not only does the country raise and ship more salmonoid overseas than any other in the world (1.1 million tons in 2018), farmed salmon is Norway’s third largest export behind crude petroleum and natural gas. In a global industry expected to quintuple by 2050, farmed salmon is a fine kettle of fish.
But raising salmon is not without its challenges. Feeding them makes up half of all operational costs. Parasitic crustaceans called sea lice (Lepeophtheirus salmonis) make easy meals of captive fish, attaching to their bodies by suction and grazing on skin, blood and mucus. If they don’t kill the fish, some delousing methods, such as flushing fish with water, might. About 15 percent of farmed salmon die in traditional fish pens and sea lice cost the salmon industry several billion dollars annually, according to Norway Royal Salmon.
A new remote-controlled fish pen—the first of its kind designed for the tempestuous waters of the open ocean—could help Norway meet the growing demand for salmon and at the same time reduce the cost of feed and mortalities that result from sea lice.
Instrumented with wireless gauges, sensors and cameras, the sea pen will give workers onboard a nearby barge the ability to monitor the fish, automatic feeders, and a remotely operated net cleaner as well as environmental and meteorological conditions, such as water depth, turbidity, salinity, oxygen, temperature, echo locators, and pH levels. The underwater feeding system reduces the energy cost of feeding by 50 percent. And because these open ocean pens will keep salmon 10-40 meters beneath the surface, below the sunlit zone where sea lice and algae thrive, they could reduce or eliminate the need for delousing operations, significantly lowering mortality rates.
Initial testing of the first pen will happen in 2020 off the coast of Troms, near a small island that will help dampen the rough waves. After seeing positive results from field trials, the pens could be moved further out to sea.
The system, developed by Arctic Offshore Farming (owned by Norway Royal Salmon), is a cylindrical fish pen with an outside diameter of 79 meters. Resembling a giant fish basket, the structure has a top and a bottom section, 10 meters apart. Each has a buoyant pontoon ring, supported by 16 columns. When submerged, only the upper pontoon is visible on the ocean surface. The salmon live in the bottom section, in a large net that drapes to a depth of 40 meters from the lower pontoon. A roof net prevents the fish from swimming into the top section and can be removed to either add fish or harvest them.
Stability is important, not only for maintaining structural integrity of the pen, but also for the health of the salmon. Fish need access to air to fill their swim bladders in order to maintain and control their buoyancy. To accommodate them, the pen has four decompressors, each in one of the support columns, that create air pockets beneath the water. A camera and oxygen sensor at each column will monitor the air pockets and automatically engage decompressors to keep them full at all times. A less stable pen would not be able to maintain such reliable air pockets, says Klaus Hatlebrekke, Chief Operating Officer of Markets and Business Norway Royal Salmon. “Even in a model test of a 50-year storm, we were not able to disrupt the air pockets,” he says.
The cameras are also used to monitor the net for wear so that repairs can be made before salmon escape.
As with traditional salmon farming, the salmon will be raised from egg to juveniles, called smolts, onshore in freshwater hatcheries. After about a year, the smolt, weighing about 100 grams, will be transferred to a saltwater sea farm in a fjord. Under conventional methods, they would stay in the fjord and be raised until they weighed 5 kilos, says Hatlebrekke. But with the new system, fish weighing 1.5 kilos will be moved to the open ocean pens, where they’ll remain for another 10 to 11 months before they’ll be harvested. With a volume of 120 cubic meters, the pen can hold up to 600,000 full grown salmon at a time.
Using a local area network, the sensors will transmit their data to an onboard server that’s connected via a fiber optic cable to a crewed feed barge stationed about 400 meters from the farm. One barge is capable of monitoring a cluster of fish farms and restocking them with feed pellets about every seven to 14 days.
The automatic feeders on the pens use 50 percent less energy than the system employed by traditional fish farms. Current systems blow feed pellets through air hoses floating on the water’s surfaces. But a similar approach cannot be used in the open ocean where tall waves and winds would scatter the feed out to sea. Instead, the new system automatically releases the feed underwater one to three times per day, allowing the currents to distribute the pellets. Four additional cameras allow crew members on the barge to see where the fish are located and release feed in their area, reducing waste.
Although jobs in salmon fishing are about to get more technical, they don’t have to be complicated, says Lars Andersen, a sales specialist in Aquaculture at ABB. The company built a user-friendly interface that displays the controls and safety systems in a simple dashboard. A telecommunication link to a control base onshore offers land-based operators access to the pens, as well.
For the fish, their experience will more closely represent a life lived in the wild, says Hatlebrekke. Wild salmon that begin their journey in freshwater rivers spend only a few weeks in the sheltered fjord waters before they swim out to the open ocean. As farmed salmon operations incorporate more technology, the lives of farmed fish could mimic the path from freshwater to open sea, giving them a more natural existence.