World Aquaculture December 2020

58 DECEMBER 2020 • WORLD AQUACULTURE • WWW.WA S.ORG only lead to more profitable farms, but higher environmental standards as well. The Benefits of Submerged Feeding Water-borne feed systems with feed delivery lines installed at depth can survive high energy environments and enable farmers to deliver feed to submerged pens, a capability that air blown feeding systems do not have. As with any system, water-borne feed systems have advantages and drawbacks. Delivering feed below the surface keeps fish out of surface waters where parasite levels are the highest. Water, as a denser medium, provides a smoother ride as pellets traverse the feed distribution system, reducing pellet damage. Pellets moving at high velocities with air blown systems will rattle around in the feed pipe causing small chips and cracks in the pellets. These fine particles may be small, but over a year, can accumulate into thousands of dollars of wasted feed. In addition, as soon as pellets enter the water, they start to become saturated and water-soluble nutrients start to leach out. The high lipid content of salmon feeds makes them hydrophobic, reducing water penetration of the pellet and slowing the process down. After several minutes in water, the feed has lost some of its nutrients. Suppliers of water-borne feed systems have reduced these impacts by shortening feed delivery times and minimizing the turbulence created from pipe fittings and corners. Despite the benefits of submerged pens and advances in underwater feeding technology, they still exacerbate certain challenges, particularly with regards to feeding. Specifically, if an operator can’t see the fish, how does one knowwhat rate to feed them or when to stop feeding? New tools for observing and understanding fish feeding have allowed farmers to make informed feeding decisions without directly observing their fish. Cameras inside a pen can provide real-time A quaculture is a business of slimmargins and large volumes. Every percentage point of efficiency is multiplied over thousands of tonnes of production to lead to significant impacts on the bottom line. This is especially true for feeding. It is the most crucial farm operation and typically requires the most boat time and labor. Often it accounts for 60 percent or more of a fish farm’s operating costs. The importance of efficient feed systems and feed system operators cannot be overstated. A typical farmmight produce 5,000 t of fish per year and have a feed conversion ratio (FCR) of 1.5 to 1. With an average feed cost of $1,800/t, this farm’s annual feed budget would be around $13.5 million. Improvement in feed efficiency by 1 percent would save approximately $135,000 each year. As the world’s demand for fish-based protein increases, so does the demand for new technologies to address industry challenges. Companies are looking to locate their farms in deeper waters and higher energy environments to achieve larger economies of scale and avoid conflicts with nearshore ocean uses. However, with more exposed locations, pens and farm systems need to be designed and built strong enough to withstand the punishing forces generated by serious storms. Submerging equipment dramatically reduces the kinetic energy it is subjected to in the open ocean. Pens and infrastructure just 15 m be- low the surface will dissipate almost all wave energy, nearly eliminating the rubbing, chafing and stress that causes the high-cycle fatigue that leads to early retirement of system components or even failure. In addition to reducing wave energy, submerged pens minimize parasite exposure, help moderate water temperatures and make it easier to avoid algal blooms. This makes them an attractive option for many areas. While not an entirely new concept, complementary technology and submerged feeding systems make submersible farms much easier to operate and more cost effective. Innovative solutions that help reduce feeding costs and increase farm sustainability not How Submersible Pens and Submerged Feeding Systems Are Revolutionizing Aquaculture Tyler Sclodnick, Thomas Selby and Langley Gace Submerged pen can be sited in locations typically not considered due to high wave energy and strong currents. By moving feed system infrastructure beneath the surface, feed operations will remain uninterrupted, whatever the conditions at the surface.