Study of a Three Point Mooring of an Open Ocean Aquaculture Feed Buoy

Abstract

Open ocean aquaculture will be important in supplying fish as natural fish stocks decline due to environmental changes and overfishing. However, the technology needs to be developed to provide the equipment and methodology for such offshore operations. The University of New Hampshire has been developing and testing systems in the open Gulf of Maine, and has a number of years experience with a feed buoy moored to a fish cage via a stretch hose and elastic tethers. This configuration has survived the Gulf of Maine currents and waves, and continued to feed fish autonomously. The unique tri-mooring is studied via modeling, and observing the wear and behavior for years. The system is robust and has functioned well over the years and is a good candidate for aquaculture operations. I. INTRODUCTION The University of New Hampshire (UNH) has been developing the technology for open ocean aquaculture over the last decade at a site offthe Coast of New Hampshire in 52 m of water in the open Gulf of Maine [1]. Several different size and types of fish containment cages have been deployed and evaluated at the site [2, 3, 4]. A major part of an aquaculture operation is feeding the fish with the goal of optimizing the amount, rate and timing of feeding events for fish growth. An open ocean aquaculture operation is quite different than sheltered operations due to the increased environmental forcing (currents and waves). To develop offshore feeding capability, a feed buoy was designed [5], constructed and moored to a submerged fish cage by a compliant stretch hose [6] and elastic tethers [7]. This tri-moor is necessary to allow the feed buoy to move with surface waves, yet decouple its motion from the fish cage that is nearly stationary at a depth of approximately 10 meters. Feed is stored in the buoy and pumped into the cage via the stretch hose, under control of the buoy computer system. A study of this coupled feed buoy, fish cage and mooring system is presented as a possible successful configuration for open ocean aquaculture operations.