Construction of a Double-Net Integrated Multi-trophic Aquaculture Raft for Steelhead Trout and Blue Mussel Aquaculture

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M. Robinson Swift UNH - Department of Mechanical Engineering Principal Investigator

Funds are requested to engage fisher support by upgrading construction of a single net-pen integrated, multi-trophic aquaculture (IMTA) raft to a double net-pen system. The raft will be used as the basis for new proposals for fish feeding and harvesting technology and education programs for underemployed fishers to learn aquaculture techniques. The raft will be operated by the N.H. Trout Growers at the UNH permitted site off New Castle, N.H.

A grant from National Marine Fisheries Service, Saltonstall-Kennedy (S-K) program, has been secured to design, build and test an all-season, single net-pen raft for growing steelhead trout and blue mussels. The rationale for this approach is that nitrogen and other nutrients released by the fish would be more than compensated by uptake by the mussels. This is not only an environmental plus, but also enables farm permits to be obtained more easily. With support of this grant, the design shown has been developed. Sufficient funds to build this design were included in the S-K grant.

The fishers that will eventually use this system, however, have stated that it would be even better for their purposes if the size were doubled. The continuous, double net-pen design would replace two existing, single net-pens that are old and in poor condition. The replacement system would be much stronger since the lashed and tire fendered joint between the two existing rafts would be eliminated.

The double net-pen design will serve as a platform for further technology development and education. Proposals will be written for automatic feed distribution and storage systems, as well as fish harvesting aids. A proposal for training new groups of fishers has been submitted to S-K, and follow-up proposals are planned. This system will become the centerpiece of UNH aquaculture extension activities. The success of any cooperative work with local fishers depends on their enthusiastic support, and the upgrade to the double net-pen raft is a critical component of that relationship.

Regarding funding considerations, the $20,000 budgeted from the existing S-K project is enough, with UNH labor, to build the single net-pen design. With simplifications and economies, the double net-pen design can be built for about $32,000. These figures are based on costs and quotes supplied by JPS Industries, Bristol, N.H. The PI’s are able to contribute $5,000 towards the additional $12,000 needed. We, therefore, request $7000 in Sea Grant development funds to complete the improved design.