The University of New Hampshire (UNH) presently holds two adjacent offshore aquaculture permits with a total area of 52.6 hectares. The permitted sites are approximately 5 km from shore in a depth of 35 m of water. At this location, UNH is licensed to grow and sell several species of shellfish and macro-algae. Being offshore, however, aquaculture systems must be designed to withstand extreme events and to minimize harmful interaction risk that exists with large marine mammals, especially, the North Atlantic right whale (NARW).
The objective of this presentation is to describe the engineering procedures for the whale-safe design of an offshore kelp farm. The approach builds upon the experience of two successful, smaller kelp farm deployments, using (1) composite rods as a replacement for mooring rope, (2) high density polyethene (HDPE) pipe as a kelp growth substrate and (3) weak links attached to specific flotation elements. The offshore kelp farm design incorporates a planar assembly for near-surface kelp growth on HDPE pipe, pretensioned with components having bending resistance, like the composite rods described in [1]. The composite rods were also used in the mooring components as a rope replacement. The system design for the UNH offshore site utilized wave and current parameters described in [2] with a kelp aggregate modeling approach validated in [3]. The presentation will also describe the application of a preliminary whale loading numerical routine applied to this specific structure. The intent was to design the offshore kelp farm to satisfy the tenets of the Marine Mammal Protection and Endangered Species Act and to yield up to 12,000 kg of fresh product, while absorbing coastal nutrients.
[1] Gitelman, L., Moscicki, Z., Patwary, M.M.R, Zhu, L., Chambers, M., Fredriksson, D.W., Swift, M.R., Tsukrov, I. 2024. Utilization of Semi-Rigid Composite Lines for Whale-Entanglement-Safe Aquaculture Farms. Proceedings, Oceans 2024. Halifax, Canada. 7 p.
[2] Sunny, R.C., Fredriksson, D.W., Tsukrov, I., Zhu, L., Bowden, M., Chambers, M., Silkes, B. 2024 (in revision). Design considerations for a continuous mussel farm in New England offshore waters. Part I: Development of environmental conditions for engineering design. Aquacult. Eng.
[3] Zhu, L., Patwary, M.M.R., Sunny, R.C., Tsukrov, I., Fredriksson, D.W. 2024. (in Revision). Hydrodynamic modeling of kelp (Saccharina latissimi) Farms: From an aggregate of kelp to a single line cultivation system. Ocean Eng.