Abstract
Offshore aquaculture is rapidly gaining momentum, driven by the need to address environmental concerns associated with nearshore aquaculture and to mitigate conflicts over coastal water usage among local communities. This keynote paper introduces a novel offshore fish cage design called the SeaFisher. This fish cage is designed to overcome the challenges of fish farming in offshore environ-ments, characterized by strong waves, deep waters, rapid currents, and high winds, especially in storm events. The SeaFisher consists of a 2 x n array of interlocking modular cubic fish cages. Each cubic cage frame is constructed from members formed by bundling four high-density polyethylene (HDPE) pipes, and stiffened by diagrid glass fibre reinforced (GFRP) rods. The HDPE pipes are secured by regularly spaced pipe bundling brackets and at the joints by connector pods. Sup-ported by aluminium tubular frames, the pyramidal shaped top and bottom nets provide air space for salmon jumping and for easy removal of fish morts, respec-tively. Vertical aluminium ballast tubes, located at the top corners of each cage, allow the SeaFisher to submerge to avoid strong surface waves during storms and to resurface after the storm. The ballast tubes control filling ratio automati-cally to ensure hydrostability, including compensation for additional biofouling mass. Depth control buoys manage the cage’s descent and maintain its submerged position. The SeaFisher is moored by a single mooring point (SPM) system, com-prising a buoy, hawser, studlink chain and suction anchor. This system allows the SeaFisher to weathervane; reducing environmental loads and spreading fish waste over a wider water column. Presented herein are the design details of the SeaFisher, its modelling and hydroelastic analysis using the software package AquaSim. The SeaFisher is designed to operate in a significant wave height of 7.58 m and current speed of 0.8m/s in the Storm Bay of Tasmania. With its resilient and cost-effective design, the SeaFisher is poised to revolutionize marine fish farming by facilitating the relocation of traditional nearshore farms to more expansive offshore enabling increased production of high-quality fish.