Suitability modelling for offshore cultivation of Macrocystis pyrifera in Australia’s southern waters

Seaweed aquaculture offers many benefits that may be enhanced by shifting from onshore to large-scale, offshore cultivation. However, the feasibility of offshore cultivation in extreme conditions and at low surface-nutrient concentrations is a major knowledge gap. This project identified potential offshore sites in Australia’s southern waters for cultivation of Macrocystis pyrifera, a valuable, fast-growing kelp. We created a species distribution model to understand the mechanisms that influence M. pyrifera growth on Tasmania’s east coast and found that higher productivity, and lower bathymetry and salinity were the most important variables for predicting its nearshore presence. We then combined our results with expert knowledge in literature, to create a fuzzy logic model containing 15 layers of climate, biological, and chemical data from the surface and up to -1,000 m. Using a scale of ‘least’ to highest’, we produced maps showing the relative suitability of offshore locations with different aquaculture systems at varying nutrient depths. We found that waters near the South Tasman Rise, the East Tasman Plateau, and Tasmania’s southwest had the highest suitability and may indicate the existence of nutrient traps created by steep rises supporting local Orange Roughy populations. We recommend future field analysis of these promising sites.