Investigation of native southern Australian seaweeds with potential for use in Integrated Multi-Trophic Aquaculture

Integrated Multi-Trophic Aquaculture (IMTA) is gaining attention worldwide as a system by which multi-species aquaculture can be conducted to yield environmental and economic benefit. IMTA is of interest in South Australia... [ view full abstract ]

Integrated Multi-Trophic Aquaculture (IMTA) is gaining attention worldwide as a system by which multi-species aquaculture can be conducted to yield environmental and economic benefit. IMTA is of interest in South Australia (SA) where two species of finfish are cultured and stocking levels are regulated to ensure nutrient outputs are within the carrying capacity of the environment. Co-culture of seaweeds in these areas has the potential to ensure environmental impacts of aquaculture are minimized while producing an additional crop, but seaweed farming in Australia is yet to be commercialized, and few native species have been farmed. Seaweed species used in IMTA should be native to the area, have commercial value, and grow large and fast enough to be commercially viable and remove sufficient nutrients. Native species with desirable characteristics, i.e. large potential size and commercial value, were identified by a literature review, and their growth rates and nitrogen content investigated in laboratory and field experiments. Four Rhodophyta including two agarophytes (Gelidiales), a carageenophyte (Solieriaceae), and Plocamium angustum, a desirable feed for abalone, were grown in laboratory experiments at nutrient levels expected in aquaculture zones; these and four Phaeophyceae that are potential sources of alginates, fucoidan and bioactive metabolites (three Fucales and the common kelp Ecklonia radiata) were also grown in the field to compare their performance and investigate seasonal changes. Growth rates and nitrogen content were used to estimate the nitrogen removal potential of each species. Reproductive techniques and temperature and light responses of selected species were also investigated, and the best performing species used in a seaweed aquaculture trial around yellowtail kingfish farms in Port Lincoln. This presentation will summarise the results of these studies and discuss the next steps towards developing IMTA in Australia.