Science Centres: Fisheries

Graeme Moss with some of the paua. We are testing several tank designs.

NIWA’s world-first polyculture system based on paua is now operating as a prototype.

Polyculture involves two or more complementary species growing together in a single sustainable system; in this case, paua, tio (Pacific oysters), sea cucumbers, and karengo (a seaweed). The venture is a joint project with the Hongoeka Development Trust, and aims to develop a low cost way for coastal iwi to engage in land-based aquaculture. The tio and sea cucumbers feed on particulate matter produced by the paua, while the karengo removes some of the excess nutrients from the system.

The prototype, at one-quarter of full-scale, is housed at our Mahanga Bay aquaculture facility in Wellington. As far as we are aware, this is the only polyculture system in the world which does not incorporate fish. Another unique feature is the use of biofilters to convert ammonia to less harmful nitrates, which reduces the amount of seaweed required to ‘clean’ the system.

The system has highly efficient protein skimmers, designed at Mahanga Bay. Protein skimmers pull dissolved protein out of the water. Unlike conventional ones, these work on very low water pressure and do not require any extra power.

We will begin construction of a full scale, pilot system at Hongoeka later this year, but continue to run the prototype, mapping the flow of nutrients through the system and improving the design. The final system is intended to produce about 1 tonne of paua per year.