Accessible aquaculture - Hongoeka Development Trust
Māori participate in all aspects of the seafood industry, but Māori involvement in the aquaculture industry is less than it should be. The barriers to greater involvement include high capital costs and long lag-times before profits are realised.
NIWA collaborated with Hongoeka Development Trust Ltd to develop a proposal for a community-based aquaculture project on their land at Plimmerton. This research programme used polyculture technologies to develop economically sustainable systems that make aquaculture more accessible to Māori.
The idea of an aquaculture-based venture was built around the concept of a pāua or abalone farm, where the waste was recycled to produce other high value foodstuffs. This concept had been applied to other systems worldwide, but had never been used where abalone were the main producer of waste within the system.
The highly experimental and innovative nature of the project meant it attracted funding from the Foundation for Research, Science & Technology (FRST). The project, within Hongoeka's overall plan, is one part of a planned tourism, training and hatchery venture.
This research succeeded in designing a robust, low cost, low maintenance system based on novel recirculation technology.
The self-cleaning abalone tanks mean relatively constant input of suspended solids. The large suspended solids are removed using a simple settling basin (bioclarifier) which requires cleaning only every three weeks, while the fine suspended solids are removed by foam fractionators.
Initial species selection was based around pāua coupled with species that were both relevant to Māori and could thrive in the same system. The final species trialled were pāua, karengo (removes dissolved ammonia), oysters (remove suspended solids) and sea cucumbers (remove settled solids).
- Pāua: grew well (2-3 mm per month was common) in the pilot system initially tested at NIWA’s Mahanga Bay Aquaculture facility. This is as good as any other farm in New Zealand and better than most. Growth rates in this recirculation system are better than in flow-through systems. However, more attention has to be paid to removing waste products and maintaining pH levels.
- Oysters: did not live in the system and were replaced by mussels.
- Mussels: the filtering capacity of mussels is quite high and very few were needed to reduce the suspended solids load. Estimated capacity was just a few kilograms: not enough to warrant any meaningful harvest from the system.
- Sea cucumbers: research showed that this species, whilst efficient at eating settled solids and able to grow on waste from pāua fed a natural algal diet, would not survive on the waste produced by pāua when the pāua were fed the artificial diets that are used in NZ. Some very useful data on sea cucumber energy budgets was derived, but they could not be included due to their inability to eat the solids in the system.
- Seaweed: we have tested two species of red seaweed, Porphyra (karengo). Both can be cultured within the system and will remove some of the ammonia from the water. We are still investigating growth and ammonium uptake at various temperatures.