Hananui Aquaculture Project water quality assessment
- Client Name
- Ngāi Tahu Seafood Resources Limited
- Location
- Te Ara a Kiwa / Foveaux Strait, New Zealand
Challenge
Aquaculture will play a key role in sustainable food production as populations increase. For Ngāi Tahu Seafood Resources Limited, the Hananui Aquaculture Project provided an opportunity to support the development of New Zealand’s aquaculture industry through open-ocean salmon farming in the high-energy waters of Te Ara a Kiwa / Foveaux Strait, off the northern coast of Rakiura / Stewart Island.
Ngāi Tahu Seafood Resources Limited required an assessment of potential water column effects to support the fast-track consenting process. This included whether farm-derived nutrients could influence water quality or phytoplankton, whether fish respiration could reduce dissolved oxygen concentrations, and how to monitor and manage these effects.
The dynamic receiving environment added complexity. SLR’s challenge was to interpret baseline data, published science, and modelling outputs in a way that was technically sound, proportionate to the expected level of effect, and clear for decision-makers.
Solution
Our team prepared the water column assessment for the Hananui Aquaculture Project, acting as lead author for water column effects. The assessment characterised the existing receiving environment and evaluated potential effects on water quality, phytoplankton, and dissolved oxygen.
Our team drew on baseline water quality data, published science, and hydrodynamic and water quality modelling, undertaken in partnership with Oceanum, to understand how farm-derived nutrients and oxygen demand would behave in the high-energy conditions of Te Ara a Kiwa / Foveaux Strait. The modelling assessed the proposed development stages, including potential changes in water column nutrients and dissolved oxygen associated with the farmed salmon.
SLR translated these technical inputs into an assessment of effects and recommended monitoring to verify that nutrient concentrations, phytoplankton responses, and dissolved oxygen conditions remained consistent with model predictions. This provided a basis for managing water column effects through the proposed adaptive management framework.
Impact
The Hananui Aquaculture Project application was granted in August 2026, enabling Ngāi Tahu Seafood Resources Limited to progress a significant open-ocean aquaculture project.
Our water column assessment helped demonstrate that predicted effects on water quality, phytoplankton, and dissolved oxygen would be low and localised, with the high-energy conditions of Te Ara a Kiwa / Foveaux Strait providing substantial dilution and flushing. The assessment also helped define monitoring requirements to verify that actual effects remained consistent with model predictions.
By combining baseline monitoring, published science, hydrodynamic and water quality modelling, and monitoring recommendations, SLR provided decision-makers with a technical basis to understand and manage water column effects through the project’s adaptive management framework.
