The Opihi river that runs parallel to the Arowhenua community, is an important natural and cultural feature in the locality. A great number of tributaries across the region join the Opihi in its final journey to the ocean.
After many years of overfishing by commercial fisherman and denigration from increased intensification of agricultural land use, a small group of rūnanga members of the Arowhenua rūnanga undertook to protect the local fisheries and waterways as best they could.
Once again Te Hapa o Niu Tireni became a central point to bring community, and government together to find solutions. A number of years of consultation and negotiation have resulted in a formal legislative tool to protect the local fishery. An extensive fisheries management plan has been implemented in the form of a mātaitai reserve which protects a large section of the Opihi catchment from commercial fishing activity.
The final stage of formal notification of the Mātaitai was completed in 2014.