Tuna Trap & Transfer Programme

Tuna are a taonga species for Māori, and are arguably one of the most important mahinga kai species. Historically they were an important food for Māori - they were widespread, abundant and caught fairly easily, providing a source of protein, fat and oil in the diet.

The Trust had an important and early input into developing a native tuna (eel) trap and transfer programme for the Waiau Catchment in conjunction with Meridian Energy Limited. The programme is stationed at the Manapōuri Lake Control Structure (elvers) and in Lake Manapōuri (migrant transfer). The programme continues with its day to day management now undertaken by Meridian Energy. The purpose of the programme is to ensure the sustainable management of tuna biomass in the catchment and provide adequate native fish passage where it is constrained by hydroelectricity infrastructure.

Tuna facts and figures

The Te Waiau Mahika Kai Trust is focused on rejuvenating mahinga kai opportunities in the Waiau Catchment with a particular focus on native fish species including tuna (native eels - both shortfin and longfin species).

Native tuna start life near Tonga. Eggs hatch into larvae which are transported to New Zealand shores on the ocean currents. The larvae turn into glass eels and enter estuaries, rivers and streams. The glass eels in turn grow into elvers over a 3-5 year period. The elvers migrate up the Waiau River and over a 40 – 80 year period grow into adult eels. They ultimately reach a stage in their lifecycle where they migrate back to Tonga to breed.

The Trust in it’s early days led an effort to improve tuna passage in the Waiau Catchment that was constrained by the structures associated with the Manapōuri Power Scheme. The primary point of constraint is at the Manapōuri Lake Control structure (MLC) located at the confluence of the Waiau and Mararoa Rivers. It was here that early efforts were focused in trapping the elver as they arrived at the structure and then transferring them throughout the Upper Waiau catchment including Lake Manapōuri and Lake Te Anau.

Over time the programme has extended to trapping the migrant tuna in Lake Manapōuri and releasing them below the Manapōuri Lake control structure. The purpose of this programme is to reduce the likelihood of migrant tuna mortality as a consequence of the tuna entering the intakes of the Manapōuri Power Station at West Arm.

Meridian Energy, on behalf of the Trust and Ngāi Tahu, now manage the trap and transfer programme and reports annually on its results, as shown below. The Trust will continue to monitor the outcomes of this programme and identify opportunities to add value to it through direct contact and discussion with Meridian Energy Limited.