Earlier this year, a South Island rūnanga travelled to Japan to learn from experts about tuna conservation, sustainable fishing, and the cultural importance of tuna - part of efforts to revive their own local populations.
The trip reflects growing concern over the state of Wairewa and its wider catchment, once prized by Ngāi Tahu as a rich source of mahinga kai.
Te Ao Māori News spoke to members of Wairewa Rūnanga, whose area includes Wairewa, the lake’s catchment, and nearby hills and coast next to Koukourarata, Ōnuku, and Taumutu.
Iaen Cranwell says it’s vital to track the movements of the lake’s taonga species and ensure they can reach the ocean to breed.
Tuna, one of the lake’s treasured species must migrate to the sea to reproduce, with their young needing to return to the lake to grow. Other taonga species include Kanakana (lamprey) and Inaka (whitebait).
But decades of deforestation, wetland drainage, and intensified farming have pushed many of these taonga species into critical decline. Gravel and sediment from the deforested Wairewa catchment have washed into the lake, blocking its natural opening to the sea.
While machinery has been used periodically to open the lake and prevent large-scale flooding, the rūnanga has also had to hire diggers to clear shingle to reduce localised flooding- costing $200,000 in digger fees this year alone.
The neighbouring lake, Te Waihora, averages $1.6 million annually in opening costs.
Through the Prime Minister’s Scholarship Fund, Cranwell was one of eight to travel to Japan for a cultural exchange focused on tuna. There, they learnt about the Japanese people’s deep manaaki for unagi (tuna).
“I haere mātou i reira, i tirohia te whenua, i haere ki ngā whare wānanga, ngā wāhi mātauraka, he mahi rakahau e pā ana ki te unagi, kohikohi i ngā mātauraka ka hoki mai ki konei. Ko te mea nui, ko te unagi kei runga i reira ki te Hapanihi.”
Another key takeaway was the cultural and social importance of tuna in Japan.
“Kei rātou hararei mō te tuna i te raumati; ko tērā te wā tika mō te kai, i te unagi mō te kaha, mō te hākinakina, me ērā atu tūmomo mahi.
“He rāwe te haere ki reira; i tūtaki mātou ki ngā wawata maha, ngā moemoeā mō mātou me te whānau nei.”
Ko te tuna te kai wairua ki konei te kai rakatira, ko tērā i te whakaaro o Wairewa, te whakaaro tuatahi mō te kai, ko te tuna.
— Iaen Cranwell
Cranwell says they set up an apparatus called Ko Awa Ika o Wairewa, built to maintain a constant 24/7 connection between the lake and the Pacific Ocean.
“I haka mātau mō te hoki mai i te tuna, engari ētahi wā i aukati takaroa i te wahapū o tēnei kōawaawa, uaua ki te hoki mai i te punua tuna, so whakaaro mātou ka keria ki raro rā i au ki tēnei wāhi ka whakarite tētahi kōawa ika o Wairewa mō te hoki mai o te tuna mai te moana tae atu ki te roto.”
This kind of innovation was already well-established in Japan, where they observed advanced infrastructure alongside lakes, rivers, and estuaries during their tuna research tour.
At Takiritawai river, the Department of Conservation staff and local iwi have been working to guide and collect the juveniles, helping them begin their long migration back up the river. Early spring is the best time for this, as the eels are ready to travel and conditions are ideal.
The river connects the lake to the ocean and is a key pathway for older eels who leave the lake for the sea to spawn.
Raniera Wekepiri (Kaitahu, Kāti Irakehu) was helping young eels make their way home.
“We just set up this hīnaki to help out with the migration back into the roto with the glass eel from the moana.”
For Wekepiri, the work is about more than conservation - it’s a duty to his hapū and iwi, who regard the lake as a taonga.
It’s a big part of our tradition of our customary practices gathering tuna from the lake. We want to be able to look after the lake and continue on doing this mahi for the generations to come.
— Raniera Wekepiri
Looking ahead
Cranwell says securing funding for infrastructure has been challenging, in contrast to Japan, where such projects are well funded.
“Tērā pea ka haka tētahi mea ki raro rā, āhua he ngongō wai nui, āhua pēnei ka hoki mai te punua tuna mai te moana ki te roto mai i tērā mea tūmomo, engari ko tērā te mahi uaua ēnei wā, kimi pūtea, mahi rangahau hoki mō tērā tūmomo mahi.”
Cranwell, who is the Ngāi Tahu Councillor for the Environment Canterbury Regional Council, says it’s time to explore how this infrastructure could generate opportunities and jobs.
The Rūnanga is also investing in the development of an outlet canal to better manage lake levels, prevent saltwater from entering when the lake opens, and help mitigate algal blooms.
“I am now thinking about moving the shingle and putting in large pipes [that] will connect the canal to the sea and that’ll allow when the lake is closed, it’ll allow the glass eels to get in from the sea to the lake,” Cranwell said.
Last year, planning and development were supported through the Fish Habitat Fund, an initiative designed to address site-specific threats to native fish populations and provide financial backing for projects tackling these issues. The fund offers up to $100,000 annually.
