What's Happening to Our Ika?
- 6 days ago
- 2 min read
A Global Collapse, Reflected in Native Fish Here in Aotearoa.
A major new report from the United Nations Convention on Migratory Species has delivered a stark finding. Migratory freshwater fish populations have declined by roughly 81% since 1970. The species facing collapse all share one thing in common: they depend on rivers that are connected, unobstructed, and able to carry them between freshwater and the sea.
Aotearoa New Zealand has been living this story for decades.
Of our 51 native freshwater fish species, most are migratory - and many are diadromous, moving between rivers and the sea to complete their lifecycles. Tuna, īnanga, kōaro, shortjaw kōkopu, kanakana are species that must move. Their survival depends on access and the ability to travel from river headwaters to coastal waters and back again. 76% of our indigenous freshwater fish species are threatened with extinction or at risk of becoming threatened.
Tuna - the longfin eel, found only here - is perhaps the clearest case.
Longfin eel populations are declining across Aotearoa. Dams, weirs and culverts create barriers that prevent tuna from colonising upstream habitats and completing their lifecycles. Many dams have blocked the longfin eel's access to the sea across its habitat. When a species needs decades to reach reproductive maturity - some female longfin eels are estimated to be more than 90 years old - every barrier, blocked culvert and degraded stretch of river compounds the problem across generations.
Īnanga face an equally serious set of pressures.
Classified as At Risk – Declining, īnanga (whitebait) need to move freely between freshwater and the sea to complete their lifecycle, yet many are blocked by culverts and weirs. Their eggs need riparian plant cover to survive and juveniles need clear passage to the sea. Remove any part of access to these things, and the population cannot hold.
The global report makes a point that applies directly here: protecting migratory fish requires managing rivers as connected systems.
Here in Aotearoa, we can extend that further. We need to manage habitats as connected ecological and cultural systems. Tuna, kōaro, kanakana - these are taonga. Iwi and hapū have tracked their presence, abundance, and movement for generations. This knowledge reflects the same collapse science is now documenting in numbers.
The solutions are known and include:
Fix and remove barrier culverts.
Restore riparian margins.
Ensure environmental flows actually move.
Protect the lowland streams where īnanga still spawn.
There are awesome iwi and locally-led and water restoration projects underway across the motu. DOC's Ngā Ika e Heke programme, which began in 2019, also provides a national approach to managing migratory fish - covering shortjaw kōkopu, īnanga, tuna and kanakana. working alongside iwi, hapū and regional councils.
This work needs resourcing and scale to match the crisis.
The global 81% figure is a signal that we need to take more urgent action. Our ika are telling us the same thing our rivers are: connectivity is survival.
