by Elizabeth Heeg, Freshwater Manager
Our freshwater fish are unique, interesting and essential to New Zealand’s biodiversity. We just need to get to know them better.
What about the fish without bones? Kanakana/lamprey (or pirahau as they’re known in some parts of New Zealand) has only cartilage. This living ancestor has survived 360 million years without jaws (a sucker-like mouth does the eating instead), paired fins and proper bones.
Despite these apparent disadvantages, kanakana have a lot going for them. Kanakana live in river sediment before turning a vivid blue colour and migrating to the sea. There, kanakana survive living parasitically off marine life until they become adults. When ready to spawn, they journey back to freshwater, and the cycle can begin again.
Galaxiid species are more familiar, although many of us encounter them as whitebait – the juvenile īnanga, banded kōkopu, giant kōkopu, kōaro and shortjaw kōkopu. The family name galaxiid comes from the fact that some adult galaxiids have star-spangled skin, like a galaxy.
Tuna or longfin and shorfin eels are also pretty familiar. But they’re a surprise too. Tuna can live for over 100 years old and are one of the few fish species able to swim backwards.
These are just a few examples of New Zealand’s 51 native freshwater fish species. Many are found nowhere else in the world. Twenty-two are threatened with extinction. Many need to move within our waterways and between freshwater and the sea. If their movement up and downstream is delayed or blocked completely, fish may not be able to get to the habitats they need to complete their lifecycle.
Adult kanakana for instance can suction onto surfaces to move upstream to migrate within our waterways and find spawning habitat. This means they can navigate over and through a number of our instream structures. However, some structures are trickier to overcome – kanakana often fall off instream structures with sharp edges, which prevents access to the habitats they need to complete their life cycle.
Instream structures like culverts and dams can be a problem for our fish. Disconnections between the water upstream and downstream of a structure can stop or slow down fish passage. This can be caused by culverts with a significant drop at the downstream end, extremely long structures, perched (undercut) structures, fast water flow through a structure and weirs that are too high for fish to navigate.
For this reason, it’s important to ensure instream structures allow passage for our precious native fish. A series of freshwater fish videos shows how different native fish swim, climb obstacles, and why some structures in streams are barriers to their migration to the sea and back. For kanakana, it means building structures with curved rather than sharp edges.
We need to get out there and identify fish passage barriers in our waterways and fix them. Anyone can help out. NIWA, with the New Zealand Fish Passage Advisory Group, has developed a handy fish passage assessment tool perfect for citizen scientists, to identify and record barriers to fish passage when out and about. A new fish passage assessment tool video developed by DOC and the New Zealand Fish Passage Advisory Group provides information on freshwater fish, the problem with in-stream barriers and how to use the fish passage assessment app.
We’re also the first country to greet World Fish Migration Day which is a one-day global celebration to create awareness on the importance of free flowing rivers and migratory fish. While the official day is the 24th October, some events have been run throughout the month of October. There will also be educational events around the country over the next couple of days. They’re a great opportunity to get the whānau involved in protecting our precious native fish.
Spread the word, tell people about our amazing fish and download the app – it’ll help us achieve more freely-flowing rivers and streams where fish can live their entire life cycle without barriers.
For more information on fish passage or to check our other cool resources see www.doc.govt.nz/fishpassage