Conservation Corner – NZ’s Native Fish!

Our native fish

Whilst secretive and not as showy as kākāpō, our 35 species of native freshwater fish are fascinating and an essential part of our biodiversity and eighteen of them need to move between freshwater and saltwater to complete their lifecycles.

Kanakana (lamprey) are ancient (360 million years old) and have no bones or jaws (only cartilage and a sucker-like mouth). The young live in the sediment of rivers before they turn bright blue and head out to sea. In the ocean they latch on to other fish and drink their blood until adulthood when they return to freshwater to spawn.

There are also migratory Galaxiid species, so named because their skin patterns look like galaxies of stars. Adults travel downriver to spawn in river mouths juveniles then swim back up the rivers, and, if they avoid our whitebait nets, start the cycle all over again. The Nevis galaxias was instrumental in preventing a dam on our beloved Nevis River.

Tuna (longfin and shortfin eels) can live for over 100 years. As tiny elvers, they journey up streams. After many years (sometimes up to 80 for longfin eels) they migrate to the Pacific Ocean where they breed and then die.

For all these species, it is crucial that they can move freely within and between their freshwater and marine habitats to complete their lifecycles. Manmade structures that physically block or change the natural flow of rivers and streams can get in the way of this migration. Some species are more affected than others for example īnanga are weak swimmers and can’t climb while kōaro and eels are surprisingly good climbers and can make it up even vertical surfaces. Adult kanakana put those suckers to good use suctioning onto surfaces though they are often thwarted by sharp or overhanging edges. Watch it for yourself here.

So what can you do to help?

You can identify these barriers and record them so that they can be fixed. It is as easy as downloading the fish passage assessment tool. Then, next time you’re out for a paddle, keep an eye out for culverts with a significant drop, undercut or extremely long structures, fast water flow through a structure or weirs that look too high for fish.

Spread the word, do it for the fish and the whitewater.

Jacqui Tizzard
WWNZ Conservation Officer