Stepping up for native fish
The idea of installing ladders for something without arms or legs may seem a little crazy - but for Whangarei’s threatened native fish it might literally prove a life saver.
The small, simple stainless structure can make a huge difference to the long term survival of native fish species.
The ladder enables fish to pass around obstacles or barriers by swimming and leaping up a series of relatively low steps to reach the water on the other side.
More than two-thirds of New Zealand’s 35 native fish species are classed as threatened or at risk, and many of these need to migrate hundreds of kilometres between rivers and streams and the sea to reach suitable spawning areas.
While some fish like banded kokopu are strong climbers and able to negotiate natural barriers like waterfalls, other obstacles, especially man-made ones, can stop them reaching critical habitats altogether.
Northland Regional Council’s freshwater ecologist Carol Nicholson says all too often migrating fish encounter obstacles in the form of culverts, weirs, tide gates, dams or other man made structures.
Nicholson says both the Department of Conservation and regional council have legal responsibilities to manage fish passage in waterways.
Since 1985 any structure that could impeded fish passage requires a permit, but older structures, many linked to historical flood protection work, were installed before the knowledge about fish cycles was known.
The council is working to remove possible barriers.
Championed by the Whangarei Harbour Catchment Group, a fish ladder was recently installed into the Kirikiri Stream culvert under Whangarei’s Western Hills bypass.
Nicholson says the ladders can make a huge difference to the long term survival of native fish species.