Fish access
Many of our native fish need to travel between freshwater wetlands and the sea to complete their life cycles. Structures such as over-hanging culverts and dams can block fish passage. There are simple ways to help fish access wetlands.
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Many of New Zealand’s native freshwater fish live in wetlands for some or all of their lives. Short and longfinned eels, inanga, giant kokopu and banded kokopu all live in or use our Region’s wetlands. These fish also make long journeys to and from the sea using a corridor of rivers, streams and drains. This watery pathway must be kept intact for them to complete their life cycles successfully.
Wetlands are also home to our native freshwater crab, pea mussel and shrimp. Find out more about freshwater animals and plants.
Whitebait
The juveniles of five of our native fish – banded, giant, and short jawed kokopu, inanga and koaro – are collectively known as ‘whitebait’. Most of the whitebait fishery catch is inanga. Every autumn, adult inanga spawn in the grassy stream margins upstream of estuaries. The eggs hatch a month later and the larvae are washed out to sea. Six months later they make the hazardous return journey back to freshwater as juveniles.
Juvenile kokopu and koaro may migrate over 100 kilometres upstream, even climbing damp rocks alongside steep waterfalls, until they reach sheltered streams or wetland habitats.
What native fish need
Wetlands connected to streams at least 10 cm deep will be accessible to most native freshwater fish. But long stretches of fast flowing or polluted water, flap gates, or over-hanging culverts are impassable barriers.
Native fish also need streams with fairly clear water, shading and cover. Muddy water limits their vision and reduces their food supply of aquatic insects.
Environment Waikato seeks to maintain fish access through our policy and plans. Check out the Fishery Class water rules in our Proposed Regional Plan.
Simple solutions
Help fish find your wetland using the tips below.
- Set stream culverts low in the stream bed, placed horizontally.
- Rough up the smooth bottom of culverts with cement or rocks to slow water flow.
- Some juvenile fish are able to climb wet surfaces. A flexible corrugated pipe with water trickling through it can help fish to travel short distances between two wetland areas that have no natural fish access.
- Plant overhanging species like flax and sedges for shelter and to keep the water cool.
- When clearing drains, leave one side or parts of it untouched until plants have grown back.