Contributor: Tom Anderson, Wai Kōkopu Restoration Manager
The Waihī Estuary has historically provided tuna (eel) and inanga (whitebait) as a food-source for local people for generations. In the past, the wetlands that used to span from the estuary to upstream of State Highway 2, provided a massive habitat for native fish species to spawn, feed and grow.
These wetlands have now largely been lost, but schools of inanga are still seen moving up our rivers from September to November, around their spawning time.
Further upstream native species like giant kōkopu, kōaro and shortjaw kōkopu live in the fast-flowing streams and tributaries, but their numbers are few.
Fortunately, many farmers in the catchment have been restoring their streambanks and wetlands with native plants, which provide shade, shelter and food for these native fish. However, this restored habitat is of no use if the fish cannot access it.
Native fish are great climbers, but they need eddies and variable substrate to travel up fast flows. Today, large tracts of native habitat are inaccessible due to weirs, culverts, and dams that are too long, fast-flowing, or too steep for native fish to swim up.
Many of these barriers can be easily fixed by novel and low-cost solutions such as mussel rope, “baffles”, and “flexi-ramps” in culverts. These simple technologies break up fast-flowing streams, give fish grippy surfaces to climb up waterfalls, and provide fish with rest spots along culverts so they can catch their breath.
Wai Kōkopu and the Bay of Plenty Regional Council are now beginning to map these barriers to fish passage throughout the catchment and assess where remediation is most urgently required. Once we have mapped these barriers, we will begin utilising these solutions to provide upstream access once again.
Next time you’re out on the farm, have a look at your culverts and drains, and ask yourself if there are any barriers to native fish – if so, get in touch - we would love to help you fix it.