North Shore Times (New Zealand)
City’s whitebait are under threat
The Kiwi whitebait fritter, is under threat due to a flow-on effect from urban stream pollution and depletion.
Whitebait is the generic term for kokopu, an endemic fish that lives in New Zealand streams. Auckland is home to five species of kokopu, four of which are rare or endangered.
Northcote College science teacher Kit Hustler has been studying the kokopu in Le Roys Bush since 2009. Like kiwi, tuatara and fantails, kokopu are native animals; yet, they are the only endemic species to not need a permit to study them, Hustler says.
Kokopu have several unique features: they can launch themselves out of the water for food, juveniles can clamber up waterfalls, and eggs develop out of the fresh water on the banks.
Eggs wash into the sea to hatch, then the juveniles find their way back into streams via a chemical ‘‘signal’’ released by the adults, which basically says ‘‘there’s good habitat here to live in’’, he says.
It’s the babies in the sea that are caught and made into fritters. ‘‘No streams, no adults, no babies, no fritters. It’s very simple,’’ he says.
Like real Kiwi kids, kokopu are caught by using marmite bait in minnow fish traps. Hustler records and photographs the individuals, before returning them to the stream.
Suburban streams have been ‘‘hammered’’ by a number of events,’’ Hustler said. Sewerage overflows, sediment from development, building of walkways have contributed to a significant decline in the population. ‘‘I used to catch, roughly, 20 baby fish a year, now its about three,’’ Hustler says.
Auckland Council’s senior regional biodiversity advisor Matthew Bloxham says Auckland’s streams vary from awful to ‘‘glorified gutters’’. However, Bloxham says better understanding will lead to a better future.
Our team works with engineers to protect streams from development, as well as advise Auckland Council and members of the public on stream health, he says.
‘‘By ripping up the concrete, rehabilitating the streams and bartering against stormwater inflow we can claw back streams to their original state, as best as possible.’’