inanga

Native Fishes of the Whanganui

A native grayling recently rediscovered in the collection, caught in the 19th century.

A native grayling recently rediscovered in the collection

New Zealand is famous for its extinct birds, but not many people know we have an extinct fish. The native grayling or upokororo (Prototroctes oxyrhynchus) was found in many rivers and streams, including the Whanganui basin. The size of a small trout, it was good eating and extensively fished by Māori and pākehā. By 1900 it was rare, and it disappeared in the 1920s.

Remarkably, we recently came across a native grayling in our collection. Some time in the 19th century it was skinned, stuffed with cotton wool, and mounted on a board (originally painted blue, from the traces of blue paint on the fish’s back). At nearly 30 cm long, it’s one of the largest specimens known.

It’s hard to imagine what the Whanganui River was like at the time that grayling was stuffed and mounted. The first pākehā settlers described the banks as steep and lined with piles of sunken logs. When this wood was dug out for building, the banks eroded back a chain (about 20 m) on both sides. A century ago, a newspaper accounts tells us, the Whanganui was clear enough for someone to find a wedding ring on the river bed that had been dropped from the town bridge; imagine trying to find anything dropped into the river today! There were numerous side streams, even in the middle of town, that have since been covered over and culverted.

The Giant kokopu (Galaxias argenteus)

The Giant kokopu (Galaxias argenteus)

The river and side streams would have teemed with native fishes. Not just eels, but īnanga (the main whitebait species) and many different kinds of kokopu. The largest was the giant kokopu, growing over 40 cm long and weighing up to 2 kg. We only know that giant kokopu lived here because the museum has one, preserved in alcohol, caught at Kaitoke in 1948. Who knows how much longer they hung on in the area before being wiped out by agriculture and overfishing?

The kokopu pool near Karaka Street

The kokopu pool near Karaka Street

Even today, you can still find native fishes in some of the remaining urban streams in Whanganui. Īnanga and eels live in the creek running behind Aramoho School, and rare freshwater mussels are still surviving in the Matarawa Stream that flows through Kowhai Park. The swampy wetland behind the houses in Karaka St drains into a small stream, which was originally created as a drainage ditch but turns out to have the largest population of banded kokopu (Galaxias fasciatus) we’ve yet found in the Whanganui area.

The banded kokopu (Galaxias fasciatus)

The banded kokopu (Galaxias fasciatus)

As part of River Week, local fish expert Stella McQueen and I ran a night-time fish-spotting expedition to Karaka Wetland. Most native fishes are nocturnal, so can only be caught with headlamps and nets. We caught, measured and photographed banded kokopu (some up to 24 cm) long and released them into the stream again, except for two, which are on display in our aquarium in the Museum atrium.

Raising awareness of native fishes is part of our job; these are taonga, some of them threatened or endangered, literally living in our backyards. They’re incredibly vulnerable: vandals, eel fishers, or someone thoughtlessly dumping a drum of paint thinner could wipe out a streamful of fishes that have hung on right through Māori and European settlement, from a time when the Whanganui and its streams only flowed through swamp and forest.

Dr Mike Dickison is Curator of Natural History at the Whanganui Regional Museum.

One Fish, Two fish … Five Fish, New Fish!

Five whitebait may not seem like much of a catch, but the Museum was very pleased to get them.

Horizons Regional Council looking for fishes in the Tutaeika. Photo: Damien Wood.

Horizons Regional Council looking for fishes in the Tutaeika. Photo: Damien Wood.

Perhaps a proper whitebait net would have helped, instead of two aquarium dip nets, but we were trying to catch adult whitebait, or īnanga, for the Museum’s new aquarium. The word “whitebait” actually refers to the juveniles of not one but five different species of native fish; young īnanga are the most common of those five. Adult īnanga are attractive little fishes about the size of your finger. Their scientific name Galaxias maculatus (maculatus means spotted) describes their leopard-like spots, and they have an iridescent greenish stripe. In the aquarium they hover in the filter current in a tidy shoal.

Native fishes are mostly nocturnal, so at 11 pm on Saturday night the Curator of Natural History was wading up the muddy Tutaeika Stream in Aramoho, being eaten by mosquitoes, peering into the water with a powerful head lamp. The Tutaeika has a history with local hapu as a food-gathering site, but in the daytime it doesn’t look like much: it emerges from a culvert, flows like a drainage ditch through open fields with no shelter, and runs for a short distance behind backyards and Aramoho School, fringed with weeds, before emptying into the Whanganui River. But at night I counted at least four species of fish—īnanga, a middle-sized eel, banded kokopu, and common bully. A recent fish survey by Horizons found koura (freshwater crayfish) there too, and the introduced pest fish Gambusia—impressive diversity for a neglected suburban stream.

Adult īnanga ('Galaxias maculatus') Credit: Whanganui Regional Museum

Adult īnanga (‘Galaxias maculatus’) Credit: Whanganui Regional Museum

Each year, the whitebait that escape the nets head upriver to sheltered streams to feed and grow over summer. By autumn, after eating voraciously, īnanga are the size of the adults in our aquarium, and head downriver to spawn. They lay eggs around the base of grass and reeds in the estuary, and most then die. The young īnanga head out to sea for the winter after they hatch, and return in spring as whitebait. So most īnanga live for only a year—the ones in our aquarium won’t be spawning, so will live for two or three years.

The Whanganui Regional Museum’s new native fish aquarium. Credit: Whanganui Regional Museum

The Whanganui Regional Museum’s new native fish aquarium. Credit: Whanganui Regional Museum

We set up our aquarium to mimic the streams around suburban Whanganui: the fish are natives, but the lush greenery is all invasive weeds, plants originally imported by fishkeeping hobbyists and now choking our waterways. It’s sitting in the museum atrium, and seems popular—green swaying plants and darting fish are almost hypnotic.

Part of the job of a museum is to document and preserve the natural history of its area, so in 100 years locals and scientists can see what’s been lost or gained. Our job is also to raise awareness of treasures that would otherwise be overlooked; treasures that might be in your backyard, especially if you live in Aramoho.

Mike Dickison is the Curator of Natural History at Whanganui Regional Museum.