Native freshwater fish

In this interactive, click on the name of the fish or group of fish to learn more.

To learn more about some of the terminology in this interactive, refer to Freshwater and freshwater fish – key terms.

Transcript

Eels

Three eel species are present in New Zealand – the shortfin, longfin and Australian longfin (Anguilla reinhardtii) or spotted eel, thought to have arrived of its own accord as recently as 25 years ago.

Eels (tuna) are such an important resource for Māori that, in the past, battles were fought over them. Tuna were caught using woven pots (hīnaki), stream fences (pā tuna), spears (matarau), nets (kōrapa), baited lines (toi), ditches (koumu) or bare hands. Māori have over 100 local names for the three species of eels in New Zealand.

Like some galaxiids, eels also make the arduous journey between the sea and freshwater to complete their life cycle.

Updated science: In this video Erina explains that the leptocephali – eel larvae – 'float' back upstream on the current. Current scientific belief is now that the larvae are not passive drifters but have some swimming ability to get them where they need to go. The nature of science is such, that we are often having to reevaluate our ideas and knowledge.

Transcript

Erina Watene-Rawiri

Taonga species are species that are precious to Māori.

Eels are a taonga species, so Māori have relied on eels for generations.

Eels have quite a complex life cycle. They spend part of their life in the ocean and part in freshwater, so if we start with the adults, they’ll be hanging out in the streams and lakes. And then when they’re ready to go out and spawn, they head down stream en masse and out to the ocean. They swim for a couple of thousand miles out towards Tonga where they spawn, at quite a depth.

The eggs then rise to the surface and hatch, and you have these little tiny eel larvae, which are see-through and they’re leaf-shaped – they’re called leptocephali. The leptocephali float back to New Zealand on the ocean currents, and just before they head back up into the rivers, they metamorphose into what we call glass eels. Glass eels are tiny see-through baby eels, and they swim up the river, and as they continue on up the river, they change colour, they go black. And they turn into what we call elvers, and elvers are just pretty much miniature versions of adult eels. And they stay in freshwater from anywhere between 20 to 60 to 100 years before they become adults, and then they head back out to sea and spawn again. The adults, when they spawn, they die – only the babies come back.

Acknowledgement: © University of Waikato. Please refer to video credits for acknowledgements.

Longfin eel

The longfin eel (Anguilla dieffenbachii) inhabits all types of water from tiny streams to the largest rivers, coastal and inland lakes, brackish (semi-salty) estuaries and lagoons.

The longfin can grow to 2 m long and live for over 100 years! The life cycle remains something of a mystery. The eels breed only once at the end of their life cycle. In autumn, adult eels leave the rivers and streams and head for the ocean. Scientists think the spawning grounds may be close to Tonga, but their spawning has not ever been recorded.

Considered a threatened species, longfin catch limits have recently been reduced and a maximum size limit applied to protect the large mature females.

The longfin eel has yet to be assessed for the IUCN Red List, but the New Zealand Threat Classification System lists it as ‘at risk – declining’.

Acknowledgement: Public domain

Dwarf galaxias

The endangered dwarf galaxias (Galaxias divergens) is found in riffley marginal shallows of larger rivers and in gravel/cobble riffles of smaller streams, mostly in foothill catchments. It requires good riparian cover, streamside shade and logs and/or boulders instream. Its most common food is the aquatic larvae of mayflies and midges.

In the North Island, the dwarf galaxias occurs in the headwaters of the Waihou River near Putaruru, at a few sites in the Rangitaiki River near Galatea in Hawke’s Bay and in the Wellington region. In the South Island, it occurs in Marlborough and Nelson and on the West Coast as far south as the Hokitika River.

Acknowledgement: Bob McDowall

Bullies

The seven species of freshwater bullies in New Zealand, which belong to the Eleotridae family, are the:

• Tarndale bully (Gobiomorphus alpinus)
• Cran’s bully (Gobiomorphus basalis)
• upland bully (Gobiomorphus breviceps)
• common bully (Gobiomorphus cotidianus)
• giant bully (Gobiomorphus gobioides)
• bluegill bully (Gobiomorphus hubbsi)
• redfin bully (Gobiomorphus huttoni).

A number of the species are difficult to tell apart, and scientists rely on microscopes.

Bullies are found in a range of habitats including streams, rivers and lakes. Of the seven species, three are strictly diadromous (bluegill, redfin and giant bullies), while three are non-diadromous (Cran’s, upland and Tarndale bullies). The common bully can be either.

Bullies are well camouflaged against sand and rocks but can be seen darting in the shallows during the day or night.

Unlike the galaxiids, they have coped well with humans, remaining fairly widespread and abundant, with only one species regarded as threatened. On the New Zealand Threat Classification System, the Tarndale bully is ranked ‘at risk – naturally uncommon’ because it is found only in a few small subalpine tarns in the headwaters of the Clarence and Wairau Rivers in the Marlborough region. The total area these fish occupy is calculated at 0.59 km². However, it remains listed as ‘least concern’ on the IUCN Red List, as the extreme isolation of its location is seen as a positive for its protection.

Acknowledgement: Tarndale bully images courtesy of Stella McQueen

Shortjaw kōkopu

The shortjaw kōkopu (Galaxias postvectis) is unique to New Zealand. It is rare, secretive and seldom seen. It has an undercut jaw, which scientists think is adapted to scrape aquatic insects from rocks.

It is only found in streams with large boulders within native forests. Not being adapted to a variety of different habitats is one reason it is so rare.

All kōkopu lay their eggs on leaf litter and plants above streams during high flows. The hatched larvae then float out to sea where they live and grow over winter, migrating back upstream as whitebait in spring. However, all whitebait species can ‘lake-lock’ and carry out their entire life cycle in freshwater – this is termed lacustrine. To date only, one known lacustrine shortjaw kōkopu population has been found (in Mangatawhiri Reservoir), but species such as giant kōkopu, banded kōkopu and kōaro have a multitude of lacustrine populations nationwide.

Acknowledgement: Stella McQueen, Creative Commons 4.0

Common bully

The common bully (Gobiomorphus cotidianus) is everywhere in New Zealand. It lives in rivers and streams near the coast and land-locked lakes. In rivers and streams, it mainly inhabits still or slow-flowing water. It is an important prey species for other fish, including eels.

Eggs are laid on the undersides of hard substrates (wood, rock) in lakes and rivers, and the developing eggs are defended by the male.

Acknowledgement: Mike Dickinson, CC BY 4.0, sourced from iNaturalistNZ

Redfin bully

The redfin bully (Gobiomorphus huttoni) is strictly diadromous and does not establish in land-locked waterways like lakes. It tends to live near the coast, even though it is a very good climber (populations above 5-metre high waterfalls have been recorded).

Spawning takes place in freshwater, and after hatching, the larvae are swept out to sea. The juveniles enter freshwater in the spring and reach maturity about 2 years later.

Redfin bullies occur mainly in the runs and riffles of small bouldery streams, and their principal food is mayfly, caddisfly and chironomid larvae. Because of their dependence on this habitat, they are more sensitive to the effects of siltation in streams than other fish species.

Acknowledgement: Stella McQueen, Creative Commons 4.0

Banded kōkopu

The banded kōkopu (Galaxias fasciatus) lives in pools with good cover such as overhanging banks, logs and boulders. It is usually found in pools or under undercut banks. Like the giant kōkopu, it is sometimes referred to as the Māori trout or native trout.

These fish prefer stream temperatures of 12–18°C and are particularly sensitive to pollutants such as ammonia, which occurs in livestock waste and poorly treated wastewater.

Banded kōkopu lay their eggs on leaf litter and plants above streams during high flows. The hatched larvae then float out to sea where they live and grow over winter, migrating back upstream as whitebait in spring. However, some populations can ‘lake-lock’ and carry out their entire life cycle in freshwater – this is termed lacustrine. Banded kōkopu have a multitude of lacustrine populations nationwide.

Acknowledgement: Stella McQueen

Torrentfish

The torrentfish (Cheimarrichthys fosteri) is the only species in the family Cheimarrichthyidae in the world!

It is found in fast-flowing rivers with a gravel substrate, often occupying the fastest-flowing areas particularly in riffles, rapids and torrents. It spends little time actively swimming against the rapids, living instead amongst and beneath loose gravels and cobbles. It emerges from the rapids at night to feed.

The torrentfish is well adapted to this habitat, with a flattened head and large pectoral fins to help anchor itself on the riverbed, while the raised eyes and ventral mouth are probably adaptations for feeding in this habitat.

Like many of New Zealand’s freshwater fish, the torrentfish undertakes migrations between the sea and freshwater as part of its life cycle. Although spawning sites have never been located, it is believed that male and female torrentfish migrate within freshwater habitats to spawn, with larvae moving out to sea and the juveniles returning to freshwater.

The torrentfish appears on the IUCN Red List with a conservation classification of ‘vulnerable’. This is because it requires a specialised habitat with cool, highly oxygenated, fast-flowing water, and so it is threatened by water being taken for irrigation, water pollution and climate change. River sedimentation is also a threat, as it needs to live amongst loose gravels and is less common in waterways with compacted substrate.

Acknowledgement: Stella McQueen, Creative Commons 4.0

Mudfish

There five species of mudfish in New Zealand are the:

• Canterbury mudfish (Neochanna burrowsius)
• brown mudfish (Neochanna apoda)
• black mudfish (Neochanna diversus)
• Northland mudfish (Neochanna heleios)
• Chatham mudfish (Neochanna rekohua).

Despite the name, mudfish require clean water and are a good indicator of a healthy environment. They are found in swampy lowland habitats such as wetlands, pakihi, pools in swamp forests and slow-flowing streams and drains. The Chatham mudfish is an exception, as it lives around the margins of peat lakes.

With 80–90% of New Zealand’s wetlands having been drained or filled, habitat loss is the key reason for the decline of these species. Mudfish have a bizarre ability to live out of water in tree root hollows and damp leaf litter for weeks at a time during dry periods. They are able to do this by wriggling their cigar-shaped bodies into tiny crevices, where they semi-hibernate (aestivate) by ‘breathing’ through their moist skin. This means that they can survive in seasonally dry waterways, drains, pools and swamps.

All five species of mudfish are considered highly threatened due to habitat loss. All appear on the conservation classification IUCN Red List, with the Canterbury and Northland mudfish listed as ‘critically endangered’.

Acknowledgement: Department of Conservation, Te Papa Atawhai, Creative Commons 4.0

Shortfin eel

The shortfin eel (Anguilla australis) is not unique to New Zealand. It also occurs throughout the South Pacific in Australia, New Caledonia, Norfolk Island, Lord Howe Island and perhaps Fiji. Generally, it lives at low elevations and does not go as far up river and inland as the longfin eel. It prefers warmer brackish water, coastal lakes and lowland lakes.

It is carnivorous, eating crustaceans, fish, frogs and even small birds.

It migrates from freshwater to the ocean to spawn and die. The returning juveniles are good climbers.

Shortfin eels are our most tolerant native fish species. They survive environmental hazards like high water temperatures or low dissolved oxygen concentrations. That means they can live in habitats where other species cannot survive.

The shortfin eel can be differentiated from the longfin eel by the length of its dorsal fin. It is also somewhat smaller as an adult.

Acknowledgement: NIWA, Taihoro Nukurangi

Giant kōkopu

The giant kōkopu (Galaxias argenteus) is sometimes referred to as the Māori trout or native trout and is the largest of all the galaxiids.

Although the giant kōkopu possesses some climbing ability, it is generally found close to the sea. It inhabits wetlands, lakes and forest streams and relies on good bush surrounds. It is usually found in pools or under undercut banks within the stream.

It is slow growing and can live for more than 20 years.

Giant kōkopu, like all kōkopu and kōaro, lay their eggs on marginal vegetation above streams during high flows. The hatched larvae then float out to sea where they live and grow over winter, migrating back upstream as whitebait in spring. However, some populations can ‘lake-lock’ and carry out their entire life cycle in freshwater – this is termed lacustrine. Giant kōkopu have a multitude of lacustrine populations nationwide.

Acknowledgement: Stella McQueen

Giant bully

The life cycle of the giant bully (Gobiomorphus gobioides) remains somewhat of a mystery. Adults appear to prefer slow-flowing coastal habitats and are never found more than a few kilometres inland – it is possible that they may spend a long period in estuaries before moving into freshwater. Giant bullies are almost always found beneath cover, and emerge at night to feed.

The larvae are thought to have a marine phase, but no juvenile giant bullies have ever been positively identified.

The giant bully has been found in most regions in New Zealand. To date, there have been no studies of this fish so there is little known about it.

Acknowledgement: Grahame, CC BY-NC-ND 4.0, sourced from iNaturalistNZ

Kōaro

The kōaro (Galaxias brevipinnis) is an excellent climber with specially adapted broad fins that have a grippy texture underneath. It is capable of climbing vertical waterfalls. This solitary, nocturnal fish is usually found in fast-flowing, cool, tussock or forest streams.

Living for 15 years or more, the kōaro travels as far as 400 km inland and can climb as high as 1,300 m.

Like the kōkopu, the kōaro can lay its eggs amongst leaf litter in forested streams during high flows but is also known to lay eggs amongst cobbly substrate within the stream. The hatched larvae then float out to sea where they live and grow over winter, migrating back upstream as whitebait in spring. However, some kōaro can ‘lake-lock’ and carry out their entire life cycle in freshwater – this is termed lacustrine. Kōaro have a multitude of lacustrine populations nationwide.

Acknowledgement: Stella McQueen

Lamprey

The lamprey (Geotria australis) belongs to is a primitive order of jawless fish (Petromyzontiformes). The adults are good climbers and can scale waterfalls, but because of habitat loss and dams blocking their migrations, most populations now occur at lower altitudes (less than 400 m) closer to the coast.

Lamprey juveniles (ammocoetes) live in burrows in silty river edges. As ammocoetes, lamprey are blind and browny-black in colour. Once they reach 100–120 mm (after 3–5 years’ growth), they metamorphose into the adult form, which contains eyes and a vibrant blue colouration. This stage is termed macropthalmia, and these fish will migrate out to sea to feed parasitically on fish and whales.

Lampreys are anadromous – this means they migrate up rivers from the ocean to spawn. The eggs hatch in freshwater where juveniles reside for up to 4 years before heading out to the open ocean. Here, they attach onto the gills and flesh of other fish and marine mammals and live as parasites. They use their specially adapted mouth – a roundish sucker, armed within by series of rasping teeth, with sharper and stronger ones on the tongue – to feed on the host animal’s blood.

Before reaching sexual maturity, the lamprey returns to freshwater to breed and can use its circular sucker to latch onto and surmount obstacles such as rapids and small falls.

The returning adult lamprey spends up to 18 months inland, maturing sexually before spawning. Both sexes will survive spawning for over 3 months before dying. Scientists discovered the first Geotria australis spawning sites in the southern hemisphere on Canterbury's Banks Peninsula.

The adults do not feed in freshwater – so other freshwater fish and people wading in streams will not be preyed on!

Lamprey – also called kanakana or piharau – are a taonga species and were considered a delicacy by Māori.

Watch a lamprey using its sucker mouth to climb a wall in this video.

Acknowledgement: Peter Anderson, Department of Conservation Te Papa Atawhai, Creative Commons 4.0

Grey mullet

The grey mullet (Mugil cephalus) is one of two of the Mugilidae family found in New Zealand – the other is the yellow-eyed mullet.

Grey mullet have a worldwide distribution, and New Zealand is at the southern limit of their range. They are mainly found in the North Island and only in the Cook Strait area during the summer months. They live in harbours, mangrove swamps and estuaries. Although primarily a marine species, grey mullet will penetrate considerable distances upstream. In the Waikato River, they are found as far inland as Karapiro Dam and travel up the neighbouring Waipa River to Te Kuiti. However, they must return to the sea to spawn.

Grey mullet feed on detritus and plant material that they suck from the substrate. They are also known to feed by grazing the surfaces of aquatic plants.

Acknowledgement: Izuzuki, Creative Commons 3.0

Inanga

Inanga (Galaxias maculatus) are the most common of the five whitebait species. They are usually found in lowland freshwater habitats including coastal creeks and streams, rivers, lagoons, lakes, estuaries and wetlands. Inanga are often found swimming in shoals. They are commonly seen during the daytime, often feeding on tiny insects.

The life cycle of the inanga is the best understood of the five species of whitebait. Inanga migrate to estuaries to spawn on autumn/winter king tides. They lay their eggs within the vegetation at the estuary edges. Their eggs stick to damp grasses, rushes, sedges and flax and hatch around 4 weeks later on the next set of high tides. Floods and ebbing tides induce the larvae to hatch before being carried by the current out to sea where they spend 4–6 months feeding on microscopic plankton. They then return to freshwater between early spring and early summer, swimming upstream together as whitebait.

However, some inanga can ‘lake-lock’ and carry out their entire life cycle in freshwater – this is termed lacustrine.

They don’t tend to travel long distances inland as they have difficulty swimming through swift-flowing rapids and cannot climb past waterfalls.

Acknowledgement: Stella McQueen

Smelt

There are two species of the Retropinnidae family found in New Zealand – the common smelt (Retropinna retropinna) and Stokells smelt (Stokellia anisodon). Stokells smelt are only found on the east coast of the South Island, around the river mouths and estuaries of the big braided rivers.

Smelt are a shoaling species, which means they swim in schools near the water surface rather than resting or hiding on the substrate. They are often seen out in the open in streams and lakes as they feed on drifting food organisms.

The common smelt is widespread throughout New Zealand. It lives in flowing and still water, and there are both diadromous and non-diadromous populations here.

Although they are not a climbing species, smelt are good swimmers and will penetrate well inland in river systems that are not too steep.

Smelt are very sensitive to pollutants like ammonia and stressors like high water temperature. Smelt are therefore an appropriate native species for establishing guidelines for New Zealand waterways, and usually their presence indicates that the water quality is suitable for most other fish.

In rivers, juveniles are often captured by whitebaiters as they migrate upstream and mix with the whitebait (galaxiids). In the Waikato catchment, they are referred to as “number two whitebait” and are actively fished for.

Acknowledgement: Department of Conservation Te Papa Atawhai, Creative Commons 4.0

Black flounder

The black flounder (Rhombosolea retiaria) is the only member of the flatfish family, or Pleuronectidae, that is a truly freshwater species. The black flounder is unique to New Zealand and is the only freshwater flounder (of the right-eyed family) in the whole world.

They are primarily a coastal species, but also live in estuaries, lowland lakes and the lower reaches of rivers. They can penetrate well inland if the river gradient is not too steep. They occupy a variety of substrates, from silty to cobbly bottoms, and can live in rivers and streams of different flow rates.

The adults are predatory carnivores – camouflaging themselves on the bottom then ambushing small fish. They are also known to feed on whitebait during the spring migration. Little is known about the life cycle of the black flounder except that adults migrate to sea in winter, where they likely spawn.

Acknowledgement: Stella McQueen, Creative Commons 4.0

Galaxiids

New Zealand’s largest group of freshwater fish are galaxiids from the Galaxiidae family. The 30 species include īnanga, kōkopu, kōaro and mudfish.

The name ‘galaxiid’ refers to the clusters or ‘galaxies’ of golden or silvery star-like patterns on their scaleless bodies – perfect camouflage in the dappled light of the small forest streams they tend to favour. They are also found in swamps, drains and larger waterways. Most of the galaxiids are great climbers, able to scale waterfalls helped by ridges on their fins.

Galaxiids have sensors on their head and body – the lateral line – this is part of the non-visual sensory systems of all fish. However, kōkopu species have evolved to use the sensors on the head to detect when and where something hits the water, enabling them to feed on insects that fall from overhanging plants at night.

The galaxiid diet is predominantly invertebrates – both aquatic species, including a number of macroinvertebrates, and those that fall into the water.

Many of our native galaxiids are threatened, with nearly half of them appearing on the IUCN Red List. The tiny lowland longjaw galaxias (Galaxias cobitinis) is New Zealand’s rarest native fish and is listed as ‘critically endangered’.

Acknowledgement: Upland longjaw galaxias (Galaxias prognathus), Simon Elkington, Department of Conservation. Creative Commons 4.0

Whitebait

Whitebait are five species of diadromous, migratory galaxiids. Four of the five whitebait species are threatened due to habitat loss, predation by trout, whitebaiting and obstacles in waterways that hinder their migration, such as culverts. Only the banded kōkopu is not threatened.

Except for īnanga, our whitebait species are nocturnal. The eggs of the whitebait species stay out of water for several weeks and need good plant cover to keep moist.

Young common smelt (Retropinna retropinna) are also sometimes called whitebait.

Transcript

Cheri van Schravendijk-Goodman

Whitebait is a sort of a collective term for those lovely sparkly fish that we collect and we put in our omelettes and they taste really good. But there’s actually five different galaxiid species in there. We have the giant kōkopu, the banded kōkopu, shortjaw kōkopu, kōaro and then the most common one which is the īnanga. Our people at Te Pūaha also talk about whitebait including at least one other species – they call it the number two whitebait – and that’s the common smelt, or our people call it pōrohe.

The īnanga is the most common one, and they tend to like spawning in the more estuarine, so the slightly salty water. They lay their eggs in the grassy verges, so literally a big king tide comes up the river from the ocean and lifts the water level, and the fish use that water level to get into the grassy verges on the edge, and they lay their eggs in there. And then the water level will drop again, and those eggs are sort of left there in these nice moist environments. And then the next king tide comes in, lifts the water surface up again and washes these larvae out to sea.

And so they are out there somewhere in the 200 nautical mile zone area, and there are question marks as to what is actually happening to them out there.

The other fish – the kōkopu and the kōaro – again, there’s question marks about their spawning habitat, so a lot’s known about īnanga because they’re the most obvious to see and there’s heaps of them, but the kōkopu and kōaro tend to like the rocky, densely overhanging streams and tributaries.

We’re working with NIWA to train some of our people who live in those tributary catchment areas, giving them the skills to go out and start monitoring and try find out more information about the kōkopu and kōaro.

Acknowledgement: © University of Waikato. Please refer to video credits for acknowledgements.