NZ Freshwater Species

There are well over 600 freshwater species in New Zealand; these have to be one of the most important factors in a functioning wetland ecosystem, here's why:

  • A range of freshwater species in NZ feed on insects, algae, or debris and then get eaten by larger predators like Longfin eels, moving energy through the food chain.

  • Top predators like eels can also help with population control of other species, preventing any one species from taking over the ecosystem.

  • Sensitive species like whitebait can be an indication of water/stream health and quality.

Now here's some freshwater species that could be in your local lakes and streams!

 

Shortfin eels

  • Shortfin eel are not native to NZ, but they very closely resemble the longfin eel. These eels are often narrower and much smaller than Longfins.​

  • Shortfin eels are found much of the same habitat as Longfins, they too can breathe in saltwater as well as fresh.​

  • Shortfin's have a similar diet of aquatic insects,snails, crustaceans and when larger they also eat other fish.​

  • Shortfin's habitat is basically the same as that of a Longfin except they area little bit more resistant to harsher or more extreme temperatures or conditions.​

  • Shortfin are much lighter in colour than Longfins with some having greenish-brown or olive-greenbacks and a light silvery underbelly.​

  • Shortfin eels are often considered scavengers meaning they will clean up any decaying animals or other dead aquatic life keeping the water clean and free of diseases/unwanted bacteria. 

Longfin eels

  • An incredible fact about Longfin eels is that they migrate thousands of kilometres from their home lakes/streams into the deep south Pacific ocean near Tonga to spawn. This journey, however, is one way. After Longfins spawn they die. Their fertilised eggs hatch into larvae and make the journey back to NZ and by the tides and currents of the ocean they are able to return home. But it's not over yet. The larvae turn into young elvers and navigate the maze of streams and rivers, returning to their parent's home waterway.

  • Longfin eel are native to NZ and have the unique ability to breathe in salt and freshwater.

  • They can even breathe through their skin meaning they can stay out of the water for up to two days.​

  •  They can be identified by their dark brown or grey/black colour or the longer tail fins and the tail fins themselves being closer up the body to the pectoral fin.​ 

  • Longfin can be found in a variety of water types and habitats like lakes, ponds, rivers and streams usually well inland from the coast.​

  • Longfin are rarer than the typical Shortfin and are much larger.​

  • Longfin will eat insect larvae, worms, water snails and when they get big, they can even eat fish and small birds like ducklings.​

  • Longfin eels are apex predators in many lakes/streams helping keep the population down of other small invasive fish species.​

  • Despite this juvenile eels (elvers) and eggs provide food for other small aquatic life keeping themselves from dominating.

 

 

 

 

 

Koura

  • The koura is a freshwater crayfish found only in New Zealand. It can be found in rivers, streams, and lakes throughout the country.​

  • Koura are relatively small, usually growing to about 10–15 cm in length, though some can grow larger. They have a dark brown or greenish colour and a hard exoskeleton, which they moult as they grow.​​​

  • They prefer cool, clean, and well-oxygenated freshwater habitats. The koura is typically found hiding under rocks or in burrows at the bottom of streams and lakes, where it is protected from predators.​

  • Koura are omnivores. Their diet includes aquatic plants, small invertebrates, and decaying organic matter. They are opportunistic feeders and will scavenge when they can.​

  • While koura are not currently endangered, they face threats from habitat destruction, pollution, and invasive species.Conservation efforts focus on maintaining clean, natural freshwater habitats for them to thrive.​

  • Koura's diet controls algae from taking over and overwhelming other wildlife.​

  • Their habitat disturbs sediment when they borrow into their whole oxygenating the water.

 

 

 

 

Kakahi Freshwater  Mussel

  • Kakahi mussels are an endangered freshwater musselspecies native to NZ.​

  • They live in rivers, lakes, and streams across the countryoften buried in the sand or sediment.​​​

  • Kakahi are natural filter feeders. They suck in water, trap things like algae, bacteria, and organic debris, and then excrete the clean water, like how a tree converted co2 in oxygen.​

  • This helps improve water clarity and quality, which benefits other aquatic life like fish and plants.​

  • Kakahi live buried in the sand/sediment helping to stabolize the lake/riverbed.

 

 

 

 

 

Inanga-Whitebait

  • Inanga are a small white or translucent fish of about 80-110mm. ​

  • They are found in New Zealand's coastal rivers, streamed and lakes.​

  • Whitebait are also a great food source for predators higher in the food chain because of their abundance.​​

  • They are extremely sensitive to water pollution, habitat degradation, and barriers like culverts and dams.​

  • Because of this their presence (or absence) could help determine the health of your waterway.

  • They also lay their eggs on banks fertilising the roots of riparian plantings.

 

 

 

 

 

  • Koaro usually grow to about 16-18 centimetres and usually live about 12 years.
  • Koaro are not officially endangered yet but their numbers have been decreasing because of invasive species like trout and smelt taking over or even eating them.
  • They themselves are opportunistic feeders liking things like mayfly and caddisfly larvae.

 

 

 

 

 

Koaro

  • Koaro are are a small fish species endemic to NZ and Australia (and Tasmania), as well as the Chatham and Campbell islands.

  • It's scientific name is Galaxias Brevipinnis, but in Australia it is often called the 'Climbing Galaxias' due to it's ability to climb up near vertical surfaces like, wet rocks, waterfalls, and even dam sluices.

  • They are found in the North Island as well as the more northern parts of the South Island.

  • Its not uncommon to for juvenile Giant Kokapu to be part of the average kiwi whitebait-ers catch in NZ.

  • Adult Giant Kokapu, however, reside in lowland streams, lakes, and wetland areas.

  • They have few predators, some include large birds and eels.
  • Despite this, the species is declared to be, 'at risk-declining' due to not just predator but migration barriers like culverts  and wetland degradation throughout the country.

 

 

 

 

 

Giant Kokapu

  • Giant Kokapu are the largest of the whitebait species.

  • They can reach up 58 centimetres long and weigh up to 2 kilograms although most are about 30-40 centimetres in length.

  • They have a stocky body and a large mouth, golden speckles and splotches over a dark olive background-not unlike a leopard.

              Banded Kokapu                                        Shortjaw Kokapu

  • There are two other different types of Kokapu in NZ: Banded and Shortjaw Kokapu.

  • They are very similar though, their main difference being appearance and habitat.

  • Banded Kokapu have bands of lighter brown around there body-almost stripes-and tend to be much lighter in colour. Their young are also part of the whitebait run.

  • Shortjaw Kokapu however, which are almost a pale muddy brown colour, have a much shorter bottom jaw meaning their upper one extends well past the lower one. They are often found in steep boulder-filled forest streams. This incredible species though are extremely rare and have been declared nationally threatened.

 

 

 

 

 

Common Bully

  • A greyish to brown body with darker blotches and a pale underside.

  • Males get more colourful during breeding, often showing a bluish tint.

  • Usually around 6–9 cm long

  • Found in almost all freshwater habitats like rivers, lakes, streams, ponds and even brackish estuaries. They one of NZ's most widespread and common freshwater species, hence the name.

  • they will eat small invertebrates like insect larvae and crustaceans.

  • They also provide as a valuable and plentiful food for larger fish and birds due to their numbers.

  • They also help balance out invertebrate populations.

 

 

 

 

 

Crans Bully

  • Similar to common bullies but with fewer, darker blotches and a more compact body.

  • Often has a dark stripe from the eye to the tail base.

  • Around 6–8 cm long.

  • Although they have a hint of red at the tip of their dorsal and secondary dorsal fins don't get them confused with Redfin Bullies witch have much more vibrant reds on all of their fins. When you see a Redfin Bully you will know it, trust me.

  • Prefers clear, stony streams in the North Island (especially eastern regions).

  • Needs clean, well-oxygenated water — so it’s a good indicator of water quality.

  • Feeds on aquatic insects and tiny crustaceans.

  • Keeps algae blooms in check by eating grazers.

 

 

 

Redfin Bully

 

  • Males develop distinct red-orange stripes on their fins when breeding.

  • Females are more plain brown.

  • Around 6–9 cm long.

  • Prefers clean, swiftly flowing streams with gravel, cobble, or stony bottoms.

  • Also diadromou's young spend part of life at sea.

  • Eats aquatic insects, mainly larvae.

  • A key prey species for native eels and larger fish.

 

 

 

 

Bluegill Bully

 

  • Males have bright blue cheeks and gill covers — very distinctive.

  • Smallest of the bullies, usually 4–7 cm long.

  • Females are duller brown-grey.

  • Lives in fast-flowing, rocky streams, often close to the sea.

  • Diadromous — adults live in freshwater, but larvae drift to sea before returning.

  • Feeds on mayfly and caddisfly larvae found among rocks.

  • Their presence shows a healthy, unpolluted stream.


 

 

 

 

 

Pea Clams (Sphaerium novaezelandiae)

  • Sphaerium novaezelandiae, commonly known as the New Zealand pea mussel, is a tiny native freshwater clam found in ponds, lakes, and slow-moving streams throughout New Zealand.

  • They are usually 6–12 mm wide, with smooth, oval shells that are pale brown to grey in colour.

  • Found in lakes, rivers, streams, and wetlands — often buried in soft sandy or muddy sediments.

  • They prefer clean, slow-moving or still waters with good oxygen levels.