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What lives in the Waikato River?

The Waikato River is home to a much wider variety of plants and animals than many people realise. There are at least 19 types of native fish, 10 types of introduced fish, and many aquatic invertebrates and plants living in the Waikato River and its associated wetlands and lakes.

Photograph of a banded kokopu

On this page:  native fish, introduced fish, river invertebrates, hydro lakes, threats to life in the river

Native fish

The Waikato River and its associated wetlands and lakes are home to many different types of fish, including 19 native species. The river supports a large recreational whitebait fishery and a large commercial eel fishery. The table below lists native freshwater fish and crustaceans found in the lower Waikato River catchment.

Table 1: Native freshwater fish and crustaceans of the lower Waikato River catchment

Common name (Māori name) Scientific name
Yellow-eyed mullet (aua) Aldrichetta forsteri
Shortfin eel (hao) Anguilla australis
Longfin eel (Kuwharuwharu) Anguilla dieffenbachii
Australian longfin eel Anguilla reinhardtii
Lamprey (pirahau) Geotria australis
Torrentfish (papamoko) Cheimarrichthys fosteri
Giant kokopu (kokopu) Galaxias argenteus
Koaro Galaxias brevipinnis
Banded kokopu (para) Galaxias fasciatus
Inanga Galaxias maculatus
Short-jawed kokopu Galaxias postvectis
Black mudfish Neochanna diversus
Giant bully Gobiomorphus gobiodes
Common bully (pako) Gobiomorphus cotidianus
Redfin bully Gobiomorphus huttoni
Cran’s bully Gobiomorphus basalis
Grey mullet Mugil cephalus
Common smelt (ngaoire) Retropinna retropinna
Black flounder (patiki) Rhombosolea retiaria
Freshwater crayfish (koura) Paranephrops planifrons
Shrimp (kouraura) Paratya curvirostris

Many of New Zealand’s native freshwater fish are migratory and need access to the sea or an estuary during their lifecycle. Barriers such as dams and poorly installed culverts can stop these fish from being able to successfully migrate to their breeding grounds or adult habitats. Find out more about fish access.

Natural obstacles such as waterfalls and rapids can also limit fish access. Even before the Waikato River dams were built, few migratory fish would have managed to reach the current location of the Arapuni hydro dam because of the very large rapids in the area.

Introduced fish

The Waikato River and its associated wetlands and lakes now contain at least 10 introduced fish species, and support a winter trout fishery.

Some introduced fish, such as koi carp and Gambusia, have become major pests. Find out more about these troublesome fish. The table below lists introduced freshwater fish found in the lower Waikato River catchment.

Table 2: Introduced freshwater fish found in the lower Waikato River catchment

Common name Scientific name
Catfish Ameiurus nebulosus
Goldfish Carassius auratus
Grass carp Ctenopharyngodon idella
Koi carp Cyprinus carpio
Gambusia or mosquito fish Gambusia affinis
Rainbow trout Onchorhycchus mykiss
Perch Perca fluviatilis
Brown trout Salmo trutta
Rudd Scardinius erythropthalmus
Tench Tinca tinca

River invertebrates

Photograph of a freshwater crayfish (koura)

Invertebrates are animals without backbones. They include insects, snails, worms and crustaceans, such as koura (freshwater crayfish). Different types of invertebrates live in different parts of the River, depending on the water quality and the river bed substrate, for example, whether the river bed is sandy or rocky.

Soft shallow shorelines are usually covered by under water plants. They provide a home for damselfly larvae, small fish, snails, fine algae and beetles. Rocky areas in shallow parts of the River are home to small filamentous algae and sponges.

Hydro lakes

The plants and animals in the hydro lakes along the Waikato River are quite different to those that live in flowing parts of the river. The hydro lakes contain:

  • A wide variety of fish, including brown and rainbow trout, catfish, smelt, rudd, common bullies, elvers (baby eels), goldfish and carp.
  • Other animals including freshwater sponges, insects and snail larvae, pea mussels and freshwater mussels.

Plant-life in and around the lakes consists of:

  • Hornwort and the oxygen weed Egeria densa are the most abundant aquatic plants.
  • Sweetgrass, bull rush, raupo and assorted reeds along the lake shores.
  • Deeper down (10 to 30 metres), the algal cover on plants and rocks fades out as light levels decrease.

The eight Waikato River hydro lakes are:

  • Lake Aratiatia
  • Lake Ohakuri
  • Lake Atiamuri
  • Lake Whakamaru
  • Lake Maraetai
  • Lake Waipapa
  • Lake Arapuni
  • Lake Karapiro.

Threats to life in the river

  • High levels of sediment, which reduce light levels needed for plant growth (photosynthesis).
  • Low levels of oxygen in the water for fish to breathe (a result of pollutants that consume oxygen as they break down).
  • High levels of nutrients such as nitrogen and phosphorus, which promote the growth of nuisance plants, shading out or out-competing native species.
  • Introduced pest fish that feed on native species and/or destroy their habitat.
  • Barriers to fish migration, such as dams without fish passes.

Find out more about water quality for plants and animals in the Waikato River.