Story: Freshwater fish

Page 3. Galaxiids: īnanga and kōkopu

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Most native freshwater fish species are called galaxiids (from the family name Galaxiidae). There are seven genera in the family and two (Galaxias and Neochanna) occur in New Zealand. The name refers to their profusion of small, silvery-gold spots, which were compared to the stars in a galaxy by those who first identified them.

In New Zealand there are at least 25 species in this family. New species are still being discovered, with eight recognised since the early 1990s. Galaxiids are a fascinatingly diverse group. Most are shy creatures that few people ever see. A small number of enthusiasts find them appealing and keep them in captivity.

Galaxiids have no scales, and their dorsal fin lies toward the rear of the body. The main fins form a propulsion unit towards the tail, making them adept at rapid acceleration and short bursts of speed, though not so well designed for long-distance swimming.

Īnanga

The most widespread and best known of the galaxiids is īnanga (Galaxias maculatus). Unlike most of its relatives, it is the one Galaxias species that lives in the open waters of pools. It swims in smallish, roving shoals, in pools and runs of lowland rivers and in wetlands.

Small fry

Many New Zealanders consider whitebait a delicacy, with its sweet, tender flavour. Often lightly cooked in fritters, the tiny fish are eaten head and all. They fetch a high price in the netting season.

In their juvenile form, īnanga are well known as the chief species in the whitebait fishery, which is made up of juvenile fish of five different Galaxias species. They are conspicuous to fishermen, especially towards the end of the whitebait season, because they have grown larger and developed pigmentation.

They are robust, silvery-green fish, easily kept captive but rather subdued as aquarium specimens. They commonly grow to around 10 centimetres and are most abundant in rivers over summer.

Life cycle

Most īnanga live for just one year. Large shoals of adults gather and migrate downstream at about the time of autumn tides, spawning when these higher tides flood the grasses that line estuary shores.

Once fertilised, the eggs settle down into the grass. When the tide recedes they are exposed to the humid atmosphere among the grasses, and develop there over the following weeks. Some hatch at the next set of high tides (around two weeks later). In cool weather, development may take longer, and they may not hatch until there have been two sets of high tides (around four weeks after being spawned).

Tiny larvae hatch when re-immersed in the rising tide. As the tide falls again, they are swept into estuaries and carried out to sea. There they spend winter, returning to fresh water in spring as the familiar whitebait.

Banded kōkopu

Some other species of Galaxias are fairly well-known. The banded kōkopu (G. fasciatus) is another of the whitebait species, with adults commonly growing to around 20 centimetres. It is known as ‘native trout’ or ‘Māori trout’ – but it is no trout.

It is greyish-brown with vertical pale bands across its sides – providing camouflage in the dappled light on small bush streams. Banded kōkopu inhabit pools in the smallest streams, some of which are only half a metre wide with scarcely enough room for the bigger fish to turn round. When people live nearby, the fish can be quite tame, taking food from the surface of pools, and even jumping to take it from your hand.

Banded kōkopu as pets

They are beautiful fish, but successfully keeping them is difficult as they suffer from a fungus growth that develops if their body’s mucus layer is damaged. It is best to catch juveniles at the whitebait stage and rear them. To achieve this you have to know what a banded kōkopu whitebait looks like, and that is a skill in itself.

How to cite this page:

Bob McDowall, 'Freshwater fish - Galaxiids: īnanga and kōkopu', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/freshwater-fish/page-3 (accessed 20 November 2018)

Story by Bob McDowall, published 24 Sep 2007