Whitebait biology

What's in a whitebait fritter?

Whitebait, those tiny, transparent creatures found navigating our streams, are the young of some of New Zealand's precious native fish. Some of the species you are likely to catch in your whitebait net are inanga, kōaro, banded kōkopu, giant kōkopu, shortjaw kōkopu, smelt, bullies and juvenile eels.

The first five (which belong to the Galaxiidae family) and common smelt are legally considered whitebait, while the other species are considered bycatch.

Galaxiids

The Galaxiidae family was named after the Milky Way galaxy, as the very first species described was sprinkled with dazzling spots. Although galaxiid species are found in many places in the Southern Hemisphere, the giant, shortjaw and banded kōkopu only exist in New Zealand. Our galaxiids are generally nocturnal and very good at hiding.

The main breeding season for our galaxiids is autumn. Inanga migrate downstream to estuaries and lay their eggs among plants and grasses, whereas kōaro and kökopu stay where they are and lay their eggs on leaf litter and forest plants. The eggs stay out of water for several weeks, and need good plant cover to keep moist. They hatch when re-immersed by spring tides (for inanga) or floods (for kōaro and kōkopu). The larvae then float out to sea, where they live and grow over winter, migrating back upstream as whitebait in spring.

Inanga

Inanga (Galaxias maculatus) - Declining

Inanga are small and short-lived, with most only surviving for 1 year and reaching around 100 mm in length. They are found in a wide variety of habitats, from tiny creeks, to coastal rivers, lowland streams, lakes and wetlands. Unlike other galaxiids, they swim together in shoals.

Found in places as far flung as Chile, Australia and Argentina, inanga are the most widely distributed native freshwater fish in the world. They are New Zealand's most commonly caught species.

Giant kōkopu

Giant kōkopu (Galaxias argenteus) - Declining

Giant kōkopu is the largest galaxiid species in the world-with individuals usually reaching 300-400 mm long. They are slow-growing and can live for more than 20 years. Generally found close to the sea, they inhabit wetlands, lakes and forest streams.

Giant kōkopu rely on good bush surrounds-they are skulking predators, lurking under cover and making speedy dashes to nab their prey. Like the banded kōkopu, giant kōkopu are also called native or Māori trout.

Banded kōkopu

Banded kōkopu (Galaxias fasciatus)

Also called Māori or native trout, banded kōkopu have pale vertical stripes across their sides and most grow to around 200 mm long. They need sheltered streams to survive-dwelling in pools with overhanging banks, logs and boulders.

Like other galaxiids, banded kōkopu have sensors on their heads to detect when and where something hits the water, enabling them to feed on insects that fall from overhanging plants. They are good climbers and can be found up to 550 m above sea level.

Shortjaw kōkopu

Shortjaw kōkopu (Galaxias postvectis) - Declining

Unique to New Zealand, shortjaw kōkopu are rare, secretive and seldom seen. They have an undercut jaw, designed to scrape aquatic insects from rocks. Shortjaw kōkopu usually grow to between 150 and 200 mm.

They can only survive in certain types of habitat, many of which have been degraded by forest clearance, which has probably contributed to their rarity.

Kōaro

Kōaro (Galaxias brevipinnis) - Declining

Kōaro are accomplished climbers, being able to negotiate near-vertical waterfalls using specially formed broad fins that have a grippy texture underneath. Living for 15 years or more, kōaro travel as far as 400 km inland and climb as high as 1300 m.

These solitary fish are found in fast-flowing, cool, tussock or forest streams and grow to about 160-180 mm. In bright light, their skin shines with iridescence.

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