Kokopu

Shaun Lee, CC BY 4.0, via Wikimedia Commons

Kokopu are three types of fresh water fish in the Galaxia genus

Kokupu are endemic to NZ and two of these the Banded Kokopu and the Shortjaw kokupu are found in the Tangihua ranges.

Kokupu do not have scales, but have a leathery, thick skin covered with mucus. A large rounded single dorsal and anal fin are set back close to the large square caudal fin.

Kokupu migrate between freshwater habitat and the marine environment during its life cycle. The fry goes to sea after hatching, and returning as juveniles to fresh water where they grow to adulthood.

Adult Kokupu make their way downstream to river mouths in the autumn to spawn. Thousands of eggs are laid amongst vegetation on river and stream banks flooded by a spring (very high) tide.

Males fertilize the eggs with such large amounts of sperm (milt) that the water turns milky.

When the tide recedes the eggs sit out of water for two weeks or more remaining moist in the vegetation until the next spring tide, when they hatch and larvae are washed out to sea.

After spending four to five months of winter in the ocean, large shoals of juvenile fish (whitebait), up to 5 cm long and 3 to 4 mm wide, swim into river and stream estuaries on the incoming tide in spring.

They make their way upstream in the final stage of an incredible journey for such a small fish, to develop into adult freshwater fish.

Kokopu live for between 5 and 10 years but can reach in excess of 21 years

The difference between shortjaw and banded Kokopu

Juvenile shortjaw kokopu may also be mistaken for a very pale and poorly marked banded kokopu, but the small mouth of the shortjaw is diagnostic

compared to a banded kokupu

• They have an undercut jaw, with the lower jaw being shorter than the upper jaw.

the top is the banded kokupu and the bottom the shortjaw kokopu

photos Photo G.A. Eldon, Crown Copyright © Department of Conservation.

Shortjaw Kokopu

Galaxias postvectis endemic to New Zealand

photos Photo G.A. Eldon, Crown Copyright © Department of Conservation.

Shortjaw kokopu are rare in the Tangihua’s

The shortjaw kokopu is probably the rarest of the whitebait galaxiids and are considered endangered. It is unusual to capture more than a few fish at a given site. It is usually found in streams with large boulders in pool.. Because this fish has been so rarely encountered, little is known about its life history

Description of the shortjaw kokopu

the shortjaw kokopu is a brownish fish with faint bands and blotches. they have a distinctive dark blotch on each side just behind the gills

the shortjaw kokopu may grow to a maximum of 350 mm , but more commonly reach 150–200 mm They have an undercut jaw, with the lower jaw being shorter than the upper jaw.

Life cycle of the shortjaw kokopu

Shortjaw kokopu migrates between freshwater habitat and the marine environment during its life cycle. , the fry goes to sea after hatching, and returning as juveniles to fresh water where they grow to adulthood.

Shortjaw kokopu can travel up to 200 km inland, and reach an elevation of 500 metres in many catchments.

There is a distinct preference for faster moving, small tributary streams with boulders, and complete vegetation cover of native forest, particularly podocarp/broadleaf forest, often podocarp/broadleaf/beech forest, and rarely beech forest. In fact it may be restricted to streams with native forest cover.

During the day it hides in small pools under logs and overhanging banks, or around rocks, with the overhead canopy of native riparian plants. Shortjaw kokopu are nocturnal feeders, mainly of terrestrial invertebrates such as spiders, ants, caterpillars and moths that fall onto the water surface, and caddisfly larvae from boulders.

An effective method of finding them is proving to be by spotlight at night.

Banded Kokopu

Galaxias fasciatus endemic to New Zealand

Description of the banded kokopu

commonly grows to 20–25 cm, but has been recorded growing to around 30 cm. Juvenile banded kokopu are good climbers and can climb up waterfalls and other vertical surfaces by moving into the splash zone and wriggling up the surface, using the water surface tension and their large downturned fins for grip.

Juvenile banded kokopu develop well defined vertical bands on their sides and over the back early on. The bands become less prominent towards the front, but remain in the tail area of large adults.

Adults are usually a dark, earthy brown or olive brown, with pale yellow vertical bands along the body. The belly is light coloured and unpatterned. Behind the operculum and above the pectoral fin is a silver or white mark, and sometimes a darker mark behind this. The bands either fade out top and bottom, or fork and crisscross the back of the fish.

In small fish the bands are usually numerous and along the whole body, but in adults the bands become narrower and are often restricted to the rear third of the body. Although the bands change as the fish ages, the placement and shape of the bands are consistent enough to be used for individual identification over several years.

Banded kokopu are the smallest whitebait, but will often mature to a length of 20 cm, and sometimes reach 26 cm. Whitebaiters call them “golden bait” because of their golden colour as whitebait.

Life cycle of the banded kokopu

Juveniles are good climbers, quite able to move upstream to small tributaries that have a good cover of forest canopy. This provides shade and hiding protection the fish require during the day, and protects their invertebrate food source.

Banded kokopu are concentrated in Northland, Auckland and the Coromandel

Banded kokopu are primarily a coastal species but will penetrate 180 km inland, up to an elevation of 550m.

Banded kokopu are nocturnal, feeding on terrestrial ants, weta, spiders and beetles that end up in the water course, and invertebrate lavae of caddisflies and mayflies

Banded kokopu become sexually mature at two or three years old and can live for at least nine years possibly longer, and spawn multiple times over their lifetime. . Males mature at 2 years of age while females mature at 4 years

commonly grow up to 200 mm , which are likely to be about 7 years of age based on average growth rates but often grow to 260 mm

Threats and conservation

Deforestation, draining of swamps and introduced trout has made a major impact on kokupu numbers.