Whanganui Museum: Managing whitebait - a species in decline

Before the introduction of exotic species such as trout, whitebait were the dominant freshwater fish family in Aotearoa.

MUSEUM NOTEBOOK

In Aotearoa, whitebait are juvenile forms of six different fish that migrate into streams or other waterways where they will grow to adulthood.

These karohe (whitebait) are the tiny, transparent young of our native fish.

Traditionally karohe were caught in great quantities in the Whanganui region during their seasonal migration upriver.

They could be seen clouding the water as they entered the estuary from the sea.

The destruction or pollution of their spawning grounds has dramatically reduced fish numbers in this region.

Five of these species belong to the Galaxiidae family, named for the beautiful galaxy-like markings on the adult fish.

Fibreglass model of adult Galaxias argentus, the giant kōkopu

Before the introduction of exotic species such as trout, they were the dominant freshwater fish family in Aotearoa.

Īnanga are small fish found in lowland and slow-moving streams throughout Aotearoa.

Their larvae are washed out to sea from river estuaries in the autumn and return as juveniles in the spring to form a major component of the whitebait fishery.

Giant kōkopu are the largest of the Galaxiidae family, reaching 400 millimetres or more in length.

These secretive native fish occur throughout New Zealand but numbers are threatened by swamp clearance and introduced brown trout. Larvae hatch in freshwater and go to sea, returning as whitebait in the spring.

Banded kōkopu occur New Zealand-wide and are often called "golden bait" by whitebaiters.

Their larvae migrate to sea, returning in spring as whitebait and grow to maturity in freshwater streams.

They are good climbers and can make their way upstream until they find small forest streams with plenty of cover and shade.

Shortjawed kōkopu are secretive and nocturnal.

They occur throughout Aotearoa, and although they can climb substantial falls and penetrate long distances inland in search of shady places, they need to be accessible to the sea. Juveniles make a minor contribution to the whitebait fishery when they migrate from the sea upriver in spring.

Kōaro occur in localities accessible to the sea and can reach considerable altitudes as they climb up streams in search of shady places with lots of cover.

The juveniles form the second most important species in the whitebait catch when they migrate from the sea upriver in the spring.

The sixth most common species of fish that make up the whitebait numbers in a catch is the Ngaore, or common smelt (Retropinna retropinna), which occurs in estuaries and lowland rivers, spending most of its life at sea.

Landlocked populations can be found in inland and sub-alpine lakes. They are caught with whitebait in some rivers and have a peculiar, strong cucumber smell.

Occasionally other fish species get caught in the whitebaiter's net, including glass eels, the juveniles of native longfin and shortfin eels.

Mounted skin of mature Galaxias fasciatus, the banded kōkopu

Four of these six whitebait species are categorised as threatened or at risk of extinction.

Kōaro, īnanga and giant kōkopu are all at risk and declining while the shortjaw kōkopu are threatened and vulnerable.

This is due to the drainage of wetland habitats, the cutting down of forests, water diversion, poor water quality and pollution and obstructions such as culverts. Protecting habitat, especially spawning areas, will go a long way to providing more sustainable environments for these native juvenile fish.

But do we need to go further?nan

In January 2020 the Department of Conservation released a document proposing changes to whitebaiting regulations and practices.

But New Zealand Forest and Bird reacted strongly, saying DoC proposed measures are not nearly enough. Forest and Bird advocates a catch limit, a licensing system and the compilation of data on how much fish is caught and where.

It is logical that whitebaiting needs sustainable management and that becomes a matter of personal responsibility as well as statutory legislation.

The whitebait pattie is iconic seasonal Kiwi tucker. But should we be catching at-risk juvenile native fish species to fill the national tum?

Some commentators advocate a complete halt to all whitebait fishing in New Zealand.

•Libby Sharpe is Acting Director and Senior Curator at Whanganui Regional Museum.