Where are the fish?
New Zealand has an abundance of cool clear rivers, streams and lakes, but if you look into the water you will not usually see many fish. The journals of many early settlers refer to empty rivers. Believing there were no native fish, they introduced trout and salmon – species that would meet their expectations as game and a source of food. But it was a mistake to think the rivers were empty, as Māori had long caught a wide variety of native fish.
Ousted by trout
New Zealanders are more familiar with trout and salmon than with native fish. Trout and salmon were introduced in the late 19th and early 20th centuries. Massive trout populations rapidly developed, with adverse effects on native fish through predation, competition for food and displacement from favoured habitats.
European settlers soon discovered the delight of fresh whitebait, and learned to fish for upokororo (grayling). As Māori knew well, eels were a nutritious addition, and livened up an often plain colonial diet.
Many New Zealanders are surprised to learn that fisheries biologists recognise more than 40 native freshwater fish species. If asked about freshwater fish, most people will mention trout (which are not native), eels, and perhaps whitebait. There is little awareness of the variety of native fish in rivers and lakes.
Secretive and nocturnal
For some reason that scientists do not understand, nearly all native freshwater fish are very furtive creatures. By day they typically live among boulders and pebbles of streams and lake beds, or hide beneath overhanging stream banks, or among logs and woody debris. Most species are also quite small.
New Zealand’s eels are nocturnal, as are many other native freshwater fish. An effective, low-tech way of identifying fish, especially in small streams, is spotlighting – shining a broad-beamed torch into a stream at night to see what is out and about.
The greatest diversity of native fish occurs in small streams – many of them no more than a metre wide. It is not clear why they prefer this habitat. It could be partly because introduced trout have forced them into smaller headwater streams, preying on them or displacing them from their habitats. It is likely that there are other reasons as well.
Freshwater fish are not protected under the Wildlife Act 1953, although native fish are protected in national parks or other conservation lands. For many species, legal protection from being caught is not really an issue as land use and developments that damage their habitats pose far greater threats to their survival. There are some regulations to manage the harvest of eels, whitebait, smelt and lamprey that form small fisheries.