New Zealand has prolific, cool, clear fresh water of high quality, found in numerous medium to small rivers and streams and low elevation to high country lakes. These waterways carry a highly endemic fish fauna of low diversity (36 indigenous species, 21 exotic species). The indigenous fauna is dominated by Galaxiidae (20 species), whereas the most diverse exotic groups are Salmonidae and Cyprinidae (7 species of each). The steep topography of the country means that the rivers and streams tend to be swiftly flowing, with coarse gravel and cobble, substrates of hard rock, and a high proportion of the indigenous species live within these substrates. About half the indigenous species are diadromous, undertaking regular, seasonally-timed migrations to and from the sea. Fisheries based on the indigenous fauna include modest commercial anguillid eel and galaxiid whitebait fisheries, but probably the chief form of freshwater fisheries exploitation (in overall economic terms) is for New Zealand's world-renowned, recreational angling fisheries for salmonids. Research on the fauna is broadly spread across diverse fields, from studies of the place of freshwater fishes in the community ecology of river and stream biotas as a whole, to focussed studies on habitats of threatened species, design of fish passage facilities for migratory fishes, the effects of introduced exotic species on the indigenous fauna, the impacts of human stream perturbation on aquatic values including fish, and understanding the local ecology of species introduced to New Zealand from other lands.

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