More links and websites
The National Institute of Water and Atmospheric Research atlas describes freshwater fish in New Zealand.
More suggestions and sources
Collier, Kevin, and Michael Winterbourn, eds. New Zealand stream invertebrates: ecology and implications for management. Christchurch: New Zealand Limnological Society, 2000.
Harding, Jon, and others, eds. Freshwaters of New Zealand. Christchurch: New Zealand Hydrological Society and New Zealand Limnological Society, 2004.
McDowall, R. M. The Reed field guide to New Zealand freshwater fishes. Auckland: Reed, 2000.