The delineation of natural areas in New Zealand: Natural areas in the distribution of freshwater fish

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New Zealand possesses some twenty species of native freshwater fish, but they have been so little studied that natural areas based on their distribution cannot yet be defined. More is known of the distribution of the introduced fish and this paper deals with the the two main species.
These are brown and rainbow trout. They were introduced about 1870 and 1884 respectively and rapidly became established so that by 1900 a clear distribution pattern had emerged. Each species became dominant in part of the country and four main geographical regions can be distinguished-two dominated by rainbow trout and brown trout respectively and two practically devoid of trout.