The native Canterbury mudfish is on the brink of extinction, a new report says.

Conservation Minister Eugenie Sage released the New Zealand Threat Classification System report on freshwater fish on Thursday, which continues to list the species as "threatened — nationally critical" and says numbers continue to decline.

The small nocturnal fish, one of 21 species of threatened fish belonging to the Galaxiidae family, is found from the south bank of the Waitaki River to the Ashley River in North Canterbury.

"Much of the Canterbury mudfish habitat is on private land and is severely impacted by agriculture. They are found in still or very slow-flowing, meandering streams with deep pools and associated wetlands, spring-fed streams, stock-water races and drains — basically, land-based aquatic environments, whether natural or human-made," Ms Sage said.

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"With a mere 10% of New Zealand's wetlands remaining, it's sad but not surprising that the loss of aquatic and other wetland habitat has had a major impact on Canterbury mudfish and other wetland-dependent indigenous freshwater fish."

The report lists 22 native fish species as threatened and 17 species as "at risk".

There was no change in status for New Zealand's five whitebait species.