Most New Zealand native river fish species now threatened: scientist

Most of New Zealand's native freshwater fish species are now threatened or at risk of extinction, a University of Canterbury scientist warned Thursday.

Members of the galaxiid family, which included the heavily- fished whitebait, were especially threatened or at risk, said Dr Simon Howard, who had studied the survival of two threatened galaxiids in catchments of the Waitaki River, the country's second largest river.

Galaxiids made up the majority of native freshwater fish species and New Zealand was home to a third of galaxiid species globally.

"The species I studied appeared to require a specific set of habitat conditions. These conditions are likely to be altered by changes to flow in the rivers they occupy. This makes them vulnerable to changes in flows," Howard said in a statement.

"The change in river flows could also come about via human- induced changes to climate, affecting rainfall patterns and timing. "

The research showed that past and future threats to native fishes included many human activities that altered stream ecosystems, modifying flows and habitats, and introducing invasive species, such as trout.

"There's quite a big difference between what could be done and what's likely to be done which reflects the multiple social pressures on water resources. A cautious approach to altering remaining flows in streams where these fish occur would be a step towards ensuring that their populations persist over time," he said. Endi