Most native freshwater species are threatened in NZ

Most native freshwater species are threatened or at risk of extinction

A University of Canterbury researcher says the majority of New Zealand’s native freshwater fish species are threatened or at risk of extinction.

Among those that are threatened, members of the galaxiid family, which include whitebait, are especially threatened or at risk.

Freshwater scientist Dr Simon Howard has investigated the survival of two threatened galaxiids, upland longjaw galaxias and bignose galaxias, in catchments of the Waitaki River which is the second largest river in New Zealand.

Galaxiids make up the majority of native freshwater fish species and New Zealand is home to a third of galaxiid species globally. Well-known species of the family include the migratory whitebait species (five species in total), but many of the remaining galaxiids are poorly known making conserving them difficult.

Dr Howard says the most threatened fish in the Waitaki catchment is the lowland longjaw which is classified as nationally critical by the Department of Conservation. None of the species Dr Howard researched are well-studied so their role in surrounding ecosystems is unclear.

“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.

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

“My research was focussed on two little-known galaxiid species, bignose galaxias and upland longjaw galaxias. They are both found in the upper Waitaki River. I found that both species were rare across the entire basin and that the regulated hydro river flow influenced whether rivers were dominated by native fishes, or dominated by introduced trout and salmon species.

“After finding both fishes to be rare, more detailed studies showed populations of both species were influenced by in-stream flow conditions.

“My research highlights that past and future threats to native fishes include many human activities which alter stream ecosystems, modifying flows and habitats, and introducing invasive species.

“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.

“However, their interactions with trout still remain a problem, although more active and controversial approaches could be applied, including trout removal and the installation of barriers to limit trout re-introduction and movement.

“Most importantly, my work shows that threats to native fishes often act together, making these fishes especially susceptible to many human activities in and around streams. There are many pressures on the fish.”

Dr Howard graduated with his PhD last year. He is part of the University of Canterbury’s Freshwater Ecology Research Group and his research was supervised by Professor Angus McIntosh.

About 720 students studied biologicial sciences at the University of Canterbury last year, including 120 postgraduate thesis students.

ENDS

© Scoop Media