Fish & Game teams throughout the country have been sweeping rivers and streams with a pole that emits a low-voltage, high-current charge.
Fish drawn towards the charge are stunned temporarily and scooped up in a net.
They are identified, weighed and measured, before being returned to the water.
The electric fishing programme helps Fish & Game monitor populations of trout and salmon, and record native freshwater fish such as various species of galaxiids, koaro, kokopu, bullies, eels, torrentfish, lamprey and koura.
They also note waterway conditions, macroinvertebrates and barriers to fish movement.
Data is entered into Niwa’s New Zealand freshwater fish database for use by other freshwater scientists and to inform both regional and national policy.
"Electric fishing is helping to protect New Zealand’s freshwater fish and rivers," Fish & Game chief executive Corrina Jordan said.
"It may sound unusual, but it’s an effective way to keep watch on the state of our fish species, including indigenous populations, and the places they live.
"These surveys support other research that show native fish populations, as with juvenile trout, are at risk from the increased frequency and size of flooding.
"Monitoring identifies waterways with declining water and habitat quality, and the effects of barriers to fish passage.
"This important programme also sees Fish & Game staff connecting with local communities, land owners and partners."
Under the Resource Management Act, the management of physical resources must have regard to the protection of the habitat of trout and salmon.
Fish & Game mostly uses electric fishing to confirm the presence of juvenile trout, a marker of successful spawning.
"Because juvenile trout stay within the stream their parents spawned in, any observation proves that trout spawning occurred somewhere within the reach or further upriver.
"The presence of trout means Fish & Game can advocate for that habitat, which benefits all aquatic life — native and valued introduced species."
Electric fishing is also used to educate school and catchment groups about stream habitat and health.
Fish & Game also shares data with agencies such as the Department of Conservation for resource consents and partners with universities on electric fishing monitoring projects.
"As river guardians, Fish & Game has been gathering and sharing data for over 30 years and will continue monitoring in future for the benefit of all freshwater fish species."
In Otago, Fish & Game staff electric fish survey between 20-30 rivers and streams annually.
This summer, the staff worked on the Shag/Waihemo River, lower Clutha River tributaries, the Catlins and Owaka rivers, Waters of Leith, Lindsay Creek, Silver Stream, Kaikorai Stream and Thompson Creek.
— Staff reporter
