A Southland fish exporter says using electricity to indiscriminately stun fish was like ‘‘tasering a two-month-old baby’’.
Mossburn Enterprises owner Victor Thompson said many organisations in Southland regularly used electricity to stun fish in fresh water.
A 240-volt generator with a strong electric pulse stunned every fish within a 3.5 metre radius, Mr Thompson said.
‘‘It’s like tasering a two-month-old baby.’’
The sudden impact could dislodge the backbone of a fish, he said.
Some fish, like eels, could be buried under mud and gravel so when they were stunned they would not rise to the surface and were stunned repeatedly, he said.
Fish and Game senior fish and game officer Zane Moss said Fish and Game had used a backpack electrofisher in Southland for more than 20 years.
Fish and Game used electrofishing to survey the abundance and health of fish in Southland waterways.
The electrical current forced the fishes muscles to activate and made them swim towards the current, Mr Moss said.
Stunned fish where then netted out of the charged waterway and placed into a bucket of water, where they quickly recovered, he said.
Electrofishing was commonplace in New Zealand and used by the Conservation Department, NIWA and regional councils, he said.
The current used to stun the fish was so small that a Fish and Game officer had electrofished barefooted in a remote waterway because they forgot to put gumboots in the helicopter, he said.
The National Institute of Water and Atmospheric Research (Niwa) group manager Marty Bonnett said Niwa had about 10 backpack electrofishers across New Zealand.
Electrofishing could cause spinal damage to trout, Mr Bonnett said.
The electric current caused an unnatural action in the fish that could dislocate the spine, he said.
The backpacks were most effective in less than 1-metre of water and released a charge like a bright light bulb, he said.
Bigger fish got a bigger charge because they had more surface area, so an adult eel got more of a shock than a whitebait, he said.
Waikato University technical manager of biological science Dudley Bell said the university owned a 4.5-metre long electrofishing boat.
The boat released a 3-metre-wide charge, up to 1000 watts, and and was used in lakes and rivers across the North Island.
The boat usually released a 10 minute charge of electricity in the water but he had seen a five second charge stun 50 carp when electrofishing in Huntly, Mr Dudley said.
Electrofishing was a better way to catch fish than nets because nets indiscriminately killed fish, he said.