New Zealand scientists are hoping tags on 10 longfin eels will help them pinpoint where in the Pacific Ocean they go to spawn.
Migrating longfin eels develop particular physical characteristics including a blue ring around the eye. Their stomachs shrink and they cease eating. Photo: Stuart Mackay / NIWA
Listen to an interview with Paul Franklin on Dateline Pacific
NIWA freshwater ecologist, Paul Franklin, said it was a mystery where exactly the female eels swim to, to begin their life cycle.
He said previous research indicated a likely breeding zone somewhere between Tonga and New Caledonia.
Dr Franklin said electronic tags were being fitted to the eels in Te Kauwhata near their home in New Zealand's Waikato river and the tags are programmed to release at certain time intervals.
The longfin eels are endemic to New Zealand and can grow up to two metres long and weigh up to 25kg with a lifespan of around 60 years.
Scientists expect it will take the female eels several months to reach their predicted location, then once they arrive, they spawn and then die, leaving their larvae to be transported back to New Zealand on ocean currents.
Releasing a tagged female longfin eel at dusk at Port Waikato. Photo: Stuart Mackay / NIWA