A Taieri Gorge Railway employee is fed up after the second "bizarre" incident in which a live eel has been dangled from a rail bridge and hit by a train.
Co-driver Paul Jeffery said a live eel was first strung up from an Abbotsford bridge using fishing line three weeks ago and then again on Monday.
On both occasions, the wriggling eels were killed upon impact with the locomotive and two youngsters, aged between about 11 and 14, were seen running off as the train approached, Mr Jeffery said.
"The locomotive smacks into it and you can see it's still moving and it cuts the fishing line as we hit it and it fortunately kills the eel," he said.
Mr Jeffery labelled the youngsters' actions as cruel and feared they could be a "precursor for doing something worse".
Police were contacted after both instances.
In the most recent case, the train operators buried the eel at sea after dropping passengers, who were from the Celebrity Solstice cruise ship and unaware of the incident, at the Dunedin Railway Station.
In the second instance, the eel was much larger and believed to be a longfin eel, which could live more than 60 years.
"I was just reading about [longfin] eels and they are actually quite intelligent creatures."
Taieri Gorge Railway operations manager Grant Craig said this was the first he had heard of eels being dangled in the path of oncoming trains.
"It's usually stones and rocks, but eels are something new," he said.
Dunedin freshwater fish specialist Dr Terry Broad, who did his PhD on the habitat of longfin eels, confirmed after looking at a photograph of the dangling eel that it was a longfin - a species that was struggling to survive - and by its size was probably a female and possibly up to 30 years old.
Parliamentary Commissioner for the Environment's Dr Jan Wright recently released a report showing the native longfin eel is on a "slow path to extinction".