A photo of the impaled, flailing fish was uploaded to social media by Hunting and Fishing, Invercargill, with the original caption stating it was a "catch and release" before being edited to remove the claim.
Archie Goldsmith sent the images to the Otago Daily Times, saying Hunting and Fishing was promoting the catch and release of endangered species via spear.
"As a fisher and hunter, I think it’s appalling that a regional leader would promote this. Catch and release with a spear ... They know they’re lying."
He commented on the original post saying it was sad to see a mature longfin eel killed.
"Our grandchildren will miss this taonga ... How about we hunt takahe and kiwi? Just release them after having a 4-pointed barbed [spear] thrown through them."
Hunting and Fishing Invercargill owner Gerald Macrae said the page was for promoting hunting and fishing, and he stood by young people going out and hunting.
"This young fella was out fishing for trout, and here comes a big eel like that ... there’s no harm in it. He wasn’t out there targeting eels."
He said the fisherman released the eel after taking the photo, and watched it swim away.
"That’s what young fellas do, they take fishing rods, they take a spear, all that boy stuff. I would have thought we were promoting that — it’s a whole lot better than ram-raiding."
He understood some of the commenters concerns, and said the post was not intended to antagonise anyone or cause offence.
University of Otago Department of Zoology Associate Prof Mark Lokman said despite the eel swimming away, it likely would have eventually died from its injuries.
From the images, he guessed the eel was between 1.3-1.4m, weighed roughly 10kg, and was at least 40 years old.
The Department of Conservation lists long fin eels as at risk and in decline. It advises them to not be caught.
