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The Mosgiel man, who did not want to be named, was hunting wild pigs in the upper Taieri at the weekend, when the incident happened.
Four of the dogs which perished belonged to him and one dog belonged to a "mate".
Together, they were worth about $10,000, he said.
The dogs entered the river behind the pig but, while they would normally be able to scramble out, about 3m of ice on either side of the river prevented their escape.
"I couldn't do anything.
"There was ice in the middle of the river too.
"I could only watch them float past," the hunter said.
He believed the cold got to the dogs and they died quickly.
The cold, icy conditions were unlike anything he had seen before, even though pig hunting normally took place in rugged places.
"You don't catch pigs in a paddock," he said.
It could be a dangerous activity for dogs, which sometimes died after fighting with pigs, the hunter said.
Mornington Tavern owner David "Murdoch" Miskimmin helped organise Otago's largest annual boar and deer hunt held over the weekend.
He said it was rare for dogs to be killed while hunting.
Even if they were "ripped" by boar tusks, they usually recovered.
Mr Miskimmin said hunting dogs were highly trained and kept in premium condition, hence they were very valuable to owners.
"Some people might think they aren't treated very well, but that's certainly not the case.
"A good pig dog is worth its weight in salt.
"You don't get a lot for two and a half thousand [dollars], put it that way," he said.
"If you could ask the dogs they wouldn't swap their life for anything.
"They absolutely love it.
"Most guys are very good with their dogs."
The hunt, from early Friday to 3pm yesterday, was otherwise without incident.