The commercial fishing industry has long claimed it strives to ensure salmon that can't be legally kept are released alive and well.
But a video shot by a conservation group in British Columbia shows seine boat crews kicking salmon across decks, or waiting for fish to stop moving before picking them up and throwing them overboard.
In a season where there have been widespread concerns about low numbers of some stocks, particularly sockeye and chum salmon, the video is expected to stir controversy.
An industry spokesman has dismissed the video as misleading, however, and says fishing crews are "doing a good job" of ensuring the safe release of fish that are accidentally taken in a by-catch.
"I'm sure that they have cut the footage that they took to try and emphasize the point they are making," Rob Morley, vice-president for the Canadian Fishing Company, a subsidiary of the Jim Pattison Group, said Thursday. "And I think the majority of the crews are doing an extremely good job in handling a very small volume of by-catch."
Mr. Morley, whose company owns most of the seine boats on the West Coast, said fishing crews are told they have to obey Fisheries and Oceans regulations, which require the prompt and safe return to the water of all prohibited species.
But he says crews handle a lot of fish and can't always immediately get to the species that have to be released.
In Area 6 on B.C.'s central coast, where the video was shot, he said boats have scooped up about seven million pink salmon so far this season, typically taking 20,000 salmon a day, of which only about 200 might be prohibited species.
Mr. Morley said he's convinced the crews "in general" are doing a good job of releasing fish.
But Aaron Hill, the man who shot the video, says it provides clear proof of abusive behaviour on the fishing grounds.
"We've known this has been happening for a long time, but we finally have evidence," said Mr. Hill, a biologist with Watershed Watch. He took the video in the Great Bear Rainforest, near Hartley Bay.
Mr. Hill said the fishery, the largest on Canada's West Coast this year, is targeting pink salmon but other species – including sockeye and chum – are mixed in because the runs overlap.
Mr. Hill said federal regulations require fishermen to quickly and safely return to the water any species accidentally taken.
But he said he followed three seine boats and was alarmed to see fish being abused on all of them.
Mr. Hill said salmon should be sorted on a table on a boat's deck and fish should be returned to the water down a tube or slide.
Instead he saw salmon thrown overboard, apparently lifeless, or kicked across the deck, ricocheting off metal railings.
"There's no doubt those fish were goners," he said.
Mr. Hill said that after a fish has been out of the water for more than one minute, the chances that it will die are extremely high.
But the video shows the crew on one boat walking away from fish that have been dumped on the deck. They don't go back to release the non-target salmon until the fish have stopped moving, nearly three minutes later.
"Even if their hearts were still beating, they would not be in any shape to avoid predators, let alone migrate up a river to spawn," Mr. Hill said.
"I know in some fisheries they do take measures to safely release fish, but this raises the question if it's happening all the time," he said. "And it's just a total waste."
In the video, Watershed Watch urges people to write to Fisheries Minister Gail Shea and to the Jim Pattison Group.
DFO was not immediately able to provide comment.