Images of a fish cinched nearly in two by a ring of plastic in Alberta are stirring up online anger — and a biologist warns it's "very common" for wild creatures to be affected in such a way by human garbage.

Fisherman Adam Turnbull pulled the northern pike out of the South Saskatchewan River near Medicine Hat, Alta., on Saturday.

"I thought it had potentially been attacked by another fish," Turnbull told CBC News on Tuesday.

"However, once I picked the fish out of the water I noticed the plastic wrapper wrapped around it, which put me almost straight into shock. I have never seen anything that drastic on a fish before."

It appears the fish had been caught in bottled drink packaging and, while the fish had grown, the plastic had not.

Turnbull, 28, has been fishing since he was 11, and more regularly in the last five years. He said the discovery made him mad.

"For me to say that I have never littered in my past would be a lie. I'm sure we all have at some point. But to see the effects, that fish had struggled for years, definitely struck a chord for me," he said.

He took his outrage to social media, and his Facebook post has been shared thousands of times, with many comments also expressing frustration.

Turnbull said if fish can experience pain, then surely this fish would have.

"I figure every time that fish kicked its tail to move, it was in pain. Every time he moved his body, it moved a little bit and just caused him a little bit more pain," Turnbull said.

"It's horrible really."

A biologist says incidents like the one in question are, unfortunately, quite common, especially near more populated areas.

"On the Great Lakes they have estimated that something like 80 per cent of all of the debris is actually plastic debris of the sort that was depicted in that photo," said Greg Pyle, a University of Lethbridge biology professor.

"It is very common."

Biology professor Greg Pyle says animals getting caught in plastic garbage is more common than most people think. (University of Lethbridge)

He said the fish would have struggled because the plastic almost cut it in half.

"That fish would not have been able to function properly in its natural habitat. It would be impaired in its ability to forage, to catch prey fish, so it would be at a significant disadvantage," he said.

Pyle said it's best, if possible, to remove the plastic and set the fish free.

"Take some time to resuscitate the animal appropriately, make sure it can swim on its own. If it looks like it is struggling, it doesn't look like it is coming back around again, sometimes it is most humane to euthanize it as humanely as possible," he said.

Adam Turnbull was shocked when he realized a fish he caught had been struggling with a piece of plastic garbage for a while. He cut the plastic off and says the fish took off 'like a dart.' (Adam Turnbull)

Turnbull said he didn't have to kill the fish, because when he took the plastic off, it seemed to enjoy its new freedom.

"As soon as that fish touched the water, it took off like a dart."

Turnbull hopes the dramatic photos will get people thinking.

"Pack out what you pack in," he said.

"I don't know how many times I am walking the shoreline and I find cans or bottles or minnow tubs or bags that were used to hold worms for fishing. It's just a real problem. Me personally, I always bring a grocery bag and pick up a few things on the way."