A controversial video of a fisherman throwing a small explosive at a raft of sea lions in British Columbia has ignited a heated debated on social media — and prompted an investigation by the Canadian Department of Fisheries and Oceans (DFO).

In the video posted to Facebook, fisherman Allan Marsden is seen lighting a small explosive, referred to as a bear banger and used to ward off aggressive wildlife, and throwing it at the sea lions that have gathered near the boat.

After the explosive detonates, the alarmed sea lions are seen diving under the surface while someone laughs behind the camera.

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The video was shared by several Facebook pages — including the Pacific Balance Pinniped Society, which has been calling to substantially cull the growing population of seals and sea lions off the B.C. coast.

In a Facebook post, the society defends Marsden, who was out with a crew testing for herring roe percentages.

“This is what the herring test boats are dealing with at night right now. Theoretically darkness brings the herring to the surface, which makes it easier to catch them. The test boats are to toss rings with nets and drag up about fifty pounds of herring to sample for roe percentage content from the nets,” the post starts.

“Here is one video showing a bear banger being used to try and get the sea lion horde to move off, so the men can conduct their work. It's always to no avail, for in a few minutes they return. Keep in mind what you hear and see, four times as many are down diving on the massive herring school 20 plus fathoms below the boat,” it continues.

Marsden also explains his actions, claiming the explosion was necessary to deal with the dangerous animals.

"I got bit before. I'm lucky that I'm not in a wheelchair, or worse, dragged overboard and drowned by the sea lion," Marsden said to CTV News. "There's nothing I won't do to protect the crew on this boat. Nothing."

But the crew still was unable to get a live fish for their herring sample.

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Jonathan Wilkinson, the Minister of Fisheries, Oceans and the Canadian Coast Guard, told CTV News Marsden’s actions were “clearly illegal” — though fisherman Thomas Sewid claims it is not illegal.

"There is a conversation going on about the number of seals and sea lions on both the east coast and the west coast, and there's a legitimate conversation to be had about the impacts of that," Wilkinson said. "That is different from a specific example where people are harassing and doing something that is clearly illegal with respect to marine mammals."

Those on Facebook have responded both praising and slamming the video.

“Sad and disturbing! Caught in the act and should be charged!” one person wrote on Facebook.

“Oh my god. Just wow. How cruel and evil,” another shocked by the video wrote.

“That’s not funny…why are they laughing…” one wrote.

“Thomas you are doing a great job shedding light on this topic that most people have no clue what has been happening ..and they wonder why are Herring and salmon have been impacted so badly ... Shared !!!” one in support of the video wrote.

“Man we need to harvest and take our waters back..They are out of control,” one in favor of culling wrote.

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“Too many dang sea lions, they cannot do their jobs as dictated by DFO. Time for DFO to do their job and let we fishers fix the problem by removing the sea lions,” another wrote.

Despite the backlash, the Pinniped society seems happy about how viral the video went.

“Look at the bright side, at least over a million people now know about the plight commercial fisherman are it. Allan is the captain who got bad bite on butt from agrressive sea lion,” Sewid wrote.

Fox News' Michael Bartiromo and Michelle Gant contributed to this report.