The discovery of at least five seals that apparently died in a wayward fishing net on B.C.'s Fraser River has alarmed Vancouver Aquarium's chief veterinarian.

The net and drowned seals were found by a CBC crew on Thursday, Sept. 6, while they were producing an unrelated story on the lower Fraser River near Steveston.

"Those animals likely drowned in that gear, and that's an absolutely horrendous way to go," Martin Haulena told CBC News after he was shown footage of the find.

"It's a very tragic thing when animals die because of direct actions of humans."

One conservation advocate described the material as a "ghost net," a term for lost or discarded fishing gear that harms wildlife.

Joel Baziuk, a White Rock resident and global campaign manager with World Animal Protection, which specializes in the issue, says studies show ghost nets are playing a destructive role in the ongoing worldwide decline in fish populations.

"I see that it was a gillnet and they are the worst in terms of if they get lost, the damage they can do to marine life," he said.

The discovery was immediately reported to Fisheries and Oceans Canada, which later released a statement saying they had investigated and recovered the net.

"The nets had no tags or identification information and the owner of the net remains unknown at this time," the DFO told CBC.

At least five dead seals were visible to the CBC crew that found the animals drowned and decomposing. (Chris Corday/CBC)

Ghost nets

Baziuk said the nets, which are used to fish for salmon, are extremely light, strong, and tend to float high in the water column but just below the surface.

"The mesh is so thin you can't see it, so creatures don't know it's there to avoid it."

Since ghost nets usually can't be seen above water, Baziuk said it's a largely hidden problem, even to those out on the water.

His organization points to statistics revealing a colossal problem, with at least 640,000 tons of fishing gear being lost or abandoned in the world's oceans every year.

It's unclear how long the net had been in the river, or who it belonged to. (Chris Corday/CBC)

'Pile of bones underneath'

Due to ocean currents, gear can stray thousands of miles, Baziuk said, entrapping birds, mammals, fish and turtles. The plastics used in the gear can survive up to 600 years in the ocean.

Some nets found by scuba divers reveal a harrowing history.

"When there's been a net there for a long time there will just be a pile of bones underneath it because it's been fishing for a long time," he said.

Baziuk, who fished commercially for 16 years said crews don't like losing gear because it costs them money and they're increasingly aware of the impact.

"They're not the villains here."

Hundreds of ghost nets recovered in Washington State

Baziuk says 90 organizations and at least a dozen countries are formally working on the problem, largely trying to prevent additional gear from entering the oceans.

Fur seals, sea lions, and humpback and right whales are among the animals most frequently reported wounded and killed by items ranging from nets to prawn trap lines.

Experts say it's tough to estimate the toll because many deaths happen in the open ocean far from human observation.

One study looked at 870 ghost nets recovered off Washington State in the U.S. They contained more than 32,000 marine animals, including more than 500 birds and mammals.

Net entanglements are an issue around the world, including in Scotland, where rescuers recently saved this gray seal trapped in a fishing net. (Scotland SPCA)

'Incredibly sad'

Elaine Leung, a biologist and founder of Sea Smart, a B.C. organization which educates young people about the problem of ocean debris, called the find of dead seals "incredibly sad."

"Most times, we don't see these entanglements because the fishing gear has been washed far offshore or in areas where there aren't many humans," said Leung.

As for the net spotted off Richmond, Baziuk wonders what happened to it.

"Maybe somebody picked that net up, maybe it's still out there. It's hard to say."

The organizations encourage people who spot wayward fishing gear to report it by contacting authorities or by using the ghost gear app.