Filmmaker Marina Dodis didn’t set out to make an information-heavy documentary about salmon spawning in Metro Vancouver. While shooting “The Return” in the Brunette watershed, which includes Stoney Creek along Burnaby Mountain and Still Creek in Burnaby and East Van, she aspired to create an immersive experience for viewers.

That’s clear from the opening of the film, which will be shown at the Vancouver International Mountain Film Festival. The sequence features a man paddling a canoe and dropping a basket into a creek to capture smolts, then measuring them amid burbling sounds of water. Animation shows the route these fish take out of the watershed to the Pacific Ocean. That’s followed with imagery showing the industrial hub, highways, and SkyTrain lines near the Fraser and Brunette rivers in New Westminster. Not a word is spoken in the first three minutes.

It doesn’t seem possible that tiny fish could survive in such a densely populated urban environment, but they do, thanks to the volunteer efforts of the Burnaby Streamkeepers.

“Now I look at all of those big, multicoloured oil slicks with gasoline on the road and I think of salmon—all the time,” Dodis tells the Straight by phone.

Along the way, the characters in her 20-minute documentary deliver a detailed lesson in how some salmon survive against all odds.

Musqueam band aboriginal fisheries officer Morgan Guerin takes viewers through the history of the tidal basin, explaining why salmon find it more difficult to rest now that back eddies have been removed.

Dianne Ramage, director of salmon-recovery programs for the Pacific Salmon Foundation, reveals how internal homing systems enable salmon to migrate to their home streams through a muddy river, passing tugboats, rapid-transit lines, shopping malls, and housing developments.

Writer J. B. MacKinnon provides illuminating commentary about how the pace of development alters human perspectives about the natural world. And aquatic biologist Mike Pearson talks about why chum salmon have been able to spawn in East Vancouver for the first time in many decades.

Then there’s John Templeton, a member of the Burnaby Streamkeepers. Knee-deep in water, he tells Dodis that back in 2004, he cleared all the debris along Stoney Creek.

“That year, fish made it up to spawn here,” Templeton says. “We’ve had fish here every year since.”

The film also provides insights into how roadway salt, which runs into the watershed during heavy rains, diminishes salmon survival rates. Urban density is also a villain in the piece, inhibiting the drainage of water that can ultimately benefit the fish.

Dodis tells the Straight that her motivation for making “The Return” was to persuade local residents to become more curious about what’s going on in their backyard. She believes that if people learn how their actions can yield almost immediate results, they’ll be more likely to get involved.

“Trying to protect things that are really far away is not very successful,” she says. “It’s difficult to do.”

Ideally, Dodis would like a younger person to see her film and then launch a social-media campaign to elevate awareness about the need to preserve Lower Mainland spawning streams.

“You could actually walk along the creek and get information off your phone about where you are—and what you can do and what not to do.”