[Reporter: Greg Rasmussen] In search of the elusive sea otter.
Tough to spot in the waters near the northern tip of Vancouver Island.
Usually out of these reefs we have otters.
[Reporter] It's critical to find and count them to document their growing impact on the ecosystem.
Yeah, there is one lying on his back right.
Right on, oh yeah.
Got him.
He's up in the air.
[Reporter] Once wiped out entirely in B.C. by the fur trade
they are now making a comeback.
Now I see two more heads in there.
A little closer to us right in the kelp.
One, two so right now I see a female with a pup and the mom's just come up.
She's giving her head a shake.
Given their history as targets
they have good reason to be wary.
They can smell us from here.
They can probably hear the motor and the wind is blowing us right
so you can see their heads just trying to get away from us.
[Reporter] Researcher Erin Foster takes advantage of a calm day.
I think it's just behind the rocks.
[Reporter] To go ashore and count groups of otters called rafts.
On this trip we come across a growing colony of nearly 60 animals.
They look like they're scared actually.
But sometimes the wind will blow the raft apart a little bit.
[Reporter] Despite their cute and fuzzy looks otters are a top predator
eating kilo after kilo of shellfish every day.
Gooey duck, clams, urchins, crabs and other underwater creatures.
So what am I looking at?
Yeah so I mean my guess would be he's a territorial male.
He's quite fat.
Another one's not so shy as a lot of them.
And he's checking us out.
He's looking right at us.
He definitely knows we're here.
And he looks very big and healthy.
[Reporter] Their luxurious pelts made them a target for the fur trade starting in the 1700s.
Once in the tens of thousands they were wiped out
with the last known otter in bc shot in 1929.
But their return wasn't by accident.
50 years ago, Canadian Biologists traveled to Alaska
to capture and relocate enough otters to resurrect them on the B.C. coast.
It turned out to be a giant experiment on the entire west coast ecosystem.
In 1970, a coast guard ship was converted to transport a large number of otters
to the west coast of Vancouver Island.
[Voice Over] Sea otters were released in British Columbian waters.
This may not have been home, but home was never like this.
It's a remarkable conservation success, really when you think about it.
So sea otters were extirpated in British Columbia by the early 1900s.
[Reporter] In the past 50 years they've spread
from the 89 otters released there are now more than 8,000 on the B.C. coast.
Sea otters aren't unusual.
Just because they have such a huge appetite and the change is so immediate
and so direct, I mean it's night and day.
[Reporter] Vancouver Island university professor emeritus Jane Watson has been studying sea otters
for more than 30 years.
And was one of the first to document their profound impact.
No one was expecting it.
When sea otters were reintroduced no one knew that that they were going to change ecosystem.
[Reporter] What they also didn't know was how it would impact the multi-million dollar shellfish industry
and the diets of many coastal Indigenous people.
[Reporter] 98-year-old Kyuquot elder Hilda Hanson saw otters decimate clams, urchins
and other foods inside her community's traditional territory.
Something documented in a Simon Fraser University research project.
[Reporter] Indigenous leaders hadn't been consulted.
Scientists hadn't foreseen the impact of the otter's reintroduction on the food chain
but their return has an underwater upside.
This is what's known as a sea urchin barren
created when the urchin population explodes without otters to control them.
Urchins devoured once huge kelp forests
but now with otters returning scuba divers are seeing the kelp come back.
Marine naturalist and scuba diver Jackie Hildering specializes in photographing kelp.
The otters have done their work here.
Like I went down thinking I'll be back in a few minutes with an urchin
and like ridiculously all I could find is one urchin test of a green urchin.
[Reporter] Once the urchins are eaten by the returning otters, kelp quickly grows back.
It plays a vital role in the underwater web of life
sheltering all kinds of creatures
and kelp even sequesters large amounts of carbon which helps combat climate change.
All kinds of signs of reproduction happening down there.
Huge rose anemones.
I ended up in a school of juvenile herring.
So many juvenile rockfish.
Kelp greenling.
[Reporter] While Indigenous people had little say in the return of the sea otters
they're now adapting to the changes they're bringing.
All right.
So where are we?
We're at a place called X̱wa̱mdasbe'
So it means the place of otter and it's an old ancient village site.
Mike Willie is a hereditary chief from Kingcome Inlet
and also owns a wilderness tour company.
Boardwalk this whole place with tent platforms.
He's planning a high-end camping outpost for tourists paying a thousand dollars a night.
I'm excited about it.
It's bringing a new economy isn't it?
Sea otter viewing.
It's giving our First Nations a chance out here to take part in mainstream economy.
[Reporter] He grew up on the water
and sees a big difference between places that have sea otters and those that don't
such as his home community to the south.
You see the change.
It's different down there.
There's hardly any kelp forest down there but there's lots of life up here.
It's another world up here.
And the balance that the otters will bring right is yet to be seen.
There's a couple tiny pups in this group.
[Reporter] For thousands of years this coast was home to both sea otters and people.
The key now is finding a fresh balance.
Greg Rasmussen, CBC News, Hope Island, B.C.