Federal and provincial officials say they're considering options such as trucking or helicoptering salmon upstream, as hundreds of fish remain trapped in a narrow area of the Fraser River Canyon, unable to migrate upstream and spawn following a rock slide.

The slide, which happened in a remote area just west of Clinton — about 100 kilometres northwest of Kamloops — has created a five-metre waterfall blocking salmon from passing through since late June. Seven hundred fish are known to have gone through as of last week, but it's unknown how many are pooled beneath the boulders.

On Tuesday, Doug Donaldson, B.C.'s minister of forests, lands, natural resource operations and rural development, and federal Fisheries Minister Jonathan Wilkinson toured the slide site in a helicopter to assess the damage.

Wilkinson, who previously called the situation his department's "top priority," said that while he'd been briefed on the situation before, it was a "sobering" experience to see the site first-hand.

"This is a very serious challenge. I don't want to underestimate or downplay the challenges that we face ... it's a very remote area, very steep cliffs, very, very turbulent water," he said.

The fish involved include chinook, steelhead, coho and sockeye.

Watch video of the helicopter tour surveying the blockage:

Video taken from a helicopter shows the extent of damage from a landslide near Big Bar, just north of Lillooet, B.C. 2:28

Wilkinson said the federal government, the province, and First Nations groups from up and down the river are working in tandem and are considering a number of options to help get the fish through. But each option has limitations.

Trucking the fish out would require building an entirely new road down the steep embankment, which Wilkinson said would present "a pretty big engineering challenge." Crews are also considering transporting the fish upstream by helicopter and releasing them from the air.

But that option would be costly and could only be used for a limited number of fish.

The best and least intrusive option, said Wilkinson, would be to manipulate the boulders in the river, creating natural pools that could help the fish migrate upstream.

Donaldson agreed, but said those efforts are hampered by the extremely high water levels that have already forced teams to remove acoustic monitoring equipment previously placed in the river to determine whether fish were getting past the slide.

On Tuesday a flood warning was issued for the Chilcotin river, north of the Fraser River slide location.

Fisheries and Oceans Canada originally said the slide happened on June 21 or 22, 2019. But federal Fisheries Minister Jonathan Wilkinson said it's now been established it happened "months ago." (Fisheries and Oceans Canada/Twitter)

"There was a lot of debris flow and the extra water in the river has made the obstruction even greater," Donaldson said. "It's an amazing amount of water flowing through a very narrow part of the Fraser Canyon.

"Salmon are an amazing species... but Mother Nature is an extremely powerful force."

For now, officials are hoping for a solution that won't involve aircraft or building new roads — that water levels will simply drop naturally, allowing fish to pass through and spawn.

'Very concerned'

The Fraser River is the most important salmon-bearing river in B.C. Even before the salmon became trapped by the boulders, they were already embattled.

Chinook salmon especially are considered endangered, and have already been the subject of a number of federal government protection plans because of their dwindling numbers.

"We are very concerned because if we cannot find pathways to get most of these fish through this will affect the cycle," Wilkinson said. "Every several years there will be holes in the salmon migration which will be a challenge for everyone who participates in the fishery, but not the least of which First Nations who rely on it for food."

While Fisheries and Oceans Canada originally said the slide happened on June 21 or 22, Wilkinson said it's now been established it happened months ago — but the implications for fish populations were not understood until recently.

"I will tell you that as soon as we were made aware of it we deployed people here the next day to try to figure out what was going on and we have worked very actively ever since then with all the resources to ensure that we're doing everything we can," he said.