The Canadian government projected that between six and 10 million sockeye salmon would return to thethis month.
But the official count for the annual 'summer run' -- by far the largest of four salmon migrations that see millions of fish return to Canada's lakes and rivers from the Pacific each year from June to late August -- is now just 600,000.
Where the others went remains a mystery.
Local fishermen, described the situation as "shocking," a "catastrophe" and a "crisis," while public broadcaster CBC said 2009 could end up being the worst year ever for the industry.
A record number of salmon smolts were born in the Fraser in 2005 and migrated to the ocean. Nature dictates that most of them should have returned by now to spawn.
"It's a bit of a mystery," Stan Proboszcz, an expert fish biologist from the Watershed Watch Salmon Society.
"Honestly, we don't know what happens to them when they go out into the ocean," he said. "There's a myriad of factors that could explain what's going on." It is "quite shocking," he added.
Officials and ecologists speculated the salmon which are extremely temperature sensitive could have been affected by warmer ocean temperatures, fewer food sources, or juvenile salmon may have contracted sea lice or other infections from some 30 fish farms in the Strait of Georgia as they migrated out to sea.
Proboszcz, however, suggested that fishing industry officials may have miscalculated their complex forecasts or that the fish could just be late arriving -- although he conceded the latter theory was highly unlikely.
Wild salmon are under threat in many rivers of the north Pacific and north Atlantic because of at sea.
Environmental groups in Canada, Norway and Scotland have been fierce critics of salmon farms because of fears over sea lice -- naturally occurring parasites of wild salmon that latch onto the fishes' skin in the open ocean.
Salmon farms are a haven for these parasites, which adult salmon can survive but which small, thin-skinned juveniles are vulnerable to, especially when heading from the river to the sea.
Department of Fisheries and Oceans spokeswoman Lara Sloan said the main Fraser river fishery had not opened due to the drop in numbers and that another local fishery had scaled back this season's catch to just five percent of the norm. No recreational fishing has been allowed.
Sloan would not be drawn on the reason behind the lack of fish.
"There are a lot of variations in the ocean," she said. "They're all interconnected, so it's impossible to point to one reason for this happening.
"So far, they're not coming back in the numbers we expected, but we will continue to look for them."
Other species,and , are due to arrive around the end of August through October. So far there is no indication they have been affected.
are also returning to spawn in the region, but they have been a "conservation concern" for several years, and their numbers remain low.