Canada’s Department of Fisheries and Oceans had projected that up to 11 million of the fish would return to spawn during August, but only about 600,000 have shown up so far.

A record number of the young salmon were born in 2005 and then swam out to sea in 2007 after maturing upstream. They were expected to begin returning to spawn this month.

First Nation tribes that depend on the salmon have expressed alarm over the missing fish.

Some marine biologists theorized that the young sockeye became infected with sea lice as they swam past fish farms around the mouth of the Fraser.

The parasites are known to accumulate around salmon farms, which often use chemicals to control the infestations.

Adult fish can survive the lice, but the parasites can easily attach and damage thin-skinned juveniles.

Another possible cause of the missing fish is the near-record warmth of the Fraser this summer. Federal salmon resource manager Jeff Grout told the Vancouver Sun that the current temperature of 68 degrees Fahrenheit can suppress the salmon’s normal maturation schedule for egg development.

He said that if the Fraser were to become any warmer, "it would be expected that the fish would simply stop migrating upstream and die."

Photo: Stock