The highest number of coho salmon in a decade have returned to the Goldstream River, even though they left in 2011, the same year thousands of litres of fuel spilled into the river.
However, few of the returns have tags that were attached to fish released shortly before the spill, adding fuel to fears that any fish in the river at the time of the spill would have perished.
"The numbers are really encouraging for coho," said Peter McCully, Goldstream Hatchery technical adviser.
About 900 have been counted so far.
Returns are usually in the range of 75, but have occasionally risen to 500.
Other southern Vancouver Island rivers are also seeing promising early coho returns.
No one knows for certain why the returns are good this year, but there must have been favourable survival conditions in the ocean, McCully said.
"With our natural human arrogance we think we know what's going on and, every so often, Mother Nature gives us a quick kick in the pants," he said.
There are interesting changes in how the fish are behaving this year, McCully said.
"It looks like the run is earlier than usual. Normally we don't see them turning up in good numbers until November," he said.
"Some have also taken on their spawning colours. The coho we would normally get at this time of the year are bright silver.
"Something is changing," McCully said.
Although hatchery volunteers are delighted with the number of coho, the lack of tags is not good news for any fish that were in the river in April 2011, when a Columbia Fuels truck rolled over and spilled 43,000 litres of gasoline and 700 litres of diesel, much of which leaked into the river.
"When the spill occurred in 2011, we had started releasing our juveniles about three weeks before.
There were 8,000 released the day of the spill. Altogether, 34,000 were released prior to the spill," McCully said.
Most of those had clipped adipose fins and nose tags, but less than two per cent of the returns are tagged.
"It supports the worst fears that everything downstream of that spill was compromised," McCully said.
That could include steelhead and cutthroat trout as well as salmon.
The hatchery retained all juveniles that had not been released for an extra two months after the spill and released them once the water quality started to improve. Those fish were not tagged.
Chum salmon, which make up the famous Gold-stream run, are starting to come in to the lower reaches of the river, but the main mass is still in salt water, with the peak of the run expected between Nov. 12 to 14.
Chum affected by the spill will not return to Gold-stream until next year and the following year.
Columbia Fuels has spent more than $2 million on the spill cleanup and some fuel remains trapped under the highway and in the adjacent bedrock, according to the Environment Ministry.
In September, James Alan Smith of Nanaimo, driver of the truck, was handed a three-month conditional sentence, followed by nine months of probation after pleading guilty to dangerous driving and violating the Fisheries Act.