Poor salmon run can be a disaster
Predators such as bald eagles and bears rely on the fish for survival
B.C.’s bald eagle population has already had a rough year, and it could turn into a catastrophic one if dire predictions about the fall salmon runs come true.
Scientists have warned that our hot and dry summer has caused unusually warm river temperatures, which means many fish could either avoid returning to their home waters to spawn, or die trying to make the journey.
Bald eagles depend upon the carcasses of spawned salmon to fill their bellies for six months of the year, according to wildlife biologist David Hancock.
“Are the salmon going to get up the rivers to spawn this year? That’s the question,” he said.
If they don’t, “The worry is that it will be devastating for eagles.”
Local eagles have experienced an above-average number of deaths and a significant number of failed nests this year.
Last week, 18 juvenile bald eagles were brought into the Orphaned Wildlife Rehabilitation Centre after they fell from their nests — the largest number the Delta facility has ever seen. Another five were found dead.
“This has been not a good, productive year for eagles,” Hancock said. “More nests fell down on us than we’ve ever had before.”
It’s hard to pinpoint the cause of the eagles’ problems, but it’s possible that some nests may have fallen from branches that died because of a lack of water. Contaminated food sources could also be to blame.
Whatever the reason, the impacts of a poor reproductive season would only be compounded by an inadequate salmon return.
“That would be catastrophic,” Hancock said.
And eagles aren’t the only organisms that depend on the salmon run for survival.
“It’s a whole host of other things that depend on the salmon carcasses. The whole ecology of the river is dependent on those nutrients going into the water and feeding insects, which are going to feed the next year’s salmon,” he said.
That ecology includes bigger animals like bears and wolves that also feed on salmon in the fall.
“It’s a huge energy source for them to put on fat before they go into winter dens or have to go through the winter like wolves,” Hancock said.
Bears could see other effects from the drought as well, according to UBC ecologist Wayne Goodey. If the current weather patterns continue, we may see them coming into inhabited areas more often.
“I’m sure there’ll be many more bears that’ll be coming here. The bears will be desperate for food if their natural areas are getting too dry to produce fruit,” he said.
“If it stays warm right through the autumn we’re going to have extremely late hibernation. And that could be an issue, too.”
So far though, the region’s bears have been behaving normally for this time of year, according to Christine Miller of the North Shore Bear Society.
On the flip side, some animals thrive in these conditions.
“It could be a massively positive impact for some things,” Goodey said.
Rats, for example, can always head into the sewer system for a drink if they’re thirsty. Any heavily water-dependent animals — things like frogs and salamanders — that die of dehydration will also provide a smorgasbord for those opportunistic scavengers.
Bees and hummingbirds, which feed on nectar, are also doing quite well right now.
“As long as it’s warm and dry, plants are going to be pumping out nectar like crazy because it’s the best time to be spreading pollen around,” Goodey said. “Of course, if it stays dry for too long, the flowers are going to shrivel up.”
He said he’s noticed a big increase in the Lower Mainland’s mosquito population, likely because those standing pools of water that remain are quite warm, providing optimum conditions for larvae to develop.