The same warm summer weather that killed 1,000 King salmon two weeks ago in Blind Slough is also contributing to a larger than average presence of humpback whales in Frederick Sound.
Barry Bracken, retired whale tour guide and marine biologist, said the sunlight warming the sound produces a large phytoplankton bloom last spring.
“And that’s what started the chain reaction for the krill,” Bracken said.
Krill feed on phytoplankton. Because the plankton population increased, so did krill numbers. That string of events contributed to whales gorging themselves at the Frederick Sound all-you-can-eat buffet.
“Whales need to create blubber reserves for their long trip back to Hawaii,” Bracken said. “It’s about a 3,000 mile one-way trip and it takes a tremendous amount of energy to make that trip.”
The journey to Hawaii’s breeding grounds takes about a month where they live on the blubber reserves they stockpiled in Alaska and the females birth calves.
Bracken said the whales leave at different times but start thinning out in October.
Young and breeding age females go first followed by mature males and finally by mothers with calves. Pregnant females and mothers want to stay and feed as long as they can, leaving as late as January.
It’s a simple case of storing the most nutrients for the least amount of effort. Bracken said there probably aren’t more whales in Southeast Alaska, just more near Petersburg.There were fewer whales in the region last year, which could have also contributed to current increased krill populations.
Whale watchers are also reaping the rewards. Christine Thiel-Carruth, who was visiting Petersburg from Oregon, went on a whale watching tour August 2. She said she never expected to see so many whales in one place.
“There were whales where you would have two going through the same motion, like synchronized, but then we saw six doing the same thing,” Caruth said.
Bracken said, as of Saturday, August 3, the whales’ food source in Eastern Frederick Sound was still abundant.
“There was a dense layer of krill that varies from about 10-15 fathoms thick starting from about 30 to 50 fathoms down.”
From reports he’s heard, Bracken said there may be as many as 150 or more whales in Eastern Frederick Sound.
Scott Hursey, the Alaska Passages Charter operator, said he’s taking trips further out to places like Chatham Strait and earlier this summer the whales were concentrated there.
“But it changes every day,” Hursey says. “It’s a pretty good opportunity for whale watching closer to Petersburg than normal. We don’t know where they are day to day.”
He said they normally see this many whales but they tend to be more spread out and the humpbacks are more concentrated this year because of feed concentrations.