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Sea Lions, Other Marine Mammals Discovering South Sound Anchovy Boom

A large suite of marine mammals has discovered Deep South Sound’s new bounty of anchovies, schools of which are now so numerous they’re routinely observed during regular aerial surveys.

For three months this past winter, WDFW biologist Steve Jeffries observed hundreds of California sea lions, as well as harbor seals, harbor porpoises and long-beaked common dolphins feeding on a massive pod of the skinny, silvery baitfish in Case Inlet north of Olympia.

IN THIS SCREEN SHOT OF AN IMAGE FROM THE DEPARTMENT OF ECOLOGY’S JUNE EYES OVER PUGET SOUND REPORT, MARINE MAMMALS INCLUDE CALIFORNIA SEA LIONS SWIM IN A SOUTH PUGET SOUND INLET WHERE THEY FEED ON HUGE SCHOOLS OF ANCHOVIES. (COURTESY D.O.E.)

Anchovy populations have boomed in these waters since 2015 and the Blob’s warm waters.

What’s more, the pinnipeds and cetaceans appeared to be teaming up on them.

Jeffries says he would watch them forage in a 3/4-mile-wide by 3-mile-long oval from Herron Island up to Hartstine Point south to McMicken Island.

From his boat he could only guess at what was going on under the glass-calm surface, but it’s possible that as the sea lions and dolphins slashed through the anchovies, the other marine mammals waited close by to pick off stunned fish, he says.

“You wouldn’t even know they were there for four to six minutes. Everybody would be down,” Jeffries recalls.

As the sea lions swim along on top, the surface boils with them, a video taken by a Department of Ecology aerial photographer shows.

To double check what they were feeding on, Jeffries says biologists “scooped poop” and jigged the depths, reconfirming anchovies were on the menu.

Sea lions have another tactic as well.

“It looked to us like they pushed the bait into the cove; basically, they cornered them,” he said of another instance in Carr Inlet.

That can also lead to die-offs as the sheer volume of fish can “create a localized, low-oxygen event,” which may have been to blame when a bunch turned up dead in May 2018 in Liberty Bay near Poulsbo.

In one South Sound beach seine net set, scientists caught a staggering 250,000 anchovies in 2017.

ANCHOVIES CAUGHT IN A BEACH SEINE IN OCTOBER 2017. (PHILLIP DIONNE, WDFW)

High tidal fluctuations can also strand the fish as the water recedes.

The feast on the salty fish ended in March when another marine mammal discovered the sated sea lions — 25 transient orcas that sailed through the Tacoma Narrows to Case Inlet.

Transients are the ones that nosh on sea lions and seals; weaker-jawed southern resident killer whales only eat softer salmon and steelhead primarily.

SO WHAT DOES THIS EXPLOSION of anchovies mean?

“I think it bodes well for salmon in the future,” says Jeffries. “Marine mammals are not the only ones that eat anchovies.”

He suggests that anglers also might switch to lures that look like the skinny, 3-inch-long baitfish.

“Put an anchovy-mimic fly on,” Jeffries says.

ANCHOVY HAVE OCCURRED INTERMITTENTLY IN PUGET SOUND OVER THE DECADES AND ARE NOW IN THE BOOM PART OF THEIR POPULATION CYCLE. (PHILLIP DIONNE, WDFW)

Pinnipeds are drawing the ire of fishermen as studies show that they’re intercepting outmigrating smolts, which has been highlighted in part by spring’s Survive the Sound online challenge, not to mention returning adult salmon and steelhead.

As WDFW’s point man on sea lions Jeffries finds himself in the thick of that debate, so I asked him if this all might lead to “prey switching.”

“If you were a sea lion, would you chase one (salmon or steelhead) smolt or a school?” he asked me in return.

Based on Jeffries’ counts of 150 to 250 sea lions in Case Inlet over a three-month period and the needs of the 350- to 700-pound animals to eat 5 to 7 percent of their body weight each day to sustain themselves, WDFW forage fish researcher Phillip Dionne came up with a back-of-the-envelope estimate that they consumed between 118 tons to 551 tons, with a midpoint of 283 tons, more than half a million pounds.

“… Assuming they were only eating anchovy, the sea lions may have eaten more biomass of anchovy in three months than our estimate of spawning biomass of herring (south of the Tacoma Narrows bridge) was for 2018 spawning season,” says Dionne.

Jeffries says anchovies represent “an alternate prey source” that’s in high abundance.

A paper published in the journal Deep Sea Research Part II in January notes that survival rates on acoustically tagged winter steelhead smolts leaving the nearby Nisqually River jumped from 6 to 38 percent between 2014 and 2016.

“Predation buffering by abundant anchovy is one hypothesis to explain this change,” it states.

THE DEPARTMENT OF ECOLOGY’S LATEST EYES OVER PUGET SOUND REPORT SHOWS NUMEROUS SCHOOLS OF FISH IN MARINE AREA 13, LIKELY ANCHOVIES. (COURTESY D.O.E.)

ANCHOVIES HAVE BEEN INTERMITTENTLY ABUNDANT over the past century and a half, according to the paper, which looked at their historical fluctuations.

They apparently appeared in big numbers in the late 1890s — “they could be dipped up with a common water bucket” in a Port Townsend bay and were recorded as such in the late 1920s, late 1960s, mid-1980s, 2005, and again since 2015.

In the deeper past, “anchovy were the third most abundant fish in First Nations archaeological sites up to 3000 years old” in Burrard Inlet, on which Vancouver, B.C., sits.

It’s hard to say how long this latest anchovy boom will continue or how fast it may fade away and bust like in the past.

Though salmon and steelhead prefer cooler water, WDFW’s Dionne says that if warmer water sticks around, it could last longer than past ones.

While we yearn for clear-cut answers, that’s not the nature of Mother Nature.

“It’s difficult to say if this is going to be a good thing or a bad thing,” Dionne says. “California sea lions certainly love it.”