Tag Archives: northwest fisheries science center

Competition For Chinook By Seals, Sea Lions Limiting Salish Sea Orca Recovery, Study Says

Despite decreasing Chinook catches over recent decades, runs haven’t increased overall and more new research is pointing the finger at the bellies of growing West Coast marine mammal populations, a hunger that may be “masking” salmon recovery efforts.

A study out today says that between 1975 and 2015, sea lion, harbor seal and killer whale appetites for the nutrient-rich salmon more than doubled, growing from 6,100 metric tons annually to 15,200 metric tons, or 33,510,264 pounds.

HUGH ALLEN SNAPPED THIS HARBOR SEAL STEALING A SAN JUANS SALMON LITERALLY OFF AN ANGLER’S LINE. (HUGH ALLEN)

That’s the equivalent of 31.5 million kings, up from 5 million 40 years ago.

 

The study was published by researchers from Oregon State University, NOAA’s Northwest Fisheries Science Center and WDFW and tribal biologists, among others, in the journal Physical Reports under the headline “Competing tradeoffs between increasing marine mammal predation and fisheries harvest of Chinook salmon.”

The rub is that the fish and finned mammals are both protected by federal laws.

While killer whales account for the lion’s share of Chinook poundage consumed — especially those packs that haunt the waters from the west coast of Vancouver Island north to the Gulf of Alaska — the study suggests that the increasing numbers of pinnipeds are impacting the ability of Puget Sound’s orcas to recover more so than our fishing seasons targeting kings.

“Our results suggest that at least in recent years competition with other marine mammals is a more important factor limiting the growth of this endangered population than competition with human fisheries,” researchers state.

Pinnipeds are infamous for stealing Chinook off anglers’ lines, but much of what they eat are actually juvenile fish — harbor seals in particular.

Those in the Salish Sea, which includes Puget Sound and the Straits of Juan de Fuca and Georgia, consume 86.4 percent of all those smolts eaten by marine mammals, “due to large increases in the harbor seal abundance in this region between 1975 and 2015 (8,600 to 77,800).”

“For Salish Sea Chinook salmon, strong increases in predation greatly exceed harvest; this is driven largely by local increases in pinniped abundance in the Salish Sea,” researchers write.

Overall, West Coast recreational and commercial catches have declined from 3.6 million to 2.1 million kings, while marine mammal consumption of adult salmon has risen from 1.3 million to 3.1 million.

Hatchery production peaked around 1985 at 350 million but has since declined to around 225 million a year. Overall hatchery and wild production is running between 400 million and 475 million in recent years, according to the study.

“… (L)ong term reductions in the salmon available for commercial and recreational fisheries may not reflect lower abundance of salmon, but rather a reallocation from human harvest to marine mammal consumption,” the authors write. “Because many populations of Chinook salmon in the Northeast Pacific are of conservation concern, substantial resources have been invested to improve salmon passage through hydropower dams, restore salmon habitat, reduce fishing, and otherwise improve conditions in rivers and streams to improve productivity. Collectively, these recovery efforts may have increased Chinook salmon survival or recovery, but these increases in salmon populations may be offset by salmon consumption by more-rapidly increasing populations of marine mammals and other predators.”

Columbia Basin fishery managers and others are pushing to increase lethal removals of sea lions, including most recently at Willamette Falls.

The new study, which looks at ocean impacts, found that for Chinook stocks from the Columbia south, “predation impacts have increased strongly over time and exceeded harvest in recent years.”

The Bioturbations Of Sand Shrimp: Not Just Bait, Important For Bays Too

Word of the day: bioturbating.

That’s what sand aka ghost shrimp and blue mud shrimp are doing in their little burrows in estuaries up and down the Northwest Coast 24/7/365.

Bioturbating the holy hell out of all that mud and silt and decaying plant matter and whatnot that collects on the tideflats, making it that much richer.

A RESEARCHER STANDS ON A TIDEFLAT PINHOLED WITH THE BURROWS OF SAND SHRIMP. AS MANY AS 600 CAN EXIST IN A SQUARE METER. (OREGON STATE UNIVERSITY)

All that free labor’s great for the health of the ecosystems our salmon and other critters depend on. By one estimate, burrowing shrimp filter as much as 80 percent of the water in bays.

And here you thought sand skrimps just existed to adorn a 2/0 hook with some eggs on the side!

A DIVER-AND-BAIT SET-UP RIGGED WITH A SPIN-N-GLO AND SAND SHRIMP. (ANDY SCHNEIDER)

But it’s not so good if you’re an oyster in Nahcotta or Newport. All that mucking around kills the valuable shellfish, which are hugely important for coastal economies. The oysters can sink into veritable “quicksand,” quickly suffocate and die.

So in effect, the shrimp have become the northern pikeminnows of our rich bays, a native species that has to be controlled so other more financially and culturally desirable ones may thrive in the altered environments.

AS OYSTERS MATURE THEY MUST REMAIN ON THE SURFACE OF TIDEFLATS, BUT WHEN THEY SHARE SPACE WITH BURROWING SHRIMP, THEY CAN SUFFOCATE AND DIE BY SINKING INTO THE MUD. (USDA-ARS)

In Washington pesticides have been used to kill them off, but that’s caused a big stir in recent years. A state permit to use imidacloprid was issued in 2015 but then almost immediately withdrawn at the request of the oyster industry after public outcry.

A subsequently “reduced scope” application for a five-year permit to annually spray up to 500 acres of Willapa Bay and Grays Harbor by hand and boat instead of helicopter is now out for public comment.

I have to admit that when I learned about the spraying, it really, really bugged me.

It wasn’t so much the self-righteous indignation of Seattle chefs, more like, should we be using that stuff in the environment, let alone to kill off key actors in it?

SAND SHRIMP. (THERESA HOGUE, OREGON STATE UNIVERSITY)

On the flip side, in a Seattle Times video, you can hear the frustration voiced by a Washington State University extension agent tasked with helping oyster growers figure out a different solution.

“We beat our heads against the wall,” says Kim Patten, “and nobody has come up with any ideas. So at this point I have no idea, and I don’t think anybody else does.”

Someone might, however.

A recently posted blog by the Northwest Fisheries Science Center on these “estuarine engineers” details research into figuring out where they do well in the bay, in essence attempting to learn if it’s possible to reverse engineer things to benefit shrimp and farmers.

“If it’s an area where we would anticipate the population going down, having weak reproduction, or growing slowly—perhaps, for aquaculture, that would be a good location, because you’d minimize the interaction between the shrimp and the oysters,” Dr. Katelyn Bosley of the Oregon State University’s Hatfield Marine Science Center, a stone’s throw or two from Yaquina Bay, told author Al Brown.

“Or conversely, you’ll identify areas where there are fast-growing shrimp because of the high-quality, high-food environment,” she added. “Clearly, by assessing the nutritional status of the environment and knowing that shrimp live there—maybe that’s not a good place to grow juvenile oysters at certain times.”

These are the kind of solutions we should be finding.

It’s also important because burrowing shrimp, particularly blue muds, are being wiped out by an invasive isopod carried here in ship ballast that turns them into zombies that can’t breed.

Usually stopping zombies from breeding is a good thing, but it’s unclear what happens if the shrimp disappear for good — it’s possible systems will become overloaded with nutrients and experience algae blooms, posits Bosley .

With how important the shrimp are — “a key part of their environments,” writes Brown — we should be looking for ways to keep them healthy instead — and bioturbating the bays.

PLASTER CASTS OF SAND SHRIMP AND BLUE MUD SHRIMP BURROWS. THEY CAN DIG AS MUCH AS A METER BELOW THE SURFACE! (USDA-ARS)