Clumsy On Land, Seals Are Superb Athletes Underwater. According To The Nonprofit Seadoc Society, Harbor Seals Can Dive 600 Feet
On a recent morning, after some acrobatics and horsing around, a seal cruising the locks suddenly took an all-business turn. When it resurfaced, it was with a mouth crammed full of coho. The Hiram Chittenden Locks, built more than 100 years ago, allow navigable access from the freshwater of Lake Washington and Lake Union to Puget Sound. But the locks also inadvertently created an attraction for seals.
The concrete chute of the locks concentrates salmon, making easy pickings.
As salmon runs have declined in Puget Sound, a range of methods has been tried over the years to shut down the buffet. Underwater firecrackers, pingers — even Fake Willy, a faux orca that used to be lowered into the channel in an attempt to scare off seals and sea lions.
Now a new gadget is being tested at the locks, intended to startle seals to deter them.
The so-called Targeted Acoustic Startle Technology, developed by scientists from the Sea Mammal Research Unit at the University of St. Andrews, is marketed by GenusWave Ltd. based in Edinburgh, Scotland. The device was made for use at fish farms, to keep seals away from net pens.
The device is housed in a metal canister that looks like an upscale water bottle, and produces a sound played through two underwater speakers at randomized intervals. The sound it makes is not particularly loud or unpleasant … to a person. But to a seal?
“You wouldn’t think it’s a big deal,” said biologist Laura Bogaard, who helped with the trial of the device at the locks this summer byOceans Initiative, a Seattle-based research nonprofit. “But it’s my sense the seals spend more time further away when it is on, and when it is off, they are closer.”
The acoustic technology replaces conventional, loud noisemakers that seals just get used to. The sound made by the startle device provokes a flight response — a fundamental mammalian reflex — without causing harm to the seal, or bothering salmon.
Partners in the experiment include the U.S. Army Corps of Engineers, the state Puget Sound Partnership, the Muckleshoot Indian Tribe, the Suquamish Tribe and nonprofit Long Live the Kings.
If the device works, it could help ease a frustrating and highly visible problem for salmon managers.
Adult coho salmon could be seen milling near the concrete sides of the locks, gray ghosts sliding through the deep green water.
“You think of all the things they have done, and survived to get here,” said Erin Ashe, executive director and research scientist with Ocean Initiative, watching the salmon in the depths.
These coho made it to sea as juveniles, survived to fatten and grow in the vast ocean, escaped fisheries in Alaska and Puget Sound to return — via a circuitous route through the locks — to get this far. Only to be nailed in a concrete slot by the seal just waiting for them.
“They get hammered by a harbor seal any self-respecting salmon could escape in the open ocean,” said Rob Williams, chief scientist for Oceans Initiative. “There is something underdoggy about the whole thing.”
Researchers have long known seals munching both juvenile and adult chinook, coho and steelhead are taking a bite out of salmon recovery in Puget Sound.
The Washington Department of Fish and Wildlife has estimated that Puget Sound harbor seals eat lots of juvenile chinook salmon — between 5.2 and 26 million smolts in 2016, based on samples of seal scat and other information.
Chinook comprised only 1% to 2% of the diet that year between the months of February and August, the WDFW estimated.
It was just a one-year study, with a lot of uncertainties in a complicated ecology and food web. But researches estimated even that small percentage multiplied across the estimated 19,000 harbor seals in the inland waters of Puget Sound could translate to 84,000 to 167,000 fewer adult chinook returning.
It’s not that seals are a new or exotic predator. It’s rather that the balance of so much has shifted in Puget Sound, tipping the advantage to the seals in a highly altered environment the seals can exploit.
Seals are the homebodies of Puget Sound. Year-round residents, they are the water body’s most common marine mammal, and harbor seal populations are healthy.
Clumsy on land, seals are superb athletes underwater. According to the nonprofit SeaDoc Society, harbor seals can dive 600 feet, and remain underwater 30 minutes at a stretch, lowering their heartbeat and taking oxygen from their blood and muscles. They can live in fresh or salt water, and seldom stray more than 5 miles from where they were born.
Descended from the same family of ancestors as dogs and bears, with their big eyes seals can see in dark waters they probe with whiskers sensitive enough to detect pressure waves from passing fish.
Seals eat a varied diet. In the 2016 study, the WDFW documented that seals consumed 57 varieties of prey, including 53 species of fish.
Fishermen have long fingered seals as competitors for salmon, and the WDFW used to pay a bounty for every seal nose sent to Olympia.
That stopped with the passage of the federal Marine Mammal Protection Act. With hunting and harassment of marine mammals banned since 1972, Washington’s marine waters today are boiling with life: more humpbacks, gray whales, porpoises, dolphins, sea lions, minke whales and killer whales — except for the southern resident orcas.
The southern residents face three main challenges: boat noise and vessel disturbance, pollution and lack of chinook, their primary prey.
The success today of marine mammal recovery could be complicating efforts to rebuild the endangered population of Puget Sound’s southern residents. Consumption of chinook by protected marine mammals other than southern-resident killer whales jumped 150% from 1975 to 2015, researchers stated in a 2017 paper.
Boosting chinook populations would provide more food for endangered southern resident killer whales, as well as more than 100 other species of animals that feed on salmon — in addition to providing better opportunity for fishermen.
On the Columbia River, salmon managers enforce a death penalty to deal with salmon predation by native wildlife that has figured out how to exploit human alterations of the river.
The U.S. Army Corps of Engineers hired federal contractors to kill thousands of double-crested cormorants in the Lower Columbia River resulting in the collapse in 2017 of what had been the world’s largest cormorant colony. Last August, the National Oceanic and Atmospheric Administration approved a kill program on sea lions, targeting up to 716 sea lions over five years in 200 miles of the Columbia River to reduce predation on salmon at the dams.
At the locks, the noisemaker is a nonviolent solution to a small problem in the much larger conundrum of salmon and orca recovery.
Seals are an easy scapegoat to target in the decline of both salmon and southern resident orcas, especially when they’re seen ripping salmon apart right in front of people.
But chinook salmon the southern resident orcas depend on are declining overall because of a variety of problems that will take a lot more than just shooting seals and pumping out more hatchery fish to fix.
Warming ocean temperatures are altering salmon food webs. Climate warming also is altering stream flows and heating summer river temperatures. A deluge of hatchery fish; destruction of stream and estuary habitat; fishing pressure and pollution all have put chinook at risk of extinction from the Fraser River of British Columbia to Puget Sound to the Columbia and Sacramento rivers.
But if the noisemaker works, it could be tried elsewhere in Puget Sound, and maybe even in the Columbia. Would it work on sea lions? That hasn’t yet been tested, but the Oceans Initiative team has moved the device to a Bellingham area hatchery, for another round of experimentation on seals.
Williams has no illusions the noisemaker solves the demise of salmon and orca. But in an extinction crisis caused by a thousand cuts, perhaps this could be one more thing that helps.
“What we have always thought is if we could each give a little, scrape together a bit more salmon where we are losing them, that’s a start,” Williams said.
This news was originally published at chronline.com