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Harbor seals hauled out on rocks, San Juan Islands. Photo: Mick Thompson (CC BY-NC 2.0)

Do we know enough to do anything about all the seals and sea lions in Puget Sound?

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Scientists have known for years that Chinook salmon are important to southern resident orcas, but Chinook are not the only fish the whales eat. At the moment, chum salmon are returning to Puget Sound, and recent orca sightings suggest that the whales may now be feeding on chum.

Harbor seals also eat Chinook salmon, but also chum, coho and other fish. They seem fond of smaller fish like herring and juvenile salmon. Oh, what a tangled food web we weave… Can we really say that seals are stealing the lunch from killer whales?

Southern resident orcas are considered endangered. Puget Sound Chinook and steelhead are threatened. Harbor seals seem to be everywhere, hardly struggling to find food, at least as far as anyone can tell. So is it time to bring the powerful influence of humans into the equation by forcefully reducing the harbor seal population in Puget Sound?

Harbor seal skulls helped to reveal something about seal diets years ago.
Photo: Megan Feddern

It’s a question that people have been pondering for years, but I’m not sure we’re much closer to an answer. A new report, which I will discuss, offers some options for the Salish Sea.

Meanwhile, a recent permit will allow more than 700 salmon-eating sea lions to be killed on the Columbia River, but that has nothing to do with Puget Sound. Before addressing the problem of seals in the inland waterway, some key questions need to be answered, as discussed in a story I wrote last month for the Encyclopedia of Puget Sound.

Some of the most important questions surround how much salmon the seals are actually eating and how they fit into the complex food web that involves all kinds of fish and marine mammals. We can’t forget, for example, that transient killer whales eat a fair number of harbor seals, so it’s not a one-way street.

A recent study examined the bones from harbor seals that died years ago to determine if today’s seals are eating higher or lower on the food web. It’s a fascinating study involving stable isotopes from amino acids found in the bones. I believe I was able to explain simply enough the basic techniques. See Encyclopedia of Puget Sound, Sept. 8, 2020.

On the experimental front, a new acoustic device is being tested as a deterrence for harbor seals and California sea lions that have been feasting on threatened salmon and steelhead coming through the Ballard Locks on their way into Lake Washington.

Researcher Laura Bogaard of Oceans Initiative installs speakers used in a new experiment on harbor seals at the Ballard Locks. Photo: Laura Bogaard

The device mimics the sound of a killer whale slapping the water with its tail. The idea is to startle the fish-eating pinnipeds and move them away from the fish ladder, where they often pick off fish trying to make it over the dam. For details, listen to the story by KUOW reporter Eilis O’Neill, or check out the news release from Long Live the Kings, one of several organizations partnering in the project.

A new report released in September offers a list of actions that could be taken to reduce seal and sea lion predation in the Salish Sea. The technical report (PDF 4.4 mb) summarizes the discussions from a November workshop attended by 75 U.S. and Canadian experts.

Author M. Kurtis Trzcinski of the University of British Columbia divides the suggestions into four categories:

Vary hatchery production:

Salmon and steelhead hatcheries should experiment with releasing young fish all at once or over longer periods of time to see what is most effective at reducing seal predation. Larger releases might “flood the predator field” so that more of the fish get away. Fewer fish coming out of a hatchery at any one time might attract less attention and increase survival.

One could also change the release location to see if there are places where the hatchery fish have a better chance of surviving. One could also hold the fish for longer or shorter times in the hatchery to see whether larger fish survive better or worse than smaller ones.

Another idea related to hatcheries is to produce forage fish, such as herring, with the idea that an abundance of forage fish might provide an alternate prey for seals and sea lions, thus reducing predation on salmon.

A harbor seal catches a salmon at the Ballard Locks.
Photo: Laura Bogaard, Oceans Initiative

Enhance fish survival

Leaving aside seals and sea lions, these ideas relate to habitat efforts to increase survival of salmon and steelhead in the streams and estuaries. Improving stream flow and assuring proper temperatures could be critical factors, along with enhancing habitat for better food and protection for the growing fish.

Enhancing habitat to increase survival of other species, such as forage fish, could help with salmon and steelhead survival.

Non-lethal removal

Discouraging seals and sea lions from eating salmon and steelhead could take the form of harassment, removing or relocating haul-out areas, or requiring marinas to build structures to keep pinnipeds off docks and floats.

Harassment with noise or physical disruption could be scheduled at key times, such as during salmon out-migration or return to the streams. But workshop participants gave the idea a low chance of success.

Preventing seals from hauling out, especially near salmon migration routes, might work in one area, but it probably would move the animals to another location with uncertain effects.

Another idea was to inject the animals with a contraception to control the population, although a project involving the handling of thousands of seals and sea lions would be immense.

Lethal removal

Killing seals and sea lions could be accomplished through hunting, which would require the hunters to use the animal for food or other purposes, or culling, which means killing the animal for the sole purpose of reducing the population.

Some experts proposed running an experiment by reducing the population through culling and then measure the effects on fish populations. Others suggested removing all the seals in one area and comparing the effects to a similar area where seals were not removed.

Preliminary estimates say it would take the lethal removal of 50 percent of the harbor seals — or about 20,000 animals in the Salish Sea — to push Chinook and coho salmon toward recovery. In addition, about 3,000 animals would need to be killed every year to maintain a stable population.

Uncertainty of such actions is high. Some say that other predators might need to be removed as well to keep them from simply eating the fish saved by eliminating seals. Birds, otters, raccoons and large fish are among the predators that could become a concern.

Officials in both the U.S. and Canada are considering their next steps, including an action plan that would probably include research to improve our understanding of the food web.

Related articles from the Encyclopedia of Puget Sound:

2 comments

  1. Dan Ostlund says:

    Seals are smart, soon they WILL understand that the whale slapping machine is a hoax. Few people remember lessons learned by our recent past. Humphrey was a sea lion at the Ballard locks eating salmon by the hundreds… so the state finally decided to capture him and relocate him to California…this was the reasoning for the solution. Next thing you know, he was right back at the locks again.
    Killing seals in one area and not in another would simply result in the other seals relocating when there are more salmon and less seals. No common sense here.

    Our forefathers had to survive, they had to do what they had to do to live. One mistake could have cost them and their families lives… and they were smart, they had a long lost survival skill, common sense. As a 45 year sport fisherman in Puget Sound, and by the grace of God, I have been given some common sense, with no axe to grind…

    What about the starfish that are gone? What about the sea urchins that used to be on the pilings at point defiance, providing valuable nutrients to the bay? The seals have stripped every single piling. The pilings at point defiance are bare, no food for the starfish. They used to be totally covered a foot thick with wonderful sea anemones. What about the crabs? I am sure they would appreciate a seal to snack on every once and awhile. That wouldn’t be so bad would it?
    Culling? What about crab bate? We call it crab bait…Culling… that’s such a bad context to look at this. Unbelievable.

    I studied the northern pod of orcas from Telegraph Cove for over a year. They need nutrients, and salmon to live on, including hatchery salmon… come on, with all the proposed building permits, we will never get back to the way it was in the 1800’s. We need to wake up and stop using 80mm feasibly studies to pad the pockets of researchers….

    This is ‘word from the street.’

    My great grandfather settled in Tacoma in 1898 from Sweden. I have watched the Puget Sound fishing situation for my whole life.
    I remember the fishing stories of my uncles. I am a fisherman, I do not hunt animals. Never have and never will. Would break my heart to kill an innocent animal… unless there was an excellent reason to do so. We have an excellent reason to farm seals and sea lions. There are simply way too many of them. They are so cute… that is the problem.. they go on un-checked.

    A few years ago I went fishing a long time manager of point defiance boathouse. He is very active in all of this but we all feel, nobody cares… nobody listens… our solutions do not create revenue, so we are nobody… it is too bad. We do not create 80mm feasibility studies.
    If ordinary people, the mom and the pops, really knew, from experience, not from textbook, what was going on, if they understood the solutions to the problems, we all would have better lives with a thriving Puget Sound.

    The solution from all of us sport fisherman on how to make Puget sound flourish again? (Forgive me for repeating myself here).

    1. Reopen all closed salmon hatcheries in Puget Sound. Produce hatchery salmon. ( native salmon would flourish again in no time )
    2. Manage our sport fishing and give us more opportunities to catch salmon from private boats. (So much more $$$ for the state).
    3. Harvest the seals and sea lions. In the 1970’s, we would get $4.00 for every ear we brought into the marina. Guess what? It worked. Harvesting works. Do it at night, hire the military, put the solution before feelings…there are WAY too many seals and sea lions and it doesn’t have to take tens of millions of dollars and many years to solve. They are eating all the salmon. Figure it out, keep it simple.
    4. More hatcheries=more salmon. Less seals = more salmon (and a restoration of sea urchins on our pilings and kelp beds and starfish and crab food). More salmon = more orcas.
    Less seals = More beaches to enjoy (go to eagle island and you will see almost 1/2 the island layered with seals on any given morning).

    5. Again… the solution is more salmon, right? And a restoration of our waters.
    6. More hatcheries = more salmon (including native), Less seals and sea lions = more salmon (sea urchins etc), more salmon = more Orcas. More orcas and we are all happy.
    7. Also, we have no more rock cod or ling cod. Why? Loss of habitat. The old Narrows bridge on the bottom of the bay is gone. It has deteriorated by the currents over time. That’s where the cod used to live. Replace the habitat. Cod will return. We all say…. Sink a few old ships at night that have been stripped down to pure metal in the narrows… octopus would thrive again too.
    8. Summary… re open the salmon hatcheries you closed down, farm the sea lions, sink a bunch of ships in the narrows, open the sport fishing industry again and make your millions there, and we would restore the Puget Sound the way it was 100 years ago. It sure would be nice to see a starfish again… don’t you think?

    This is the consensus of experienced Puget Sound boaters, who love nature, pure water, and simple thriving sea life.
    Just a little common sense is all it would take. Unfortunately, a lost commodity for many decision makers today.

    You have my permission to use bits and pieces of my thoughts…. If there is something I am incorrect on, or something
    I am missing, please let me know. Thank you and thank for creating this blog.

    • Dan, I can’t help but admire the free flow of ideas. It’s almost like poetry, a mix of nostalgia, memories and fervor. “More hatcheries=more salmon.” Who can argue with that? And who could possibly believe that the ecosystem is complicated?

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