harbor seals

Tag: harbor seals

Minor bridge modifications could help young steelhead escape from Hood Canal

Help could be on the way for migrating steelhead and salmon in Hood Canal, where many young fish are killed each year by seals and other predators that lie in wait at the Hood Canal floating bridge.
As many as 50 percent of the steelhead migrants perish as they arrive at the bridge, where predators pick them off one by one. The bridge is supported by floating concrete pontoons, forming a nearly solid barrier across the waterway. Young steelhead generally swim near the surface, making them especially vulnerable to predation, although some fish will dive under the bridge to get to the other side.

Concrete pontoons can obstruct and slow the migration of steelhead.
Image: Jenny Paulo for Long Live the Kings

Engineers are currently designing minor modifications to a few bridge pontoons to help the fish find their way through existing gaps in the structure — one at each end of the line of floating pontoons. Those are the places where the bridge connects to the shore, and a small truss bridge carries traffic over the span.
I first learned about problems caused by the Hood Canal bridge in 2013, when researchers with the National Oceanic and Atmospheric Administration were able to track steelhead using tiny implanted transmitters (Kitsap Sun, Oct. 13, 2014).
The researchers could track the movements of the implanted fish using receivers placed throughout Hood Canal. For many fish, their journey ended when they reached the bridge, as indicated by following their tracks recorded on receivers at the bridge. When a fish was eaten, the transmitter — now in the belly of a seal, sea lion or bird — would suddenly show a completely different travel pattern. After the fish was digested by a seal, for example, researchers might determine that an immobile transmitter was among the excrement at the bottom of Hood Canal. (See the research article led by Megan Moore in the journal PLOS One.)
Further studies showed that the movement of young steelhead — and perhaps some species of salmon — were influenced by shifting currents around the bridge. Fish would often move laterally along the bridge structure until caught in eddies formed by tidal currents through the bridge openings. Larger numbers of fish were found in those eddies.

For a more complete understanding of these findings, please check out the recently released technical report compiled by Long Live the Kings, which coordinated the recent studies, or read an illustrated summary of that report. (Full disclosure: I wrote the summary text under contract with LLTC.)
As you will see in those reports, short-term solutions involve small structures that could be attached to the bridge to reduce the eddies and hopefully move the fish more quickly along the bridge and through the existing openings in the pontoons.
According to Lucas Hall of Long Live the Kings, the goal now is to get people to understand the problem and recognize the need for a temporary solution. Designs for the bridge modifications are already under way using existing grants.
An additional $2.5 million is needed to fabricate the attachments to the bridge and begin a monitoring effort as early as 2022. Full monitoring and further modifications to improve performance could cost another $1.5 million, according to current estimates.
While that might seem like a lot of money, the benefits to salmon and steelhead could be enormous, especially when one considers all the efforts that have gone into saving Puget Sound Chinook, Hood Canal summer chum and Puget Sound steelhead — all listed as threatened in Hood Canal and likely affected by the bridge in one way or another.
Harbor seals commonly haul out on Sisters Rock, about half a mile southwest of the bridge.
Photo: Hans Daubenberger, Port Gamble S’Klallam Tribe

Millions of dollars have been spent to replace culverts to improve salmon migration in the streams, not to mention improvements to freshwater rearing habitat. But those improvements are not fully realized when the young fish, after surviving many threats in freshwater, don’t live long enough to get out of Hood Canal.
“In comparison to the investments we are making in the fish-passage arena, this (bridge mitigation) would be immensely efficient and would be a huge win,” Lucas told me.
Eventually, the Hood Canal bridge will need to be replaced, and it now seems obvious that a different configuration for the floating pontoons would allow for increased fish passage with less risk. Gaps between each pontoon would be a major improvement, even if the pontoons extended well beyond the bridge. Perhaps before full bridge replacement, that kind of alteration could be considered for one or more sections of the bridge.
Photo: Hans Daubenberger, Port Gamble S’Klallam Tribe

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

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:

A harbor seal hunting anchovies. From Howe Sound Ballet video by Bob Turner: https://youtu.be/Ycx1hvrPAqc

Could anchovies and other fish take pressure off salmon and steelhead?

A recent influx of anchovies into Puget Sound may have saved some steelhead from predators, but researchers seek more evidence to prove the connection. Our series on the Salish Sea Marine Survival Project continues with a look at these and other potential impacts from predators on the region’s salmon and steelhead.
Read the story in Salish Sea Currents

Harbor Seals sunning on intertidal rocks of Puget Sound. Photo: Tony Cyphert (CC BY-NC-ND 2.0) https://www.flickr.com/photos/tony717/14630242564

Study would explore changes to protections for seals and sea lions

As wildlife managers work to recover Puget Sound’s diminished Chinook population, a proposed white paper is expected to review the impacts of some of the salmon’s chief predators. The study would include a section on potential management of seals and sea lions, prompting open discussion of a long taboo subject: Could officials seek to revise the Marine Mammal Protection Act — or even conduct lethal or non-lethal removal of seals and sea lions in some cases? Such actions are hypothetical, but we look at some of the ongoing discussions around the issue as prompted by a new resolution from the Puget Sound Leadership Council.
Read the story in Salish Sea Currents.

Seals and sea lions may be slowing salmon recovery, hurting orcas

A young resident killer whale chases a chinook salmon in the Salish Sea near San Juan Island, WA. Sept 2017. Image obtained under NMFS permit #19091. Photo by John Durban (NOAA Fisheries/Southwest Fisheries Science Center), Holly Fearnbach (SR3: SeaLife Response, Rehabilitation and Research) and Lance Barrett-Lennard (Vancouver Aquarium’s Coastal Ocean Research Institute). (CC BY-SA 2.0) https://flic.kr/p/21wV8rV
A young resident killer whale chases a chinook salmon in the Salish Sea near San Juan Island, WA. Sept 2017. Photo by John Durban (NOAA Fisheries/Southwest Fisheries Science Center), Holly Fearnbach (SR3: SeaLife Response, Rehabilitation and Research) and Lance Barrett-Lennard (Vancouver Aquarium’s Coastal Ocean Research Institute). (CC BY-SA 2.0) https://flic.kr/p/21wV8rV

Increased consumption of Chinook salmon by seals and sea lions in the Salish Sea “could be masking the success of coastwide salmon recovery efforts,” according to a new study published this week in the journal Scientific Reports. Endangered resident orcas are said to be declining in part due to a lack of available Chinook, the orcas’ preferred prey.
Read the article by PSI senior writer Christopher Dunagan in Salish Sea Currents.

Study of seals and sea lions gains interest

Seal vs Salmon. West End, Vancouver, BC. Photo: cesareb (CC BY-NC 2.0) https://www.flickr.com/photos/cesareb/8620647452
Seal vs Salmon. West End, Vancouver, BC. Photo: cesareb (CC BY-NC 2.0) https://www.flickr.com/photos/cesareb/8620647452

Our story last week about the impacts of predators on Chinook salmon populations in Puget Sound continues to gather strong interest from our readers. Several thousand viewed it after it came out last Thursday, and it was reprinted in the Kitsap Sun on Monday.
The story was written by PSI senior writer Christopher Dunagan and reports on a new study showing that area seals and sea lions are eating a much higher amount of threatened Chinook than previously known. Many questions still remain, but it is the first time that a peer-reviewed study has attempted to quantify these predator impacts to such a degree and in such detail.
Here are a few highlights: As many as one in five young Chinook are eaten before they can make it out of Puget Sound into the open ocean. Area seals and sea lions eat twice the amount of Chinook as do Puget Sound’s endangered orcas, and six times the annual commercial and recreational catches from local fishermen combined. Scientists attribute the large numbers to an increase in seals and sea lions since the 1970s after the animals were protected under the Marine Mammal Protection Act.
Not surprisingly, scientists and policymakers will have to look more closely at these numbers to determine what to do. Seals and sea lions are rightly protected, and old (and undesirable) policies of hunting the animals to protect salmon are not an option. Scientists say that even if such policies were possible, there is no saying that they would actually protect the salmon population.
The fact is that the seals and sea lions are just doing what they do naturally, and while their populations are healthy, there aren’t necessarily more of them than there should be. Some would argue that this study is a reminder that we need to continue to recover habitat and create better conditions for the salmon to withstand what are essentially normal pressures from the environment. Historically, Puget Sound’s Chinook and predators co-existed just fine, but that was before millions of humans started destroying the local streams and floodplains, degrading beaches and polluting the water. See a harbor seal with a salmon in its mouth? That can also be seen as a sign of Puget Sound’s health.

Study of seals and sea lions gains interest

Seal vs Salmon. West End, Vancouver, BC. Photo: cesareb (CC BY-NC 2.0) https://www.flickr.com/photos/cesareb/8620647452
Seal vs Salmon. West End, Vancouver, BC. Photo: cesareb (CC BY-NC 2.0) https://www.flickr.com/photos/cesareb/8620647452

Our story last week about the impacts of predators on Chinook salmon populations in Puget Sound continues to gather strong interest from our readers. Several thousand viewed it after it came out last Thursday, and it was reprinted in the Kitsap Sun on Monday.
The story was written by PSI senior writer Christopher Dunagan and reports on a new study showing that area seals and sea lions are eating a much higher amount of threatened Chinook than previously known. Many questions still remain, but it is the first time that a peer-reviewed study has attempted to quantify these predator impacts to such a degree and in such detail.
Here are a few highlights: As many as one in five young Chinook are eaten before they can make it out of Puget Sound into the open ocean. Area seals and sea lions eat twice the amount of Chinook as do Puget Sound’s endangered orcas, and six times the annual commercial and recreational catches from local fishermen combined. Scientists attribute the large numbers to an increase in seals and sea lions since the 1970s after the animals were protected under the Marine Mammal Protection Act.
Not surprisingly, scientists and policymakers will have to look more closely at these numbers to determine what to do. Seals and sea lions are rightly protected, and old (and undesirable) policies of hunting the animals to protect salmon are not an option. Scientists say that even if such policies were possible, there is no saying that they would actually protect the salmon population.
The fact is that the seals and sea lions are just doing what they do naturally, and while their populations are healthy, there aren’t necessarily more of them than there should be. Some would argue that this study is a reminder that we need to continue to recover habitat and create better conditions for the salmon to withstand what are essentially normal pressures from the environment. Historically, Puget Sound’s Chinook and predators co-existed just fine, but that was before millions of humans started destroying the local streams and floodplains, degrading beaches and polluting the water. See a harbor seal with a salmon in its mouth? That can also be seen as a sign of Puget Sound’s health.

Study says predators may play major role in Chinook salmon declines

Sea lion sunbathing between meals in Seattle's Eliott Bay. Photo: Johnny Mumbles (CC BY 2.0) https://www.flickr.com/photos/mumbles/3283168713
Sea lion sunbathing between meals in Seattle’s Eliott Bay. Photo: Johnny Mumbles (CC BY 2.0) https://www.flickr.com/photos/mumbles/3283168713

A new study shows that increased populations of seals and sea lions are eating far more of Puget Sound’s threatened Chinook than previously known, potentially hampering recovery efforts for both salmon and endangered killer whales.
Read the story in Salish Sea Currents.