School of Aquatic and Fishery Sciences

The Columbia River is home to one of the West Coast’s most important Chinook salmon runs. Through late spring and early summer, mature fish return from the sea and begin their arduous journey upriver to spawn. In recent years, these fish have faced an additional challenge: hungry California sea lions.

A new University of Washington and NOAA Fisheries study found that sea lions have the largest negative effect on early-arriving endangered Chinook salmon in the lower Columbia River. The results were published Oct. 19 in the Journal of Applied Ecology.

Opportunistic sea lions have learned that by swimming as far as 145 miles upriver, they can easily feast on migrating salmon, including those hindered by the Bonneville Dam.

“We investigated whether mortality rates varied depending on the specific threatened Chinook salmon population, determined by when they arrive in the river,” said lead author Mark Sorel, a doctoral student at the UW School of Aquatic and Fishery Sciences. “We found that, based on their individual return timing and the abundance of sea lions in the river when they return, individual populations experience different levels of sea lion-associated mortality.”

Researchers learned that the earliest arriving populations of Chinook salmon experienced an additional 20% mortality over previous years, and the later arriving populations experienced an additional 10%. This increase in mortality was associated with increased sea lion abundance at those times of year in the period of 2013 to 2015 compared to the period of 2010 to 2012.

The numbers of California sea lions are highest at the mouth of the Columbia in early spring, before they depart for their breeding grounds in southern California. The researchers also discovered that the earliest arriving salmon migrate through the lower Columbia River more slowly than those arriving later in the season, thereby increasing their exposure to predation.

“This information on how different populations are affected by sea-lion associated mortality is key because recovery of endangered Chinook salmon requires multiple of the individual populations to be healthy,” said Sorel.

California sea lions have seen their numbers rebound along much of the U.S. West Coast since the passage of the Marine Mammal Protection Act of 1972, which protects them from being killed, captured and harassed. The increased presence of sea lions is now at odds with the endangered salmon populations on which they feed, putting managers in a difficult position.

Researchers are concerned that something must be done quickly as these hunting behaviors are learned, and the problem could continue to grow exponentially. In August, the National Marine Fisheries Service granted approval for Washington, Idaho, Oregon and several Pacific Northwest tribes to capture and euthanize both problematic California and Steller sea lions within a larger area of the lower Columbia and Willamette Rivers. Previously, only California sea lions could be killed in these rivers if managers deemed them a threat to salmon.

This complicated decision was enacted after non-lethal methods, such relocation and hazing, to limit the impact sea lions have on salmon — plus some targeted lethal removal — were met with limited success.

“This is often a challenging management problem as both sea lions and salmon are of strong interest to the public, and both are protected under federal statutes,” said Sorel. “Management must consider multiple social values and operate within existing legal frameworks.”

Continued monitoring will help to reduce the remaining uncertainty about the effects of sea lions on salmon and the expected outcomes of alternative management actions.

Other co-authors are Richard Zabel and A. Michelle Wargo Rub of NOAA Fisheries Northwest Fisheries Science Center; Devin Johnson of NOAA Fisheries Alaska Fisheries Science Center; and Sarah Converse, leader of the U.S. Geological Survey Washington Cooperative Fish and Wildlife Research Unit and UW associate professor. This research was funded by the National Marine Fisheries Service West Coast Protected Resource Division.

For more information, contact Sorel at marks6@uw.edu and Converse at sconver@uw.edu.

A small subpopulation of polar bears lives on what used to be thick, multiyear sea ice far above the Arctic Circle. The roughly 300 to 350 bears in Kane Basin, a frigid channel between Canada’s Ellesmere Island and Greenland, make up about 1-2% of the world’s polar bears.

New research shows that Kane Basin polar bears are doing better, on average, in recent years than they were in the 1990s. The study, published Sept. 23 in Global Change Biology, finds the bears are healthier as conditions are warming because thinning and shrinking multiyear sea ice is allowing more sunlight to reach the ocean surface, which makes the system more ecologically productive.

“We find that a small number of the world’s polar bears that live in multiyear ice regions are temporarily benefiting from climate change,” said lead author Kristin Laidre, a polar scientist at the University of Washington Applied Physics Laboratory’s Polar Science Center.

If greenhouse gases continue to build up in the atmosphere and the climate keeps warming, within decades these polar bears will likely face the same fate as their southern neighbors already suffering from declining sea ice.

“The duration of these benefits is unknown. Under unmitigated climate change, we expect the Kane Basin bears to run into the same situation as polar bears in the south — it’s just going to happen later,” Laidre said. “They’ll be one of the last subpopulations that will be negatively affected by climate change.”

All of the world’s 19 polar bear subpopulations, including Kane Basin, are experiencing a shorter on-ice hunting season, according to a 2016 study led by Laidre. This makes it hard for the animals, that can weigh more than 1,200 pounds as adults, to meet their nutritional needs. Polar bears venture out on sea ice to catch seals. In summer when the sea ice melts, the polar bears fast on land.

Laidre led a recent study showing that in the Baffin Bay polar bear subpopulation, which includes about 2,800 bears living just south of Kane Basin, adult females are thinner and are having fewer cubs as the summer open-water season —  when they must fast on land —  grows longer.

“Kane Basin is losing its multiyear ice, too, but that doesn’t have the same effect on the polar bears’ ability to hunt,” Laidre said. “Multiyear ice becomes annual ice, whereas annual ice becomes open water, which is not good for polar bears.”

The new paper looked at Kane Basin bears using satellite tracking data and direct physical measurements to compare from 1993 to 1997 with a more recent period, from 2012 to 2016. The body condition, or fatness, improved for all ages of males and females. The average number of cubs per litter, another measure of the animals’ overall health, was unchanged.

Satellite tags showed the Kane Basin polar bears traveled across larger areas in recent years, covering twice as much distance and ranging farther from their home territory.

“They now have to move over larger areas,” Laidre said. “The region is transitioning into this annual sea ice that is more productive but also more dynamic and broken up.”

Observations show a profound shift in the sea ice in Kane Basin between the two study periods. In the 1990s, about half the area was covered in multiyear ice in the peak of summer, while in the 2010s the region was almost completely annual ice, which melts to open water in summer.

Even though there’s now more open water, the marine ecosystem has become more productive. Annual sea ice allows more sunlight through, so more algae grow, which supports more fish and in turn attracts seals.

“Two decades ago, scientists hypothesized that climate change could temporarily benefit polar bears in multiyear ice regions over the short term, and our observations support that,” Laidre said.

The subpopulation on the other side of Ellesmere Island, in Canada’s Norwegian Bay, could be in a similar situation, she said, though no data exist for those animals.

If conditions continue to warm these northernmost polar bears will likely face the same fate as their southern neighbors. Kane Basin polar bears have only much deeper water to turn to farther north.

“It’s important not to jump to conclusions and suggest that the High Arctic, which historically was covered by multiyear sea ice, is going to turn into a haven for polar bears,” said Laidre, who is also an associate professor in the UW School of Aquatic and Fishery Sciences. “The Arctic Ocean around the North Pole is basically an abyss, with very deep waters that will never be as productive as the shallower waters to the south where most polar bears live.

“So we are talking about temporary benefits in a limited area and to a very small number of bears.”

Co-authors are Eric Regehr, Harry Stern, Benjamin Cohen and Patrick Heagerty at the UW; Stephen Atkinson and Markus Dyck with the Government of Nunavut in Canada; Erik Born with the Greenland Institute of Natural Resources; Øystein Wiig at the University of Oslo in Norway; and Nicholas Lunn, with Environment and Climate Change Canada.

Major funders include the governments of Canada, Denmark, Nunavut and Greenland; NASA; and the World Wildlife Fund.

For more information, contact Laidre at klaidre@uw.edu.

NASA grant: NNX13AN28G NNX11A063G

This article was originally published in UW News

A cooler full of fish might not be the only thing anglers bring back from a trip to the lake. Unknowingly, they may also be transporting small aquatic “hitchhikers” that attach themselves to boats, motors ― and even fishing gear ―  when moving between bodies of water.

Considerable research shows that aquatic invasive species can completely transform ecosystems by introducing disease, out-competing and eating native species, altering food webs, changing physical habitat, devastating water-delivery systems and damaging economies. Furthermore, once established, eradication of nuisance species is near impossible, and management can be extremely difficult and costly.

Although preventative measures have been enacted to reduce their introduction and spread, such as mandatory watercraft inspections, educational programs and even dogs trained in sniffing out invasive species, these aquatic stowaways still manage to find their way into new water bodies around the country.

One of the many challenges is identifying how these species spread through human movement. A new University of Washington study uses passive data from a fishing technology company to model the movement of anglers and predict where aquatic invasives may be spreading. The findings were published Sept. 2 in the journal NeoBiota.

“Focusing on anglers allows us to look at a population that uses a wide range of gear on the water; therefore, they have the potential to move a very wide range of species,” said Rachel Fricke, a graduate student at the UW School of Aquatic and Fishery Sciences. Fricke’s research on invasive species is a continuation of her undergraduate capstone project which she also completed at the school.

The researchers used data provided by ReelSonar, the Seattle-based developer of the pocket-sized fish finder iBobber. The iBobber syncs with an angler’s smart device and collects multiple pertinent data points, including fishing location. To date, over five million locations have been recorded from around the world.

“In the past, ecologists have done an incredible job extracting big datasets from the web without necessarily working with the organizations who collected the data in the first place,” said co-author Julian Olden, a professor of aquatic and fishery science. “This is to be expected, but I believe that real creativity in the future will come from more authentic collaborations where both ideas and products are co-generated.”

Previous studies relied on optional online forms, requiring anglers to log fishing trips from each location they visited. With ReelSonar’s passive data, these points are generated automatically, offering researchers an exciting opportunity to further understand where people are moving and when.

The authors specifically looked at location data in the United States and narrowed it down to identify individual trips made by anglers. By quantifying geographic patterns of fishing activities and assessing how these patterns change seasonally, the authors explored angler behavior (fishing frequency and distance traveled) between sites.

“We were predominantly interested in where people were fishing and the amount of time between their trips to different lakes,” said Fricke. “The length of time determines the types of species anglers unintentionally move, as each species has very different survival rates out of the water.”

The authors were also interested in the routes people were using to travel between fishing locations.

What they found was the vast majority of road distances traveled are over small spatial scales. Most anglers are staying near urban areas, but fishing multiple different lakes or rivers in a small radius over a short amount of time. The authors then focused on “invasion hubs,” water bodies that have many linkages via human movement to other nearby water bodies. The timeframe of these movements, which was mostly two days or fewer, fell well within the out-of-water survival threshold for the six invasive species identified in the study.

“Boiled down, people are moving a lot and they’re moving quickly from one place to the next, which has the potential to move a number of different invasive species,” said Fricke. “I don’t think we need to change the preventative measures that we use in light of this data, but it does enable us to better locate those preventative measures in space and time.”

Identifying highly trafficked roads near invasion hubs can be valuable from a management perspective and can help influence where roadside inspection stations and educational signage are placed.

“If we see points in these data where invasion hubs exist and where resources are not being allocated, this gives managers the opportunity to identify and implement required boat cleaning and boat inspection stations in those locations,” said Fricke. “This kind of data offers a ripe opportunity to reassess where we’re enacting preventative measures and to be more strategic about where we do that.”

Other co-authors are Spencer Wood and Dustin Martin of ReelSonar. This research was funded by the Gordon and Betty Moore Foundation, the Alfred P. Sloan Foundation, and the Edward Allen Power, W.F. Thompson and Mary Gates Endowment scholarships.