Starting in fall 2024, Washington will use drones to monitor the local seal and sea lion populations, the state's Department of Fish and Wildlife announced in late September. The department will send drones along both the coast and certain rivers, with the goal of obtaining a more accurate count of the species of marine mammals.
Currently, the department plans to send drones along the Nisqually, Dosewallips, and Duckabush river estuaries in order to count harbor seals. These flights will occur a few times per month through October 2025 , the department says.
According to WDFW lead mammal researcher Casey Clark , the implications of the research go beyond just finding out how many seals are in Washington.
"Counting these harbor seals will help WDFW estimate the consumption of salmon and steelhead by seals in these locations," Clark stated in a news release.
According to Clark, the seal abundance counts will be used as part of a larger project.
"The goal of our current work...is to study year round harbor seal diet and abundance, as well as a salmon smolt survival study conducted by the partners listed above," Clark said in an email to McClatchy.
He noted that the work is being conducted in partnership with researchers at the National Oceanic and Atmospheric Administration's Northwest Fisheries Science Center , the Port Gamble S'Klallam Tribe , the Nisqually Tribe , and Long Live the Kings, an organization dedicated to preserving the salmon population in the northwest.
Clark went on to say that information will be used "to generate quantitative estimates of the numbers and life stages of salmonids consumed by these seals in the estuaries of the Nisqually River in southern Puget Sound and the Duckabush and Dosewallips rivers in Hood Canal."
Clark said that the researchers plan "to use drones to count seals on haulouts," areas where the mammals rest on the shore, and "near these river mouths each month to inform our abundance estimates." The data, Clark said, will help officials understand how seals are affecting salmon population recovery.
"The results of this work will be used to quantify harbor seal predation on salmon and steelhead in these rivers to allow fish managers to compare the relative impacts of this predation to other sources of mortality and prioritize salmonid conservation efforts," Clark said.
Seal and sea lion population growth in WA
Seals and sea lions have seen their populations grow along the west coast of the U.S. in recent decades, which is thought to contribute to the struggles of the region's salmon, according to the Washington Academy of Sciences.
In fact, according to a 2003 report published in the Journal of Wildlife Management , the Marine Mammal Protection Act of 1972 forced the state to stop its population control program, leading the number of harbor seals observed to increase by somewhere between seven and ten times by the turn of the millennium.
Fast-forward two decades, and the impact in the Pacific Northwest is clear.
According to a 2024 study, the harbor seal population in the southern Puget Sound is roughly ten times what is was in 1980, while the abundance of harbor seals in the Hood Canal has actually leveled off since its peak in the early 1990s. The report also found that group of harbor seals in the northern part of Washington , as well as its southern coast, have seen their population growth slow after a rising quickly through the 1980s and 1990s.
Clark said that these figures represent the populations recovery, not unchecked growth.
"Important context to these counts is that harbor seals were heavily depleted by hunting and state sponsored culls leading into the 1970s when our time series begins, so the big increases in numbers represent a recovery from exploitation by humans rather than an uncontrolled population explosion," Clark said.
Seal and sea lion population control efforts
That growth has implications for the state's salmon population.
A 2016 DFW report estimated that, while Chinook salmon only represent between one and two percent of harbor seals' diets over the spring and summer months, the region's seals eat over 47,000 juvenile Chinook salmon a day during peak months. Clark said this isn't thought to be the cause of the decline in salmon abundance, but it is detrimental to recovery efforts.
"The growth of these pinniped populations coincides with declines in many salmonid species, but is not considered to be the driving factor for the declines," Clark said. "That said, abundant predators can have an outsized impact on struggling prey populations."
According to the Washington State Recreation and Conservation Office, habitat destruction, pollution, overfishing, environmental changes and increased competition for food and resources are the driving factors behind the decline.
Clark said that sea lion populations can be difficult to measure, since the California sea lion tends to breed farther south over the summer, before dispersing. However, its population is estimated to be at the highest level that the ecosystem can sustain, according to DFW.
In the past, Washington and Oregon have explored "non-lethal deterrents," such as deploying underwater firecrackers and shooting gun shells designed to scare the mammals away, in an attempt to curb sea lion population growth and spur salmon population recovery.
After receiving approval from NOAA in 2020, both states implemented a program to euthanize sea lions around the Columbia River.
© 2024 The Bellingham Herald (Bellingham, Wash.). Distributed by Tribune Content Agency, LLC.
