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Sea Lions and Humans vs Salmonoids

by DickEK Community
Daily Kos, December 29, 2022

One thing sea lions do is eat a lot of fish.

Estimated minimum number of adult salmonids consumed by pinnipeds and estimated total number of pinnipeds seen at Bonneville Dam from 2002 to 2011. There are six species of sea lion worldwide, but this post only discusses the two species inhabiting the Pacific Ocean: the Steller Sea Lion (SSL, Eumetopias jubatus ) and the California Sea Lion (CSL, Zalophus californianus). The SSL is the more northerly of the two and its range goes from Japan to Kamchatka, across the Bering Sea through the Aleutians to Alaska, then south to mid-California. The CSL ranges from lower Baja California (including the Gulf of California) to Vancouver Island, British Columbia.

My interest in sea lions began in grad school. I spent several years at Oregon State University and the University of Oregon, where both schools are about an hour drive to the Central Oregon Coast, allowing me to become quite familiar with it. A must-see site, which I have returned to several times in the ensuing decades, is the Sea Lion Caves. Winter is the best time to go.

Although it is wet, windy, and cold, no one else will be there so you have the coast to yourself. That includes easy-to-find parking for views of storm-driven surf crashing against the continent's margin. Also, sea lions leave in Spring for birthing of this year's crop and mating for next year's pups, but you can expect a full house during Winter.

Ranges for the SSL and the CSL overlap, but, if mating/birthing are not involved, they play well together, as can be seen by the peaceful haul-out in Yaquina Bay, Newport, Oregon. As a general rule the SSL is lighter colored and larger than the CSL. There will often be more SSLs in places on Oregon's coast than CSLs, partly because female CSLs, rarely, if ever, go as far north as Oregon.

Sea lions have been hunted by indigenous populations around the Pacific Rim and down the North American West Coast and have done so for the past many, many millennia -- yet there were still sea lions in the waters. Sometime around 1960, the SSL population numbers began to decline for unknown reasons. Loughlin, et. al. (1992) estimated a world-wide decline of about 60% by 1989. Some have estimated as high as an 80% decline from 1970s to the early 2000s. Thus begins my sea lion saga.

Recognizing that declining numbers of sea lions was ecologically unhealthy, Congress enacted The Marine Mammal Protection Act of 1972, which prohibited the taking of protected sea mammals, and defines "take" as follows: "The term "take" means to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal." Sea lions and seals must be left alone to do whatever they do while rebuilding their population numbers. However, the act permitted waiver of the "taking" prohibition if certain conditions prevail.

One thing sea lions do is eat a lot of fish. It wasn't until we noticed that a sea lion's diet included some of our favorite fishes that we became concerned. Whenever man-made construction projects impede the migration of fish, the fish will pool at the choke point while figuring out what comes next. What comes next are the sea lions, and people get upset with sea lions because we didn't foresee the unintended consequences of out project. Sea lions are quite adept at locating food and, once found, reluctant to leave the source alone. This leads to some stories involving sea lions and lunch, as shown by the CSL (named Herschel) in the B&W photo swallowing a steelhead whole.

In 2020 the State governments of Washington, Oregon, and Idaho, together with various indigenous tribes, had requested, and received, permits to kill 616 sea lions over a 5-year period. How did we get from absolute protection to sanctioned killing in 50 years?

Herschel, the very hungry sea lion. The following story was covered during the 1980s and 1990s by the Seattle Times, the Seattle Post-Intelligencer, and the Hakai Magazine. Steelhead (Washington's State Fish) are an iconic sports fishery species in the Pacific Northwest. When steelhead pooled in Elliot Bay (Seattle) awaiting their turn to go up the ladder at the Ballard locks enroute to spawning in Lake Washington, Herschel, the very hungry California Sea Lion and his fellow travelers saw easy pickings.

Since the sea lions were seen eating fish (sea lions prefer to eat their meals at the surface), they were blamed for the subsequent crash in the steelhead run, although the true causes may not have involved sea lions. The MMPA prevented killing sea lions so non-lethal methods of discouragement were tried -- underwater noise makers, electric wires, catch here and release elsewhere. Unfortunately, the sea lions returned to their human-created smorgasbord much faster than anyone would have guessed. This dance lasted for years. Eventually Herschel and company stopped going to the Ballard Locks since there were too few steelhead to bother with, and now that steelhead run is extinct.

An aerial photo of the Willamette Falls, by water volume, is the second largest natural falls in the continental US. A similar story is playing out at Bonneville Dam on the Columbia River and at Willamette Falls on the Willamette River in Oregon. The first CSLs arrived at Bonneville in the late 1980s, while the first SSL was sighted in 2003. Non-lethal discouragement methods were tried, and all failed. Sea lions in the Columbia River and at Willamette Falls also eat sturgeon, another threatened fish forbidden to human anglers.

Willamette Falls is a natural barrier and fish have overcame it by themselves for millennia, but now there is a fish ladder for them to congregate at while awaiting arrival of sea lions.

There hadn't been a lot of research on sea lions prior to passage of the MMPA in 1972, and it wasn't until 1990 and later that some important facts about SSLs became known. The National Marine Fisheries Service (NMFS), NOAA, announced in the Federal Register (1990) that the SSL would be classified as threatened, meaning it had the potential to become endangered. Seven years later when more information had been gathered on the SSL the NMFS announced in the Federal Register (1997) the existence of two Distinct Population Segments (DPS) of the SSL: a Western DPS and an Eastern DPS (see map). The east-west longitudinal division line passed through Cape Suckering, Alaska, at 144o W. longitude. They also listed the Eastern DPS (West Coast of North America) as threatened, while classifying the Western DPS as endangered.

Recovery management plans were established and the SSL numbers began to increase over the following years, allowing the NMFS to write in the 2013 Federal Register that the Eastern DPS had recovered sufficiently to remove them from the threatened or endangered list. The Western DPS would remain on the endangered list, where it resides today.

Bounties and commercial hunting (for use as canned pet food!) once drove California sea lions toward extinction, but they rebounded once the Marine Mammal Protection Act (MMPA) of 1972 became law, and they were never placed on either the threatened or endangered list. Currently their robust numbers indicate no need for further protection and their numbers are about at their habitat's carrying capacity. Nevertheless, it has been noted during the past two-plus decades that CSLs have been dying of cancer at an unusually high rate. The Marine Mammal Center (MMC) in Sausalito, CA, estimates that about 20-25% of all adult CSLs have or are developing cancer.

Scientists at the MMC have linked the cancer to a herpes virus and to a chemical pollutant. In humans the virus appears to be caused by exposure to toxins, such as chemicals or tobacco tars. The scientists go on to note that "High levels of persistent organic pollutants such as DDT and PCBs have been found in the blubber of California sea lions." Finding DDT was a puzzle because use of the mosquito-killer had been discontinued for decades. It wasn't until recently that marine scientists discovered as many as 25,000 barrels loaded with DDT near Catalina Island. Letters were sent to Congress, but the barrels are still on the seabed.

Sea Lions continued to eat steelhead and salmon congregating at man-made barriers. In response to a joint request from the States of Washington, Oregon, and Idaho, the NMFS-NOAA convened a mandated task force to consider the request for (later approved in Mar, 2008) the killing of up to 85 CSLs annually in the Columbia River. At that time SSLs were listed as threatened under the Endangered Species Act of 1973 and could not be killed. Those CSLs killed must be individually identifiable from others, must have been observed eating salmonoids during a run (Jan 1 to May 31), and were sighted after non-lethal removal methods failed for each particular sea lion. A little-known fact stemming from the individually identifiable requirement was that some sea lions were captured and branded with a hot iron.

The approval letter states that "all but one member of the task force concluded that California sea lions are having a significant negative impact on the recovery of Columbia Basin threatened and endangered salmonids". On this basis the Secretary approved the request. The one dissenting voter argued that there were at least three far more negatively impacting factors, making the minimal sea lion predation seem trivial compared to the ones being ignored. The single most damaging factor is the dams themselves, which killed far more fish than any other factor. The second most damaging factor is harvest, due to commercial over-fishing and sports fishing. Sea lions are a distant fourth.

The Humane Society of the United States filed an appeal, and the 9th Circuit Court of Appeals (2010) ruled in favor of the Humane Society. As described by the Vancouver, Washington newspaper, The Columbian, "Sea lions may be eating imperiled wild salmon at the dam, but federal authorities now must explain how it's OK to kill a natural predator while allowing human fishermen to inadvertently kill an equal or greater proportion of wild fish". The States were unable to reconcile this contradiction to the Court's satisfaction and elected not to pursue this current request through the courts any further, preferring instead to "fix the flaws" in the current request.

Capturing in the Columbia and releasing elsewhere went on for a long time with little or no apparent benefit to the salmon or steelhead runs. In 2017 The Oregon Department of Fish and Wildlife applied for a permit to kill CLSs only and received authorization in 2018. Finally, Congress amended the MMPA in 2018 to explicitly permit killing of SSLs. The States of Washington, Oregon, and Idaho, together with various Native American tribes, received authorization in 2020 to kill 540 SSLs and 176 CSLs over a 5-year period, which is still in effect. Will it work? Stay tuned.

As a parting "I-told-you-so", I'd like to mention a story posted on the Canadian EcoWatch website dated April 17, 2022. The headline is a grabber: "Sea Lions Break into B.C. Salmon Farm and Feast for Weeks". Perhaps the fish pen designers thought only of keeping the fish inside and did not give enough thought to keeping predators outside. This particular salmon farm is located near Tofino, British Columbia, on the Pacific Ocean-facing western shore of Vancouver Island.

There is too much to be said about salmon farming in the Pacific Northwest to say it now so that will have to wait for another story.

Related Pages:
Sea Lions, Seals Might be Hampering WA Salmon Recovery. What Can Be Done? by Isabella Breda, Seattle Times, 1/15/23
NMFS Authorizes Sea Lion Removals to Save Columbia River Salmon by Lynda Mapes, National Fisherman, 8/27/20

DickEK Community
Sea Lions and Humans vs Salmonoids
Daily Kos, December 29, 2022

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