Puget Sound Orcas losing most pregnancies due to Salmon Decline


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Orcas are losing their babies at an unprecedented rate. The solution may lie 400 miles away.

By: HANNA BROOKS OLSEN For: Pacific Magazine, September 21, 2017

Follow the link to full article: https://psmag.com/environment/why-do-most-orca-pregnancies-end-in-miscarriage

Writing in 1916, conservationist John Muir noted that "there is not a 'fragment' in all nature, for every relative fragment of one thing is a full harmonious unit in itself." A century later, in the Pacific Northwest, land managers, tribal leaders, environmental stewards, lawmakers, and business interests are locked in a fight over which harmonious units and relative fragments can be rearranged to satisfy all parties.

But while they grapple over the details of regulations and policy changes, and the various perceived and demonstrated economic effects any such legislation may have, whales continue to miscarry at an unprecedented rate.

In the salty waters off the coast of Seattle, the region's orca population is spontaneously miscarrying the majority of its pregnancies, according to a recent study by researchers at the University of Washington, published inPLoS One. By studying the feces of orcas through the use of detection dogs, the researchers tracked the whales' hormones over time. Their findings were stark: Sixty-nine percent of all detectable orca pregnancies ended with miscarriage; 33 percent of those pregnancies failed in the late stages of gestation or immediate postpartum.

While the temperature of the ocean, boating, and commercial shipping are often looked to as identifiable reasons for orca stress, one of the most important places to look for answers may actually be on land, where the human footprint has choked off the primary food source of the Southern Resident killer whale population—the Chinook salmon.

The Center for Whale Research, which has been surveying Puget Sound killer whales for decades, reports that Chinook make up about 80 percent of the average orca's diet; each whale must consume between 18 and 25 salmon per day just to retain its energy levels. To feed the entire population of Southern Resident killer whales, the Puget Sound and surrounding waterways must provide at least 1,500 salmon per day.

But since the Pacific Salmon Commission began tracking salmon in 1984, it has noted a 60 percent reduction in the population of Chinook. The commission estimated under half a million were left in the Salish Sea in 2010—less than a year's supply of fish for the orca.

While researchers have known for years that the reduction in supply has a direct effect on the area's killer whale population, the University of Washington study sheds light on a new, previously under-diagnosed problem: It appears that lower numbers of salmon put undue burden on pregnant whales, who need even more of the high-fat, high-protein fish to feed both themselves and their growing babies.

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WFF Supporter
Since first hearing and then reading about the association of southern resident killer whales and their affinity for Chinook salmon as preferred forage, I've had certain misgivings. First, although I understand the concept of search image and other preferences related to foraging, this Chinook preference appears to defy the principle of optimal foraging theory. Chinook are only optimal when they are both individually large and occur in abundance. Chinook salmon in the Salish Sea haven't satisfied that criterion for at least the last half century.

In order for large Chinook to occur in abundance, it would require healthy populations of Fraser and Puget Sound spring, summer, and fall Chinook. A significant decline has occurred in the last 20 - 25 years or so, but it's a modest drop compared to the reduction since the mid-1960s.

In any time period, Chinook abundance is characterized by their year round presence in the Salish Sea and Puget Sound. However, Chinook are seasonally drowned to nearly insignificant abundance compared to the seasonal abundance of Fraser sockeye in the summer, pink salmon in late summer, and chum salmon in the fall. Chinook is my favorite salmon table fare, but if faced with a survival issue, I'm pretty sure I could lower my standards, at least on a seasonal basis, to dine on the most abundant salmon species.

Lastly, there is the issue of adaptability, as in adapt or perish. At the same time as the recent decline in Puget Sound salmon abundance, marine mammals have grown their populations exponentially. Yet it supposedly is only the transient orca population that forages on marine mammals. Perhaps nature is telling the southern residents that their lack of adaptability to changes in forage abundance is a signal that they should go extinct for being such fastidious and picky eaters. Eat the forage that is abundant or disappear.

The orca biologists tell me that there is nothing illogical about the prey preference of the southern residents. Wildlife biology is full of accounts of predator - prey relationships. Predators that are keyed to a single prey species typically experience cyclical ups and downs in response to changes in the prey populations. However, most predators demonstrate a certain amount of opportunism and switch to other prey species when the preferred prey is less abundant. Wolves evolved to prey on caribou, elk, and deer. However they will kill cattle and sheep when and where those alternative prey species are more abundant and more efficient to capture than the preferred species. Same with cougars; they are keyed to prey on deer, but in the suburbs where dogs and cats are abundant, and deer are harder to hunt, well cougars and wolves appear to be more adaptable than those persnickety southern resident orcas.

Consequently I'm having a hard time sympathizing with the southern resident killer whales, high miscarriage notwithstanding.


Director of Stoke
I heard a biologist say that the orcas would not eat the Atlantic salmon that escaped the pens. I was thinking large, stupid fish, easy prey, etc. Apparently the orcas are a bit set in their ways...


Active Member
I'm not at all concerned about Orca's who visit the PNW to devour salmon. Nor am I concerned about resident Orca. From a conservation viewpoint, we pay too much money for the salmon and get zero return on every salmon killer whales consume. It would be a good thing if the killer whales in PNW waters would begin to feed on killer whales and nothing else.


Active Member
Good points Salmo. And, I don't have the specialty background. I just learned that there are 3 orca groups on the west coast.

I heard that Orcas can live for 50 years (males), and 100 (females). Females rule the pod by age. Perhaps their adjustment abilities are slower than humans. Obviously, sympathy has nothing to do with an orca pod being human intelligent and going after the watchers that hover in rubber rafts.

The more important take away is that these animals, the fish stocks, are indicators of biome going bad; and we are saying the animals are stupid?

I chopped the article at about 50 percent. There were additional points and sub topics.


Active Member
Killer whales aren't in any trouble, they inhabit almost all coldish oceans on the planet. The only good thing I can think about regarding Orca is they like seals and sea-lions, personal pet peave. If we can't convince them they should feed on sea lions instead of salmon then we should teach them that eating salmon is bad for their life expectancy. They are smart enough to learn if we tried to educate them.
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Cetacean brains, such as those of dolphins (left) and humpback whales (right), have even more cortical convolutions and surface area than human brains do. Does that mean they're smarter?

Since they have not polluted the oceans, I am thinking they are smarter.


Active Member
Nice fractal designs. I don't think we can judge animals in terms of human concepts, GT. To do so reminds me of Lassie, Flipper and RinTinTin. Fantasy.

Having a wake for a dolphin, which can be an interpretation of the article, clearly is not the message. Humans are the cause of this disruption, and decline of salmon, we know that, yet play games. One side wants the last trophy before we poison ourselves. The other sees correcting causes of environment destruction eventually turning the tide and resolving the present losing battle.

Those people holding a less religious rictus but play the worldview fake are scamming for profit. It's no different than profiteering from hurricane tragedy. One guy is demonized for gouging bottled water prices. Another is praised for tripling airline fares. Do stock profits define morality?

It's much easier to say there is nothing wrong with us. Keep it status quo. What's the fake buzzy? "Natural change?"

Jim Travers

Active Member
I'm not at all concerned about Orca's who visit the PNW to devour salmon. Nor am I concerned about resident Orca. From a conservation viewpoint, we pay too much money for the salmon and get zero return on every salmon killer whales consume. It would be a good thing if the killer whales in PNW waters would begin to feed on killer whales and nothing else.

I pulled one them whales up on a big ass dry one time. Scared me!!!! Didn't wanna git close, so I yanked that rod back and ripped that thing right outit's mouth!!! Almost fell in the water m'self!!!!!

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