Puget Sound orcas: What they eat, and why it matters

| West Seattle news | Wildlife

Story and photos by Jonathan Stumpf
Reporting for West Seattle Blog

“It is a week for the Puget Sound orcas,” said The Whale Trail‘s founder, Donna Sandstrom, to a crowd of roughly 40 at last night’s orca-research presentation her organization sponsored at the Duwamish Longhouse.

She was referring not only to the first-ever OrcaFest that The Whale Trail and Killer Whale Tales presented on Alki last Sunday (WSB coverage here), but also to the Beach Drive announcement hours earlier about the Maury Island deal that would preserve King County’s longest remaining stretch of undeveloped Puget Sound shoreline (WSB coverage here).

But the main event for this presentation: Brad Hanson of NOAA Fisheries, taking the audience through the known diet of the Southern Resident orcas in a colorful discussion titled “In Search of Spew, Poo and Goo: Learning about Orcas from What They Leave in Their Wake,” essentially a preliminary look into his years of innovative research.

As Hanson explained to the audience, it has only been less than half a century that humans have been studying these whales. The current population of Southern Resident orcas is around 85 and was listed under the Endangered Species Act in 2005 as “endangered.”

Through a variety of studies including the use of a time-depth wildlife computer attached to the whales and the ‘crittercam’ as demonstrated to the audience in a video ‘shot’ by whale K25 — think, whale headcam — Hanson and his team got some informative charts of the whales’ depth and speed, and some very fascinating video footage, but nothing conclusive about the types of salmon they were targeting.

At one point, Hanson was approached by a colleague who had found some whale poo and passed it off to Hanson. He had no idea about the trove of information that was to be found. “Whale poo is a literal gold mine,” said Hanson. “If I had my choice, it[the study] would be on whale poo.”

So began the collection of feces, regurgitations, mucus and food scraps from the Southern Resident Killer Whales (SRKW) and very quickly they were able to identify that although the whales had a fairly diverse diet, it was heavily dominated by chinook, followed by chum salmon (the transient population eats mammals and are not part of this study).

The reasoning? Best science indicates that the large size and high fat content are key. Scientists once thought availability played a key role in their diets, but this was quickly dispelled when the numbers of pink and sockeye — the largest runs of salmon in the Georgia Basin — found in whales’ diets was minimal.

So how many chinook sustains this population? Hanson estimates that the SRKW needs about 30,000 salmon a month to survive. But not to worry, fishermen, these whales aren’t on a local-only, 100-mile diet–the salmon in the study came from 166 different populations in 41 different regions from the Gulf of Alaska to the Central Valley of California.

For more information on the Southern Resident orcas, visit thewhaletrail.org, orcanetwork.org or killerwhaletales.org.

Trileigh November 11, 2010 (9:28 am)

How would one recognize whale poop? If I found some, I’d be happy to turn it over to Hanson, but I don’t know what it looks like.

herongrrrl November 11, 2010 (10:01 am)

:) You’d probably only see it if you were in a boat following a pod of orcas. It looks like blobs of orange goo floating on the water. Kind of the color you’d expect, being mostly salmon.

Joel November 11, 2010 (10:11 am)

The largest factor in the slow recovery of SRKW is the availability of food. The region wide abundance of chinook has steadily dropped since the post WWII building boom. The most dramatic drop in chinook production has occurred in the Columbia Basin, due to the construction of the hydro electric dams. Current estimates for pre-dam fish runs range from 20 to 35 million salmon, although not exclusively chinook. Current total runs of chinook are less than half a million.

Chinook runs into the Columbia start in March with Spring Chinook and extend through the fall with Fall Chinook. For orcas this meant there was lots of prey off the coast. The SRKW leaves Puget Sound after dogs are done and go off to eat out of sight somewhere in the ocean. This is when the Columbia origin chinook are available to the SRKW and together with the paucity of Puget Sound chinook inhibit rebuilding of SRKW populations.

Oddly enough, NMFS does not recognize this in the Columbia River Power System Biological Opinion, mostly because it is an awkward fact that the dam operators don’t want publicized. The Biological Opinion for the Central Valley power and irrigation operations impacts on Central Valley (California) Chinook DOES say that the lack of availability of chinook jeopardizes SRKW. There is no logic to this determination of non-jeopardy by NMFS towards the Columbia Power System. Look to Judge Redden to decide that this BIOP is arbitrary and capricious and to order the federal government to enter into settlement talks with plaintiffs. There will be no remand because the federal government has failed four times to come up with a plan that legally satisfies the Endangered Species Act for salmon or SRKW.

The one thing government can provide for SRKW is food. The only way to get the government to act is to use the courts to force an order upon the feds to take meaningful actions to recover chinook stocks. Our political leaders must realize they can not passively sit aside while NMFS lets SRKW and salmon resources dwindle and that the public expects and demands elected officials push to recover these iconic Northwest species.

Chris November 13, 2010 (12:38 pm)

It does not work to have judges managing the river systems. The Colville Tribe put it best: “It is time to end this litigation and give the BiOp and the Columbia River Fish Accords a chance to work.”

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