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.
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