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Sea bound visitors

Fisheries biologist sheds light on why killer whales arrived in Gastineau Channel

Posted: Friday, March 04, 2011

A pod of orcas arrived last week in Gastineau Channel. The pod turned heads and stopped traffic around the lunch hour on Friday as they moved beneath the Douglas Bridge, swimming slowly along the shoreline and in and out of breakwaters during a low winter tide.

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Libby Sterling / Juneau Empire
Libby Sterling / Juneau Empire

Orca visits to Juneau’s urban areas are rare, though not exceptional. However, their reasons for visiting are often known only to whales themselves.

John Moran, a research fisheries biologist for the National Marine Fisheries Service at Auke Bay Laboratories, said he believes the pod entered the channel looking for harbor seals or sea lions. He thinks this gang was a transient one, based on their behavior and group size. Roughly six to eight whales made up the pod.

“Transients are usually in smaller groups,” he said. “(This pod) was within the range of being a transient pod.”

Resident groups typically consist of 10 or more mammals, with groups of 20 not uncommon.

Another way to distinguish residents from transients is by examining their behavior, the general shape of their dorsal fins and the coloration of their saddle patches, he said.

“Generally, transients have a more triangular dorsal fin. They move silently, compared to residents, who are often chatting away,” Moran said.

The saddle patch is the white or greyish area at the base of the dorsal fin. According to the book “Transients: Mammal-Hunting Killer Whales” by John Ford and Graeme Ellis, residents have saddle patches that may be either uniform in coloration or contain various amounts of black — the latter known as “open saddles.” In transients, the saddle patch is typically quite large compared to residents, and open saddles are not found.

While sightings of killer whales in Gastineau Channel happen only a few times a year, Moran said this year they’ve been notably active in Favorite Channel and Stephens Passage.

“They’ve been around a lot lately,” he said. “It seems we have a lot of killer whales this time of year. Maybe the (seal or sea lion) pups are getting bigger, and starting to wander a bit more. I was out on the water in the middle of January. There were residents and transients all over.”

Moran said he has noticed a common local route the transient pods will follow.

“They start out by Benjamin Island, where the sea lions are. And they’re there because there’s a large group of herring biomass out there. The sea lions eat those, then the killer whales eat the sea lions,” Moran said. “I see them come by Lena Point, then maybe go into Auke Bay. Harbor seals (another of their favorite foods) can be found near Deharts. Then I suspect they go around Douglas Island. There are usually seals by Dipac.”

The draw of Dipac could be one reason the group headed up the channel. Transients will sneak along the shoreline, and follow the contours in and out of small bays and narrow passages while in search of prey. The fact they timed their arrival with a low tide was just happenstance, Moran said.

Yet, speculation about this most recent visitation continues. Rumors of feeder kings in the area have been circulating around town.

That, Moran said, complicates things.

“Usually the resident groups are bigger. But, maybe a small group broke away,” he said.

Despite this possibility, Moran still believes the pod was a group of transients. He spotted two more transients passing Lena Point at 8 a.m. Thursday morning.

According to Ford and Ellis, transient killer whales can be found year-round in coastal waters, whereas residents show strong seasonality. They are most common in inshore waters from June through October, corresponding to the timing of salmon migration.

Regardless of what drew this particular pod into Juneau last week, one thing is for sure.

“It’s kinda neat that these big animals can be seen right out our front door,” Moran said.

• Contact Outdoors editor Abby Lowell at abby.lowell@juneauempire.com.



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