Posted by: The ocean update | October 8, 2015

Barrow whalers haul in bonus bowhead killed by unknown causes (Alaska, USA)

A dead young bowhead whale was found offshore near Point Barrow last Sunday. The nature of its death is still being investigated.North Slope Borough Department of Wildlife Management

A dead young bowhead whale was found offshore near Point Barrow last Sunday. The nature of its death is still being investigated.North Slope Borough Department of Wildlife Management

October 8th, 2015 (Alex DeMarban). Subsistence whalers in the nation’s northernmost town have completed a successful season that includes 15 bowheads landed, plus a bonus bowhead hauled ashore after it had been found dead and floating belly up, a 7-foot gash in its underside.

Scientists and whalers who examined the whale, a calf just over 25 feet long, say it was not killed by hunters. Two possible culprits are an attack by killer whales — something that might be on the rise in Arctic waters as sea ice retreats — or a ship strike.

Whatever the cause, many Barrow residents were happy for the surplus muktuk, or blubber, that was distributed in the town of about 4,400 just like meat from the other whales that counted against Barrow’s fall quota.

“It was a gift of God for the community,” said Eugene Brower, president of the Barrow Whaling Captains Association.

The Hopson I whaling crew found the whale on Sunday about 20 miles east of Point Barrow, in the Beaufort Sea, then hauled it ashore to salvage what they could.

Observers initially thought it had been struck by whalers and sunk, only to float to the surface later, buoyed by its internal gas. Such ‘stinker whales,’ as they’re called for their stench, are recovered and shared when their blubber is safe to eat.

North Slope Borough biologists and a wildlife veterinarian who examined the whale weren’t ready to pinpoint a cause of death.

In addition to the ripped belly, the whale had suffered significant bruising to the neck and chest, “blunt trauma” consistent with ramming by killer whales or damage from a ship, said a statement from the borough’s wildlife department.

Orca bite marks were also found on the flukes and flippers, indicating that killer whales attacked the bowhead even if they didn’t kill it.

There was no evidence that the whale had been injured by hunters.

The event, plus a separate bowhead death, has some wondering if orca attacks are on the rise.

On Sunday, federal scientists conducting aerial surveys photographed a different young bowhead floating adrift about 60 miles east of Point Barrow. It had also been attacked by killer whales, with its jaw mangled and a flipper bearing scars from a killer whale attack, experts said.

It’s rare to come across bowheads killed by orcas.

“That’s the first time I heard of killer whale predation on a bowhead,” said Barrow whaling captain Herman Ahsoak, whose crew landed the season’s largest whale at 47 feet, 7 inches long.

But about two years ago, a dead stranded whale was found on shore about 30 miles south of Barrow bearing clear evidence of a killer whale attack, with the lips and tongue ripped out, North Slope Borough biologist Craig George said. It was a first for scientists with the wildlife department, and locals agreed it was unusual for the area.

Orcas have large dorsal fins and don’t do well in pack ice, but they appear to be expanding their range in the Arctic Ocean as sea ice retreats, said Doug DeMaster, a top expert on marine mammals and director of National Oceanic and Atmospheric Administration’s Alaska Fisheries Science Center.

“Less sea ice, more habitat in which to hunt,” bringing them closer to bowheads once protected by ice, DeMaster said.

A new study of bowhead whales harvested between 1990 and 2012 found that scarring associated with killer whale attacks was statistically more frequent in the second half of the study.

The analysis, by George and others, found that the increase could be related to reporting and sampling factors, or more open water and killer whales at high latitudes.

Craig Matkin, a biologist who contracts with NOAA and other agencies on cetacean studies, said killer whales leave “rake mark” scars on the flippers and tail of large whales such as bowheads because orcas restrain the giant prey while others pile on top to drown it.

Matkin, who has long studied interactions between orcas and other whales, said ramming often occurs as killer whales try to drive calves away from mothers.

“The whole point is to scare them and get them to panic so they can drown them,” he said.

Matkin said orcas usually eat the lips and tongue of dead whales first, a flesh-like “tenderloin” that may serve as an entire first course, with some orcas returning later to feed on other parts of the carcass.

The recovered calf’s tongue was not eaten, which is unusual for a killer whale attack, the release from the wildlife department said.

“That’s mysterious,” said George.

He said the weight of the evidence causes him to think orcas killed the calf, but he said it’s difficult to be certain.

“There are lots of questions still,” he said.

To determine what killed the bowhead, the wildlife department is seeking input from “outside experts” in killer whale attacks and ship strikes, including with NOAA and the Woods Hole Oceanographic Institution in Massachusetts.

Arnold Brower Jr., executive director of the Alaska Eskimo Whaling Commission, said the punctures on the flipper and fins looked like they were made by orcas working in tandem like wolves to target nutritious organs through the belly, with some securing the bowhead while others fed.

“It looked they had really pinched in there to hold the flippers and the tail,” he said.

As for the muktuk, it tasted good, with a slight fermented edge.

“It’s got a flavor to it,” he said.

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