Whale strandings off Washington-Oregon coast highest in nearly two decades

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Struck by a ship, entangled in crab pots, stillborn, emaciated: It's been a tough three months for whales.

Since April 3, —mostly grays, and humpbacks—have been entangled and/or stranded on the beach in Oregon and Washington in numbers not seen in nearly two decades, with 16 cases of large whale strandings so far, compiled by the National Oceanic and Atmospheric Administration's (NOAA) Office of Protected Resources.

That is the most strandings in Washington since 1999-2000, when there was a big spike in dead whales all along the West Coast. This season, as then, scientists have counted many emaciated calves among the dead in Washington.

Among the lost so far this season: a 31-foot-long yearling gray whale that was hit by a ship and washed ashore on Thursday, dying hours later. A dead orca calf also washed up in Ocean Shores over the weekend.

Jessie Huggins, of the Cascade Research Collective in Olympia, did a full necropsy on the orca Sunday morning. She said genetic analysis will determine within a few weeks if the baby was a member of the southern-resident orca pods, critically endangered and so far with no successful pregnancies for the past three years.

The infant calf appears to have died from a trauma during birth, Huggins said.

As for the gray whale, it probably was healthy before it was struck by a ship, likely three to four weeks ago judging by the amount of healing that had occurred at the wound, where four vertebrae in its back were shattered, said Huggins, who also did a necropsy of that animal. But the whale after it was struck was not able to swim normally to feed and was badly emaciated when it washed ashore.

"I'm glad it was quick at that point, for the animal's sake," she said.

"This is definitely a high mortality year for grays," said John Calambokidis, of the Cascadia Research Collective. But it is nothing like the losses in 1999-2000, when the population appeared to reach carrying capacity and 651 grays died from Mexico to Alaska.

The cause of the gray whales' troubles this year is not yet understood, Calambokidis said. "The picture is still emerging."

David Weller, who runs the gray-whale monitoring program for NOAA out of its Southwest Fisheries Science Center in La Jolla, Calif., said long-term data collected by the agency shows the big picture for grays is actually good.

"What is going on this year is not overly alarming to me," Weller said. "It is of interest; we are keeping an eye on it. But based on what we have seen, go through in the past, the ups and downs and changes over time, they do just carry on, and the population continues to grow."

The agency's long-term data over the past 25 years has also pointed to a correlation in gray-whale calf survival and the extent of sea ice in the Arctic. "These guys give us a way to peer into the arctic," Weller said. "They are a sentinel species."

If the pregnant females can't get at their food source in the Arctic, it shows in the decline of birthrates the following year.

A second issue plaguing grays and humpbacks this year is entanglement, which has been trending upward, said Kristin Wilkinson, regional stranding coordinator for Washington and Oregon for NOAA Fisheries Protected Resources Division West Coast Region in Seattle.

The average for Washington and Oregon is about three to four whales entangled each year, and this year there have been seven already, Wilkinson said. The increase holds true along the West Coast, said Justin Viezbicke, NOAA's stranding coordinator for California.

Between 2000 and 2013, the average was about 10 confirmed whale entanglements reported per year. In 2017, a total of 31 whales were confirmed entangled off the coasts of California, Oregon and Washington. In 2016, there were 48 confirmed cases and 2015 saw 50 cases, the highest annual totals for the West Coast Region since NOAA Fisheries started keeping records in 1982.

The reasons could be whales following a changing food web closer to shore, as they chase bait fish. It also could be increased fishing pressure with more gear in the water, and even just more reporting of entanglements.

Humans have always been the biggest threat to whales, hunted for their oil, captured for aquariums, even shot for target practice. The protection provided for whales and all other marine mammals under the Marine Mammal Protection Act has allowed for the recovery of most species in the eastern North Pacific and Salish Sea.

Gray whales have rebounded so robustly they were taken off the Endangered Species Act list in 1994.

The major exception is southern-resident killer whales, which remain critically endangered. The annual census reported to NOAA on Sunday by the Center for Whale Research tallies just 75 southern residents, the lowest number in decades.

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Citation: Whale strandings off Washington-Oregon coast highest in nearly two decades (2018, July 4) retrieved 28 November 2023 from https://phys.org/news/2018-07-whale-strandings-washington-oregon-coast-highest.html
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