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B.C.: When Wayward Whales Strand |
| August 3, 2005 |
By Ally McNaughton, AquaNews Correspondent
 | Vancouver Aquarium staff tend to 'Tyee,' a juvenile gray whale that stranded live and was successfully refloated near Vancouver on May 25, 2005.
Photo: Sheryl Barber |
Whales strand for different reasons, scientists say, and while a stranding could mean many things, it is not necessarily a sign of dire times for whales. North Pacific gray whales have one of the longest migrations of all marine mammals, moving annually between their winter breeding grounds in Baja, Mexico and the summer feeding grounds in the Bering and Chukchi Seas, Alaska.
Scientists expect some mortality to occur along this migration route, and at least one whale expert insists that even the spate of strandings in early summer of this year is no cause for alarm.
"Initially, I was a little worried that it might be another drastic year for the gray whales because of the frequency of strandings in a short time period," said Dr. Volker Deecke, a whale researcher at the University of British Columbia and a Vancouver Aquarium Research Associate. "This kind of mortality that we saw this year was a little high, but still not beyond what you might expect in a migrating population of this size, and nothing like what was reported in 1999-2000."
In 1999-2000, nearly 200 strandings were reported along the migration corridor, contributing to a dramatic decline in the eastern North Pacific gray whale population. Evidence has since linked those strandings to an unusually late ice melt in the Bering Sea during the previous spring, which significantly shortened the summer feeding season. This year, at least three northbound gray whales have already stranded in British Columbia and as many as ten in Washington State. Most were found in a similar condition: emaciated and showing signs of malnutrition.
Fueling Up
Like marathon runners who load up on carbohydrates before a big race, North Pacific gray whales have one major source of food during their entire round trip journey: the summer feeding grounds in Alaska. Anything less than an abundant supply of plankton and invertebrates in the Bering and Chukchi Seas may leave the whales undernourished and unable to complete the return journey the following year. Furthermore, malnourished whales often take risks in an effort to regain their strength and energy.
 | Photo: Doug Sandilands | There She Blows!
On June 13th, a gray whale was sighted twice by whale-watchers near Telegraph Cove. After examining photos taken at the time, experts believe the whale is almost certainly 'Tyee,' the gray whale that stranded in Tsawassen in early May. It was resighted a few nights later near Telegraph Cove and appears to have made a full recovery.
If you see a stranded whale or a marine mammal that might need rescuing in B.C., call the Marine Mammal Rescue and Rehabilitation Centre at (604) 258-7325. |
Deecke says 'Tyee,' the young gray whale that stranded during low tide in Boundary Bay, was in an area where gray whales are not regularly sighted. But after last year's relatively normal feeding season in the Bering Sea, it remains unclear why the whales are running out of fuel this year.
A Tangled Web
Deecke's early fascination with gray whales was sparked by the lack of attention these "ugly ducklings" receive compared to some of the more charismatic whales on the B.C. coast, such as orcas. He believes gray whales live continuously on the edge of their energy limits because of their lengthy migration.
During this grueling journey, any number of events could trigger a dangerous domino effect of nutritional stress, risky feeding behaviour, and stranding. Gray whales' preferred feeding habitat – shallow, inshore waters – brings them into contact with humans, boats and fishing gear more frequently than other whales. In fact, both Tyee and another gray whale that stranded along the B.C. coast this summer bore scars from entanglement by fishing gear. On one of the whales, rescuers observed deep wounds that could only have come from a ship strike.
An entangled whale often feeds with difficulty and is forced to spend extra energy swimming and struggling to free itself. On the long journey to Alaska, these 'unbudgeted' expenditures of energy can quickly lead to malnutrition and emaciation. Furthermore, an entangled whale may not be agile enough to avoid an often-fatal ship strike.
"Having evidence of two animals that have stranded now, with (scars from) recent entanglements, makes me think that it is an issue that we need to be aware of," Deecke said. "I'm optimistic that with enough awareness and working with the fisherman, new and simple modifications could be made to the gear, like a cotter pin that breaks to release the line."
| Ally McNaughton is a marine biologist whose research focuses on kelp forest ecology along the B.C. coast. As a research diver, she has contributed to studies on diver impacts on populations of black-eyed gobies. Ally is happiest when underwater. |
Lobster fisheries on the East Coast are implementing these 'quick-release' lines, which break easily if a whale becames entangled in the rigging that holds the traps together, and Deecke feels that similar technology could work well in crab pots on the West Coast.
While entanglement is only one thread in the complex web of nutritional stress, its prevalence underscores the importance of protecting key habitat off the B.C. coast, where malnourished whales often stop to refuel during their migration. Part of Deecke's work – and the work of organizations such as the B.C. Cetacean Sightings Network – is to identify these important migration points.
This research, combined with the use of 'whale-friendly' crab pots in the inshore waters of the B.C. coast, could substantially reduce the risk of entanglement to migrating North Pacific gray whales. These developments make Volker Deecke optimistic about their future. "Chances are," he says, "these animals may just need to get that extra push to allow them to complete their migration and make it to the feeding grounds."
| Source: Vancouver Aquarium Marine Science Centre |
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