Scientists still following whales that swam through oil spill

Oct 21, 2021

The Chugach Transients have not had a calf since the Exxon Valdez Oil Spill in 1989. And scientists aren't exactly sure why.
Credit Courtesy of Dan Olsen / North Gulf Oceanic Society

Scientists in Homer and Seward have spent the last several decades tracking a population of mammal-eating killer whales called the Chugach Transients in the Gulf of Alaska.

There used to be 22 whales in the pod. But the year after they swam through the Exonn-Valdez oil spill in 1989, nine members died. Others went missing.

“And now there are seven of them remaining," said Dan Olsen, a field biologist with the Homer-based North Gulf Oceanic Society.

Olsen and his team have been keeping track of all seven members of the Chugach Transient pod as they age. Late this summer, researchers were still waiting for a glimpse of the seventh transient — a 46-year-old lone male named Egagutak.

“It wasn’t until late in the season that one of the local tour companies here in Seward sent us a photograph and we were able to confirm that this male was still alive," Olsen said. "He’s 46 years old now, so we may not have him much longer. Males often live to be 45 to 50 years old. So every year that goes by, we’re crossing our fingers that he’s still alive.”

The North Gulf Oceanic Society identifies the transients photographically. It also tracks them acoustically, since pods have distinct calls.

Olsen recorded that lone male’s call in 2019:


 

He said the distinct call is one call he’s hearing less and less, as the population of whales dwindles.

The Chugach Transients have not had a calf since the oil spill, over 30 years ago. Olsen said scientists are not exactly sure why.

Other populations of killer whales are doing well. But two pods that swam through the spill are not.

“It’s difficult to know why, if the oil spill reduced their prey abundance such that they weren’t able to have enough nutrition to continue to have offspring, or if the contaminants directly impacted their reproductive systems," he said. "But regardless, we’re seeing a population that is going extinct.”

Olsen said it’s important to keep tracking the whales because it helps researchers track the entire ecosystem.

“Killer whales are an apex predator and often are indicators of the health of the entire ecosystem," he said. "And changes in their population, changes in their body condition, their body health, can help alert us to issues that we’re seeing in the ecosystems.”

The North Gulf Oceanic Society has been around since the 1980s and is based in Homer.

Historically, it has relied on funding from the Exxon Valdez Oil Spill Trustee Council, the group tasked with spending the $900 million civil settlement from the Exonn Valdez oil spill. This year, Olsen said, the council decided it will not continue funding the group’s research going forward.