Killer whale filmed swimming with porpoises identified as Old Thom

CHATHAM — On Sunday afternoon, fishermen on a boat from Got Stryper Charters were looking for tuna 50 to 70 miles east of Chatham when they filmed a killer whale swimming with a pod of five or six porpoises just off the bow of their boat.

“It was breathtaking,” captain Kelly Zimmerman said. “My mind was completely blown. There was a lifelong (tuna) harpooner on the boat, and he said in all the years that he had been doing it, he had only ever seen orcas two other occasions.”

Zimmerman said the orca followed alongside the boat for 20 minutes.

Video: Orca spotted swimming off Chatham

Killer whales are occasionally seen off the Cape's coastline. A pod of killer whales was spotted off Chatham in August 2016.

Zimmerman said they had noticed a lot of other marine life before encountering the orca, including whales and basking sharks. He said Charlie Whitcomb, another charter captain in the West Chatham-based business, was the first on board to spot the whale.

The group noticed some splashing and went over to investigate and saw the killer whale swimming alongside the porpoises.

This was the first orca any of them had ever seen, Zimmerman said.

Tara Stevens, a Ph.D. candidate at the University of Rhode Island’s Graduate School of Oceanography, said in an email that killer whales in the northwest Atlantic have been known to venture close enough to land that they can be seen from shore. While it is rare to see one, the population between Cape Cod and Canada is believed to number around 200 individuals.

Stevens identified Sunday’s orca as Old Thom, a whale who has been seen regularly in Canada and off the Cape. Old Thom is not actually all that old, maybe 12, and the name refers to a killer whale that existed in the early 20th century. This orca is most often seen alone, Stevens said, and it is believed he frequents the Gulf of Maine during the summer.

“We have definitely seen him before, going back a decade at least,” Stevens said. “He seems to be one of the only (killer whales) regularly sighted here.”

Another identifying trait of this orca is his habit of being seen swimming with porpoises, Stevens said. Although it is not common for killer whales to do so, Stevens said this would show that this whale does not typically prey on porpoises and might be after the same food: “small schooling fish, or even tuna.”

Orcas can be found in all the oceans around the world, but particularly off British Columbia or Washington state, Southeast Alaska, Antarctica, Iceland, Norway and Newfoundland or Southern Labrador, Stevens said.

She does not expect orca sightings will become a common occurrence, although they were seen with some regularity a few decades ago when there was more tuna in the Gulf of Maine.

She said she hasn’t heard of any sightings of females or calves recently in this area and she doubts they will become a fixture such as seals and great whites.

“But killer whales are highly mobile and can travel great distances in a short period of time, so that could certainly change,” Stevens said.

— Follow Edward Sutelan on Twitter: @EdwardSutelan.