Dozens of killer whales — including a newborn baby — have been swimming around Vashon the last several days, providing local researchers with several opportunities to learn more about the endangered animals’ diet, health and social behavior.

All 26 members of J pod and some members of L pod have been spotted off of Point Robinson and in Colvos Passage, apparently in pursuit of chum salmon, which are abundant this year. And while it’s normal for orcas to visit central Puget Sound in the fall and winter, their presence this year is especially rewarding to whale researchers and enthusiasts, since last year J pod — a Puget Sound regular — never made an appearance.

“I’m very relieved,” said Ann Stateler, aka Orca Annie, who runs the Vashon Hydrophone Project, which records whale calls and conducts other whale research. “It’s much better than last year. There’s food for them to eat.”

J, K and L pods comprise what’s called the southern resident population of Puget Sound, which was listed as an endangered species by the National Marine Fisheries Service in 2005. Puget Sound was declared the animals’ critical habitat, and now researchers are collecting data in order to put together a recovery plan for the iconic creatures.

This past week’s visit has helped in that effort, said Mark Sears, an independent researcher based in West Seattle who’s been studying killer whales for more than 30 years. For the past several days, Sears and other researchers have been following the whales in research vessels, using large nets to collect fecal matter, mucous and remnants of salmon — items that provide a mother lode of data on the animals and their life cycle.

Fecal matter, for instance, can tell researchers if the whales have parasites, are pregnant or are under stress, said Sears. And the salmon remnants can be used to determine all kinds of details about the orcas’ preferred prey, including the species of salmon, its age and even its natal stream or river.

“They’re like tree rings,” Sears said of the salmon bits.

“We’re trying to fine-tune what’s important to these animals,” he added. “That’s the whole objective here. So every data point is important.”

Brad Hanson, a wildlife biologist with the National Oceanic and Atmospheric Administration, said little is understood about the relationship between orcas and their prey. It’s not known, for instance, how whales determine where their prey is most abundant and how consciously or randomly they figure it out, he said.

“This is one of the fundamental questions we’re trying to address: What’s their relationship to the prey and what motivates their movement in relationship to prey,” he said.

The whales were first spotted off of Vashon last Monday, when a ferry passenger called Stateler with the news, she said. A day later, on Nov. 6, a Whidbey Island resident got a photo of the whales with a tiny, freshly birthed calf snuggled between its mother and brother, a sight that delighted whale conservationists. The whale, dubbed J-43, brings J pod’s population to 26 and the southern residents’ population to 88, the highest in nearly 10 years.

“They seem to be doing pretty well,” Hanson said of J pod.

Since 2000, no members of J pod have died, he noted. And J-4, the mother that gave birth to the newest member, has produced five calves, a very high number for one whale, he said.

But others say the whales’ presence off of Vashon underscores the need to protect and restore Puget Sound and to keep industrial barging and other shipping activity to a minimum.

Last week, after dozens of whales made a dramatic appearance off of Point Robinson, swimming past in close formation, Amy Carey, a whale conservation activist, said she sees their presence as further evidence that Glacier Northwest’s proposed sand and gravel expansion and the huge pier it would build to support the expansion would harm the animals. She stood on the wind-blown point as she talked, her binoculars around her neck, noting the eagle overhead and the frequent splashes made by chum in the slate-gray water.

“The whales essentially show up the same day fishermen do, and they’re not just joy-riding. They’re here for a need,” said Carey, a board member of Preserve Our Islands, the group fighting Glacier’s expansion.

“You have a two-day old orca calf, incredibly fragile, just swim by where there would be an industrial port,” she added. “This is a specific and targeted-use area. It’s not like they’re just passing by.”

Stateler, meanwhile, said she’s concerned by the amount of noise the animals experience as they navigate through central Puget Sound, the most urbanized part of their territory. Last week, when they swam through Colvos Passage, where her underwater microphone is located, she could hardly pick up any of their calls through the sound of boat traffic in the pass.

“It was a wall of noise,” she said.

“We’re always worried about how much noise they’re subjected to, and it was just really bad in Colvos Passage when they were here,” she said.

Later that week, however, it was a different story. On Friday night, the whales again swam through Colvos Passage, and Stateler picked up the best echolocation calls she’s ever recorded — high-pitched, ethereal sounds that delighted her.

She and her partner Odin Lonning stood outside as they passed; it was so quiet, she said, she could hear their blows.

Mimicking the call she heard by way of her hydrophone, she called backed to them.

“It was about as intimate an encounter as you can have with them,” she said. “I knew they were there. And I think they knew we were totally into them being there.”