People on or near the water are being asked to keep a look out for a killer whale calf carcass thought to be floating somewhere around the San Juan Islands.

If found, the dead calf could provide important clues to help scientists determine why Puget Sound’s population of killer whales has declined precipitously—and what might be done about it.

“We want people to know that if they find (the calf), we definitely want to know about it,” said Joe Gaydos, chief scientist for the SeaDoc Society, an organization working to improve marine ecosystems in Puget Sound.

A boater spotted the dead calf on Sunday floating off Lawrence Point near Orcas Island and reported the sighting over his marine radio, saying that the calf still had its placenta attached. The information was relayed to the Marine Mammal Stranding Network, which investigates reports of stranded marine mammals. Network staff searched the area the calf was reported to be seen but weren’t able to find it.

A subsequent report indicated the calf might be off the north end of Blakely Island, but it turned out to be a porpoise. The search continued Wednesday off the north end of Lummi Island after a report that the calf was spotted there.

Anyone who sees the calf is asked to contact the San Juan County Marine Mammal Stranding Network at 800.562.8832. The Network recommends that the carcass be tied to a boat fender or other object so it will be easier to find.

Whale carcasses provide valuable research potential but are rarely recovered, Gaydos said. Scientists missed an important opportunity last year, when a dead killer whale washed up on Henry Island, just off the northwest shore of San Juan Island. By the time a report was made several days later, the carcass was too decomposed to conduct much testing, but researchers were able to confirm that the calf was an aborted fetus from the Southern Resident killer whale population of Puget Sound.

“Only about 10 percent of the resident killer whales that die are ever found,” Gaydos said. “Our ability to necropsy (conduct an autopsy on) a dead killer whale gives us a huge insight into how it died and the factors that are causing them to die.

“Are there diseases that are causing problems? Are these animals dying because they’re starving? If you don’t find the body, it’s really hard to know what happened.”

The Southern Resident killer whale population that frequents the water of Puget Sound and the San Juan Islands has shrunk in recent years. Scientists have attributed the decline to increased disease, interference from ships and a reduction in Chinook salmon, the whales’ preferred food source. In earlier decades, the whales were killed or captured for use in aquariums.

Scientists estimate there were once around 200 killer whales in the region; that number has declined to fewer than 90. The state’s killer whales, also known as orcas, were declared endangered by the federal government in November 2005.

In June of this year, the National Ocean and Atmospheric Administration proposed new rules that would prevent vessels from coming within 200 feet of killer whales or parking in the path of a whale. Additionally, the proposed regulations would establish a half-mile zone along the west side of San Juan Island from May 1 through the end of September that vessels would be prohibited from entering. The rules could take effect next May.

If the calf spotted on Sunday is found, it will be tested for various types of diseases and samples will be sent to researchers worldwide for additional analysis. The results will be shared among scientists in numerous countries, Gaydos said, with the view of collaboratively piecing together a theory about how the animal died.

Gaydos said his research has identified only about a dozen diseases that killer whales are known to have contracted. The rest remain a mystery, making it challenging for scientists to determine the range of factors contributing to their decline.

“We realized that we really don’t know a lot about what goes on with killer whales, and that’s probably because most of the ones that die don’t get found,” Gaydos said.