Harbor porpoises making a comeback in South Sound

Once common throughout Puget Sound, harbor porpoises pulled a disappearing act decades ago. But the small reclusive marine mammal is once again plying the inland marine waters of the state, arousing the curiosity of scientists and waterfront residents.

Earlier this month, 30 marine mammal researchers gathered in Anacortes to share what they know about the population of elusive sea mammmals that reside in the Salish Sea of British Columbia and Washington state.

The meeting was triggered by a kind of good news-bad news chain of events. The good news is that harbor porpoises are reseeding areas of Puget Sound they hadn’t been seen in since the 1940s, including South Sound. The bad news is that the number of harbor porpoises washing ashore dead is on the rise, too.

In 2006 and 2007 some 114 harbor porpoise strandings were reported throughout Washington and Oregon, high enough to trigger what marine mammal researchers call a Unusual Mortality Event. A cause of death was determined for 48 of 81 porpoise carcasses. The main causes were trauma and infectious disease, according to NOAA Fisheries.

Stranding rates have remained fairly high for harbor porpoises in more recent years, noted John Calambokidis, a marine mammal scientist and co-founder of the Cascadia Research Collective in Olympia.

“Maybe the strandings are a result of the increase in sightings,” Calambokidis said. “Or maybe they tell a different story.”

The scientists left the meeting determined to step up research on harbor porpoises. The first order of business is to get a better handle on population size in the inland waters of the state and Canadian province. The last survey occurred in 2002-03, and estimated about 10,680 porpoises in the state’s inland waters.

To aid in the population assessment, Cascadia Research and other participants will use a new research tool called a C-Pod, which is an acoustical device that records harbor porpoise vocalizations.

The group also wants to conduct more research into the strandings. Some of the known causes of harbor porpoise deaths include entanglement in fishing nets and infectious diseases. Navy sonar, contaminants and vessel traffic are other possible contributing factors.

“We are seeing mortality in harbor porpoises from gill net fishing in Puget Sound,” Calambokidis said.

One way to reduce the likelihood of harbor porpoises getting snared in fishing nets is to install small, cylindrical acoustic pinging devices to the gill nets to keep the porpoises away, he said.

Blunt-beaked and stocky, harbor porpoises are 5 to 6 feet long, weighing 135 to 170 pounds. They are gray-brown to black on top and have a white belly. Their triangular dorsal fin is hard to see on the water’s surface unless the waters are calm.

Not very social, porpoises typically travel alone or in groups of two to five. They aren’t prone to displays when they surface to breathe, making them all that much harder to spot. They surface for air about every 25 seconds, and make a puffing noise that sounds much like a sneeze, according to a National Geographic Society fact sheet.

While they can dive deep — roughly 200 meters — they prefer the shallow coastal waters, harbors and bays of the temperate zone of the Northern Hemisphere. They feed on forage fish such as herring and anchovies and larger molluscs such as octopus and squid, according to a fact sheet prepared by NOAA Fisheries.

Harbor porpoises were common in the South Sound in the 1940s. A vessel and aerial survey in 1994 didn’t detect any. But more recent surveys in 2009-10 found harbor porpoises throughout Puget Sound, suggesting a return of animals to this region.

Eld Inlet resident Kim Merriman keeps a keen eye trained on her watery front yard, It’s not unusual for her to see harbor seals, river otters and harbor porpoises all in the same day.

“There seems to be more harbor porpoises in recent years, and in the last several months, I’ve been seeing them almost every week,” she said. “It’s always a thrill.”

The sightings are often associated with schools of bait fish, she said, suggesting they may be chasing prey.

“I usually see them in groups of three to five,” she said. “But six weeks ago, I saw 10 heading into Eld Inlet.”

Merriman keeps a log of her sightings that she shares with Cascadia Research. Anyone spotting marine mammals in South Sound is encouraged to report their sightings to Cascadia at 360-943-7325. John Dodge: 360-754-5444 jdodge@theolympian.com