HARBOUR PORPOISES BACK, BIG TIME
Scientists aren’t sure why exactly, but it may be due to decline in gillnet fisheries, or a sign that the area cleanup is working
SEATTLE — After nearly disappearing from local waters for decades, harbour porpoises are once again a common sight in Puget Sound.
“They are back, big time,” said biologist John Calambokidis with the Cascadia Research Collective in Olympia. “They are probably the most common cetacean in Puget Sound.”
Common in U. S. inland waters through the 1940s and ’ 50s, harbour porpoises virtually disappeared in Puget Sound south of Admiralty Inlet and Hood Canal by the early 1970s.
Entanglement in gillnets, which drowns the air- breathing mammals, vessel noise, and contamination from industrial pollution are all possible culprits, pushing the animals farther north in their range, researchers posit.
But beginning around 2007, the sight of porpoises through the waters of Puget Sound has become common once again. In calm conditions, the animals can be seen everywhere from the Mukilteo ferry dock, to Burrows Pass near Anacortes, to the waters of west Seattle.
Just why isn’t known, but it could be from declines in gillnet fisheries in Puget Sound, as well as ongoing cleanup efforts that have reduced industrial sources of pollution .
Phocoena phocoena is a distinct species unique to Puget Sound’s inside waters. They live out their lives foraging herring, smelt and sand lance in shallow nearshore waters. Living 15 to 20 years, females produce a calf each year for most of those years.
According to a natural history of the harbour porpoise by Joe
You can’t protect something unless you know something about it.
AILEEN JEFFRIES
PRINCIPAL INVESTIGATOR
Gaydos, chief scientist with the SeaDoc Society, a non- profit marine- conservation science program at University of California, Davis, harbour porpoises are the smallest of 22 species of cetaceans in the Salish Sea and probably one of the few that are resident yearround.
Scientists have been taking more notice of harbour porpoises of late. A research conference convened on the harbour porpoise in February drew interest from state and federal agencies, as well as non- profits around the region.
The Pacific Biodiversity Institute, based in Winthrop, Okanogan County, has taken up the cause of the porpoise, advocating for its use as an indicator species of the health of Puget Sound.
Volunteers with the Skagit County Beach Watchers are tracking sightings from headlands, recording porpoise sightings for the institute in two- hour intervals. And the biodiversity institute has deployed two acoustic monitors to track the animals, using buoys to observe harbour porpoise travel paths.
Already, the recorders, which pick up the animals’ distinctive sounds of echolocation, have detected that the porpoises keep to a schedule: about twice as many pings are detected at night, beginning about 6 p. m., until 6 a. m., says Aileen Jeffries, a retired physicist and principal investigator for the institute’s harbour porpoise project.
“If you think about it, it’s an incredible world, they live in an acoustic world, whereas we live in a visual world,” Jeffries says. “It is fun learning about another creature, it’s humbling.”
She points out that the last population survey, counting about 10,680 porpoises in Puget Sound, is out of date, occurring in 2002- 03.
“We want to set a baseline as a way to follow trends in the population that can be used to realistically assess the stability of the harbour porpoise in Puget Sound,” Jeffries says. Such data could even be used to evaluate the prospect of creating more marine reserves in the sound.
“You can’t protect something unless you know something about it.”
Scientists also are concerned about a spike in strandings, Gaydos says. A stranding is any occasion in which a marine mammal is on land, dead or alive, such as on a beach, on rocks, or a boat ramp or marina.
Until the mid- 2000s, statewide annual harbour porpoise strandings were rather consistent, at an average of six animals. But strandings have climbed since then, more than tripling, for reasons that remain unclear.
“Is that just because the population is increasing?” Gaydos says.
“Or is there something else going on? Here, too, a new stock assessment from NOAA, which monitors marine mammal populations, is needed.”