Washington’s reintroduced fisher populations doing well, but biologist says work isn’t over

The work to restore fishers to Western Washington seems to be paying off, with the small carnivores exploring new habitat and finding a way to make a living in places where they were once trapped to extinction.

Jeff Lewis, the Washington Department of Fish and Wildlife’s top fisher biologist, said there are positive signs for the agency’s restoration efforts in the north and south Cascades and in the mountains of the Olympic Peninsula.

But he also said it’s too early to claim absolute success – even in the Olympics, where reintroduction began almost 18 years ago.

“It doesn’t feel like we’re there yet,” Lewis said. “But it does feel positive.”

Fishers, a mid-sized member of the weasel family, were once widespread in the western portion of the Lower 48. They were found in northeast Washington, the Cascades and the Olympics.

They were decimated by trapping and habitat destruction in the late 1800s and early 1900s. By the middle of the 20th century, they were effectively gone.

Surveys were done throughout their historical range in the 1990s but turned up no sign of them, according to WDFW. Federal protections have never been granted, but fishers were listed as a state endangered species in 1998.

Reintroductions have long been known to be effective at restoring the species. Idaho first reintroduced them in the 1960s. Montana did so in the 1990s. Washington got into the game in the 2000s.

The efforts started on the Olympic Peninsula, where biologists knew there was good habitat for the mustelids. Lewis said about 90 fishers were brought in from British Columbia between 2008 and 2010, and that more were added from Alberta later to boost genetic diversity.

Occupancy surveys initially showed the animals were staying outside of Olympic National Park. Lewis said that was concerning because they thought most of the best habitat was in the park’s interior.

Some time later, however, a graduate student studying martens in the park confirmed the presence of fishers in the interior.

“With those fishers being found in there, it makes it seem like they are more widely distributed and more stable,” he said.

Still, he’s watching population trends closely to ensure they continue on a slow positive growth trend.

Reintroductions in the Cascades took place from 2015 to 2019. A total of 81 fishers were placed in the southern Cascades and 89 were put in the North Cascades.

In the southern Cascades, follow-up surveys showed the fishers have “pretty good distribution” from the Columbia River to Interstate 90, Lewis said.

In the northern part of the range, the distribution is more patchy, which he said is at least partially because the habitat itself is patchy.

He added that an analysis of the areas fishers use in the Cascades is coming, and that it will help identify what kinds of habitats the animals like.

Dave Werntz, senior director for science and conservation at Conservation Northwest, has been following the fisher work for years. He said it has been successful in terms of establishing populations in places where they’d disappeared.

Now the work Lewis and others are doing is about making sure the populations persist.

“What that information is going to tell us is the long-term sustainability of the population,” Werntz said. “We’re evaluating how strong that population is and how sustainable that population is.”