Invasive slug species in Girdwood may be on the move; experts ask public for help tracking

PALMER, Alaska (KTUU) - An invasive species of mollusks, typically found in Southeast Alaska and established in Girdwood in 2015, have been reported in the Anchorage Bowl this year, according to integrated pest management technician for the Matanuska Experimental Farm and Extension Center Joey Slowik.

“The European black slug is not necessarily new to Alaska,” Slowik said. “It was introduced into Cordova about the 1980s and it really stayed there for a long time.”

Slowik said the slug population eventually worked its way into Southeast Alaska before establishing itself in Whittier — likely transported by fishing vessels — before landing in Girdwood eight years ago.

“We’ve gotten reports from all over Prince William Sound on a lot of the remote islands, unfortunately, where people probably [are] stopping and having lunch, not realizing that there’s a slug in their anchor line or something like that and they throw out their anchor line, the slug hops off and moves on,” Slowik said.

According to Slowik, individual reports of the large specimen being seen in Anchorage have been received since the early 2000s, but the species has yet to establish itself in the area. However, with a number of reported sightings in the Anchorage Bowl this year, the concern comes from the slug’s hermaphroditic nature, meaning they produce both male and female gametes and can reproduce rather quickly.

The species can lay 50 to 100 eggs at a time and continue to lay eggs for extended periods of time. Slowik said Alaska is a “slug habitat” because of the damp and cool climate, which has been the case in Anchorage this summer so far.

However, slugs are nocturnal by nature and typically go into a dormant period around June because of all the daylight.

“They just sort of like emerge in the spring, disappear, and then they reemerge come end of July, August,” Slowik said. “It’s cool, it’s damp, and it’s getting dark and they like that.”

Slowik said there’s little data on the effects the slug has on Alaska’s ecosystem, but that the species has been known to be destructive garden and agricultural pests in other places they’ve been introduced.

European black slugs can grow anywhere between two and five inches in length and have a feather-like characteristic on their lower end, whereas native slugs are all smooth. Residents are being asked to report sightings of the slugs on the pest reporter website, as well as encouraged to eradicate the mollusks if possible.

“Right now we’re just sort of learning a bit about where they are occurring, where they’re establishing themselves, and the numbers and the lifecycle,” Slowik said.

Editor’s note: This article has been updated to provide clarification that Cordova is not a part of Southeast Alaska.