ADF&G Plans eDNA Detection for Invasive European Green Crabs in Southeast Alaska

None have been spotted yet in the waters of Southeast Alaska, but the alert is on for European green crabs, one of the most invasive species in the marine environment.

Linda Shaw, invasive species coordinator for the Alaska regional office of NOAA Fisheries, said her office had already formed partnerships to monitor these voracious crustaceans, who devour juvenile king crab as well as juvenile salmon. They also destroy eelgrass habitat where larval fish hide from predators and outcompete Dungeness crab for food and habitat.

NOAA Fisheries biologists say alarm bells went off in Alaska after natural resource managers in British Columbia discovered several adult male and female European green crabs on the archipelago of Haida Gwaii, off the coast of Prince Rupert this past July. The European green crabs introduced to North America in the 1800s, likely traveling in ballast water of merchant ships from Europe and were first detected in the San Francisco Bay area in 1989. The species is actually native to the northeast Atlantic Ocean and Baltic Sea.

Shaw and Alaska Sea Grant Fellow Meredith Pochardt decided on a plan to use environmental DNA or eDNA to detect the possible presence of these crab in Alaskan waters. They collaborated with invasive species researchers from Washington state and British Columbia on a monitoring design or trapping combined with eDNA water sampling. DNA (deoxyribonucleic acid) is the molecule containing the genetic code of organisms and the cellular material shed by organisms into the environment is eDNA. The plan is to collect seawater from various locations around Alaska and test it for genetic material from European green crab.

The project was delayed when the novel coronavirus hit Alaska, but through their partnership with the Alaska Department of Fish and Game, Shaw and Pochardt were able to help scientists at the Alaska Fisheries Science Center obtain the tools needed.

As time allowed NOAA research fish biologist Charlie Waters at AFSC and his research partner, Dave Nicolls, were finally able to set traps at the Little Port Walter Research Station on the southeastern tip of Baranof Island in late October, using specialized fish traps. When they pulled the traps they found sculpins and Pacific cod but no European green crabs.

Once the eDNA from the water in that one round of sampling is examined, they will know more, and they hope to continue their efforts next season.

The 2020 sampling effort will provide baseline data on the presence of European green crab in southeast Alaska and planning is underway to continue monitoring for this voracious invasive species in 2021 The monitoring program also includes Ketchikan, Juneau, Cordova, Valdez, Tatitlik, Whittier, Chenega Bay, Homer, Seward, Kodiak and Dutch Harbor.