Conserving Alaskan Waters: Monitoring for Invasive European Green Crabs

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It was a fine cloudy morning with a touch of fresh breeze on June 11th; just another typical morning here in Sitka. My supervisor, Conservation Science Director for the Sitka Conservation Society (SCS), Scott Harris arrived at the Forest Service Bunk house (where I live) at 6:45 a.m. to pick me up. All I was told is that we will be setting traps to look for an invasive crab species that could potentially reach the waters of Alaska. I was super excited since I am not at all familiar with trapping crabs. On our way, we stopped to pick up Bethany Goodrich, SCS's Tongass Policy and Communications Resident. Our first stop was at the Sitka Sound Science Center and Taylor White, the aquarium manager, greeted us. We loaded small containers with dead herring fish as bait before placing these containers into the six crab pots.

At 7:30 am in the morning, members of the Sitka Conservation Society and Sitka Sound Science Center were already busy, loading the boat with crab pots, and getting ready to take off to Sitka Sound to monitor the waters of the invasive crab species, the European Green Crab. As SCS's Salmon Conservation Intern, I was eager to learn about the methods of monitoring invasive species in Alaska.

Scott prepares to plunge the first anchor into the water.

Currently, the European Green Crab is not known to occur in Alaska, but are currently found as far north as British Columbia.European Green Crabs first entered the United States in the mid 1800's, coming by sailing ship to the Cape Cod region.Since then, the crabs have become well adapted to the environment and flourish in the waters of United States. However, with the increase in numbers, European Green Crabs have created negative impacts on local commercial and personal fishing and caused habitat disturbance thus affecting other native species. These crabs heavily prey on tubeworms, juvenile claims and juvenile crabs. In recent years, with the increase in the European crab population, there has been a strong decline in the populations of young oysters and other smaller native shore crabs. With its increasing population European Green Crabs have the potential to outcompete the native Dungeness crab for food and habitat. Thus, our mission of setting up the crab pots is to capture and halt the invasive European Green Crabs as early as possible in their invasion.

Shortly after we finished placing the bait, we headed towards Scott's boat, Alacrity and placed the baits while waiting for Lynn Wilber, a PHD student from the University of Aberdeen in the United Kingdom. Once Lynn showed up, we headed out to the sea. As we headed out to sea, the panorama before me reminded me of the scenes from the discovery channel's series "Deadliest Catch", except for the fact that the water that we were in was a lot calmer.

We went out to where the water depth was about 30 ft and Scott plunged the first metal anchor that was attached to a marker buoy into the water. Attached to the buoy was a long heavy rope line and on that line we attached the crab pots using metal clippers. Each crab pot has to be 5-arm length apart from the other. One by one, we deployed the crab pots in to the water and at the end of the line, we attached another anchor with a marker buoy attached to it.

One of the sea stars we encountered.

The next day, around the same time, we headed out to the sea to see if we had captured any European crabs in our crab pots. Keeping with the protocol, we had left the traps for the whole 24 hours. As we pulled in each trap, we discovered a bunch of sea stars, 1 rockfish and a male and a female Kelp Greenling and luckily no European Green Crabs. As part of the protocol, we also measured the salinity of the water because this is an area where the freshwater from Indian River fuse with the ocean and thus the salinity can fluctuate from time to time. Another reason for measuring the salinity is that the European Green Crabs are known to be tolerant of freshwater. Thus it is important to monitor the water chemistry, to determine if it is suitable environment for European Green Crabs to become established.

This process of monitoring happens every month in an effort by the staff of Sitka Conservation Society and Sitka Sound Science Center to protect that valuable native species of Alaska and to stop the invasion of the European Crab species as soon as possible. Forests, streams and the ocean all combine to provide a favorable habitat for salmon. To keep our fisheries healthy, we must continue to monitor and implement restoration projects in all of these three areas.

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