3 Bumps5 spines

Picture by John Southern

The green crab’s distinguishing features are 5 spines, or teeth, on each side of its fan shaped shell and 3 rounded lobes between its eyes. The two backmost legs are flattened. The abdomen (underside) color ranges between green, orange, and red, and the dorsal (top) side of its shell is a mottled dark green with yellow patches.

Why are they a problem?As their name suggests, this species is native to

European waters. Over time it has been introduced to multiple new habitats, including

the Atlantic and Pacific coasts of North America. Although green crabs have been detected only

as far north as Vancouver Island in British Columbia thus far, models indicate that the

species will be able to survive in coastal Alaskan waters. European green crabs are aggressive

predators, eating clams, mussels, marine worms, and crustaceans that are important

foods for native marine animals. If green crabs invade Alaskan waters, they could be a serious

threat to native crabs and fisheries.

What is a tunicate?Tunicates, or sea squirts, are marine invertebrates (lacking a back bone) that grow attached to surfaces. They might be confused with a sponge, but they are more resistant to touch. They can range in color, including orange, red, yellow, black, translucent, cream, and blue. They can be

solitary (completely independent and generally fairly large) or colonial (congregations of zooids that aggregate by budding, like corals). Tunicates filter feed by siphoning plankton from the water. Tunicates belong to the Phylum

Urochordata, which are more closely related to vertebrates (including humans) than any other

invertebrate group. There are a number of native species in Alaskan waters; however, several non-native species

have been detected.

Invasive tunicates documented in Pacific waters: Botrylloides violaceus, Botryllus schlosseri, Styela clava, Didemnum sp., and Ciona intestinalis.

Why are they a problem? Tunicates are a fouling organism that can smother other marine

organisms and coat surfaces, such as boats and docks. They filter out the water’s phytoplankton, thus depriving other species of their

nutrition. Since larval tunicates can be transported in ballast water and adults can foul boat hulls, tunicates can easily disperse to new waters,

where they can readily establish in the absence of natural predators. In the coastal Pacific waters of North America, the Smithsonian

Environmental Research Center (SERC) coordinates a monitoring program ranging from Tijuana Slough, CA to Port Valdez, AK.

Smithsonian Environmental Research Center (SERC)

National Park Service

U.S. Department of the Interior

Glacier Bay National Park and Preserve

Marine Invasive SpeciesMonitoring Program

What is an invasive What is an invasive species?species?

Invasive species come from other

parts of the world and can be harmful to the environment,

natural resources, humans, and the economy. Invasive species are transferred between regions

by people intentionally or accidentally. For marine invasive species, common forms of transfer

include ship’s ballast water, hull fouling, and aquaculture.

"Invasive species have large effects on native biodiversity, cause hundreds of billions of

dollars in economic damages, and complicate the management of natural ecosystems around the

world." (Strayer, 2006)

What is an invasive What is an invasive species?species?

Invasive species come from other

parts of the world and can be harmful to the environment,

natural resources, humans, and the economy. Invasive species are transferred between regions

by people intentionally or accidentally. For marine invasive species, common forms of transfer

include ship’s ballast water, hull fouling, and aquaculture.

"Invasive species have large effects on native biodiversity, cause hundreds of billions of

dollars in economic damages, and complicate the management of natural ecosystems around the

world." (Strayer, 2006)

04

812

San Deigo

Long Beach

San Francisco Bay

Humboldt Bay

Coos Bay

Puget Sound

Ketchikan

Sitka

PWS

Kachemak Bay

Kodiak Island

Dutch Harbor

Mean Number of Non-Native Tunicates

04

812

San Deigo

Long Beach

San Francisco Bay

Humboldt Bay

Coos Bay

Puget Sound

Ketchikan

Sitka

PWS

Kachemak Bay

Kodiak Island

Dutch Harbor

Mean Number of Non-Native Tunicates

Botrylloides violaceous (orange morph) – an invasive colonial tunicate. SERC

Ciona intestinalis – an invasive solitary tunicate. SERC

What aboutWhat aboutGlacier Bay?Glacier Bay?

So far, no invasive green crabs or tunicates have been detected

in Glacier Bay through our monitoring efforts. For green crabs, we set out traps once a

month during the summer in the lower intertidal area of Bartlett

Cove. For tunicates, we suspend settlement plates from

our three docks quarterly to detect whether any tunicates colonize the surfaces. Atlantic Salmon are the only marine

invasive species detected within park waters to date. We will continue collaborating with partner agencies to detect marine invasive species.

What aboutWhat aboutGlacier Bay?Glacier Bay?

So far, no invasive green crabs or tunicates have been detected

in Glacier Bay through our monitoring efforts. For green crabs, we set out traps once a

month during the summer in the lower intertidal area of Bartlett

Cove. For tunicates, we suspend settlement plates from

our three docks quarterly to detect whether any tunicates colonize the surfaces. Atlantic Salmon are the only marine

invasive species detected within park waters to date. We will continue collaborating with partner agencies to detect marine invasive species. For more information: Whitney Rapp, Invasive Species

Coordinator, Glacier Bay National Park and Preserve, Gustavus, AK 99826 – whitney_rapp@nps.gov, 907-697-2603

What should you do if you find one? If you find a green crab, don’t throw it back in the water! Keep it in a container with information about where and when you found it. Then put it into a freezer

or preserve it with alcohol. Contact 1-877-INVASIV for more information.