Is That Crab Native or Invasive?

Friday, May 11, 2018 by Natasha

https://upload.wikimedia.org/wikipedia/commons/thumb/9/90/Rock_crab_on_tunicate_colony.jpg/256px-Rock_crab_on_tunicate_colony.jpgWith spring finally here and summer on its way, you might be spending more time outdoors, and if you find yourself at Maine’s coastline, hopefully you are doing one of my favorite activities: tidepooling! When you explore tide pools, you most likely will spot some juvenile crabs or even crab molts. But is it a native species, or an invasive species?

A very common native crab here in Maine is the rock crab, which spends the majority of its life along the shoreline. Like other crabs, the rock crab is able to breath underwater, but can also breath out of water for long periods of time, which is a useful adaptation for this species that spends its time where the tide comes in and out. You can spot the rock crab because of its reddish-brown, smooth oval or fan shaped carapace.

One of the invasive species here in Maine is the European Green Crab, which is believed to have arrived in the 1800s inside of the ballast water of ships. These crabs have a narrow carapace with a set of five spines on each side, and have a green-dark brown/black color. Green crabs are considered invasive because they feed on native shellfish in the Gulf of Maine like blue mussels and soft-shell clams.

If a species is transported to a new place but does not cause harm to native species, it is considered “non-native” instead of “invasive.”  To learn more about native, non native and invasive species check out this vital signs page!



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