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Not all invaders…

Discover the impact of invasive species in Boston Harbor, specifically the European Green Crab and Asian Shore Crab. Learn how these invaders disrupt ecosystems, threaten native species, and cost millions in damages. Become a citizen scientist and help identify these invasive crabs to protect our environment.

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Not all invaders…

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  1. Not all invaders… come from outer space…

  2. Curley School Boston Harbor

  3. Invasive Crabs in the Boston Harbor

  4. Invasive crabs are “exotic” not this kind of exotic…

  5. Exotic species are not native to the ecosystem Exotic species can be animals, plants, or even microbes (microscopic!) Meaning we’re not originally from here

  6. Where are we from? Imagine life without these things! Chickens? Apples? Rice? Cows?

  7. So, how do exotics get here? We introduced some of them on purpose Fact: Over 98% of the U.S. food supply are introduced plants/animals

  8. Or… We introduce them accidentally For example, ballast water is used to stabilize the ship… These exotics get dumped into local waters. Ballast water line but can transport a huge aquarium of exotic life!

  9. Exotic Disaster

  10. When is an exotic invasive? When it spreads rapidly and out-competes native species A Kudzu invasion blankets all other life

  11. Invasive success: They have HIGH reproductive rates A single female Asian Shore Crab can produce up to 200,000 eggs per year! That’s twice the rate of native crabs

  12. Invasive success: They leave behind their predators and competitors. They play by a different set of rules. Wild boar in the U.S.

  13. Invasives can be harmful… • They threaten biodiversity • Fact: ½ of all species that are “endangered” have been impacted by invasives Many of these endangered species become extinct

  14. Natural ecosystems support a biodiversity of species The arrival of an exotic like Purple Loosestrife… …can alter an entire landscape.

  15. Important Invasives of the Boston Harbor European Green Crab Asian Shore Crab

  16. European Green Crab Accidentally introduced in 1817 Consumes large numbers of juvenile soft-shell clams and oysters Eats $44 million worth of shellfish per year! Impacts of the Invaders

  17. Asian Shore Crab First recorded in Mass. in 1988 Broad diet, disrupts food web Studies show as Asian Shore Crab numbers go up, native crab numbers are decreasing Impacts of the Invaders

  18. Ranges of the Invasive Crabs European Green Crab Asian Shore Crab Boston Boston

  19. What should WE do?These are OUR islands. What can WE do? Become Citizen Scientists!

  20. This kind of science! Not this…

  21. Skills you will need: • Ability to identify a crab’s specie and gender Let’s do it!

  22. Identifying the European Green Crab Five Spines behind each eye Color - can be green, red, yellow, or brown Triangular shaped body

  23. Identifying the Asian Shore Crab Large claws relative to body size Three Spines behind each eye Relatively square body Striped legs

  24. Identifying the native Rock Crab Nine or more Spines behind each eye Color - usually reddish brown Triangular shaped body

  25. Identifying Gender in Crabs This rule works for other species of crab too. Females are more circular Males have the “lighthouse”

  26. Quick Quiz! • List two reasons invasive species can be very successful. • The European Green Crab has __ spines behind each eye. • The Asian Shore Crab has __ spines behind each eye. • The native Rock Crab has ___ spines behind each eye. • Male crabs have a _____________ shape underneath. • Female crabs have a more __________ shape underneath. 5 3 9+ lighthouse circular

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