Not all invaders…

come from outer space…

Boston Harbor

Curley School

Invasive Crabs in Invasive Crabs in the Boston the Boston

HarborHarbor

Invasive crabs are Invasive crabs are “exotic”“exotic”

not this kind of exotic…

Exotic species can be animals, plants, or even

microbes (microscopic!)

Exotic species are Exotic species are not not nativenative to the to the ecosystemecosystem

Meaning we’re not originally

from here

Where are we from?

Cows?Rice?Chickens?Apples?

Imagine life without these things!

So, how do exotics get So, how do exotics get here?here?

We introduced some of We introduced some of them them on purposeon purpose

Fact: Fact:

Over 98% of the U.S. food Over 98% of the U.S. food supply are introduced supply are introduced

plants/animalsplants/animals

Or…Or…We introduce them We introduce them

accidentallyaccidentally

For example, ballast water

is used to stabilize the

ship…

but can transport a huge aquarium of exotic life!

These exotics get dumped into local waters.

Ballast water line

Exotic DisasterExotic Disaster

When is an exoticWhen is an exotic invasiveinvasive??

When it spreads rapidly and When it spreads rapidly and out-competes native speciesout-competes native species

A Kudzu invasion blankets all other life

Invasive Invasive successsuccess::They have HIGH They have HIGH reproductivereproductive rates rates

A single female Asian Shore Crab can produce up to 200,000 eggs per year!

That’s twice the rate of native crabs

They leave They leave behind their behind their predators predators and and competitors.competitors.

They play by They play by a different a different set of rules.set of rules.

Invasive Invasive success:success:

Wild boar in the U.S.

Invasives can be Invasives can be harmful…harmful…

They threaten biodiversity

Fact: ½ of all species that are

“endangered” have been impacted by invasives

Many of these endangered species

become extinct

Natural ecosystems support a biodiversity of species

The arrival of an exotic like Purple Loosestrife…

…can alter an entire landscape.

Important Invasives Important Invasives of the Boston Harbor of the Boston Harbor

European Green Crab

Asian Shore Crab

Impacts of the InvadersImpacts of the Invaders

European Green European Green CrabCrab

Accidentally Accidentally introduced in 1817introduced in 1817

Consumes large Consumes large numbers of juvenile numbers of juvenile soft-shell clams and soft-shell clams and oystersoysters

Eats $44 million Eats $44 million worth of shellfish per worth of shellfish per year!year!

Impacts of the InvadersImpacts of the Invaders

Asian Shore CrabAsian Shore Crab First recorded in First recorded in

Mass. in 1988Mass. in 1988 Broad diet, disrupts Broad diet, disrupts

food webfood web Studies show as Studies show as

Asian Shore Crab Asian Shore Crab numbers go up, numbers go up, native crab native crab numbers are numbers are decreasing decreasing

Ranges of the Invasive Ranges of the Invasive CrabsCrabs

European Green CrabAsian Shore Crab

Boston

Boston

What What cancan WE do? WE do?What What shouldshould WE do? WE do?These are OUR islands.These are OUR islands.

Become Citizen

Scientists!

Not this…Not this…This kind of

science!

Skills you will need:Skills you will need: Ability to identify a crab’s specie Ability to identify a crab’s specie

and gender and gender

Let’s do it!

Identifying the European Identifying the European Green CrabGreen Crab

Five Spines behind each eye

Color - can be green, red, yellow, or brown

Triangular shaped body

Identifying the Identifying the Asian Shore CrabAsian Shore Crab

Large claws relative tobody size

Relatively square body

Striped legs

Three Spines behind each eye

Identifying the native Identifying the native Rock CrabRock Crab

Nine or more Spines behind each eye

Color - usually reddish brown

Triangular shaped body

Identifying Gender in CrabsIdentifying Gender in Crabs

Males have the “lighthouse”

Females are more circular

This rule works for other species of crab too.

Quick Quiz!Quick Quiz!

1.1. List two reasons invasive species can List two reasons invasive species can be very successful.be very successful.

2.2. The European Green Crab has __ spines The European Green Crab has __ spines behind each eye.behind each eye.

3.3. The Asian Shore Crab has __ spines The Asian Shore Crab has __ spines behind each eye.behind each eye.

4.4. The native Rock Crab has ___ spines The native Rock Crab has ___ spines behind each eye.behind each eye.

5.5. Male crabs have a _____________ shape Male crabs have a _____________ shape underneath. underneath.

6.6. Female crabs have a more __________ Female crabs have a more __________ shape underneath.shape underneath.

5

3

9+

lighthouse

circular