Invasive crab species

Over the last few decades an invasive crab native to Europe has been making its way to the west coast.  Recently that crab species was found for the first time in Washington’s Puget sound. Now University of Washington researchers are trying to find out if more of these destructive invaders are lurking in the northwest inland sea. Our environmental reporting partner Earthfix has the story.

TRANSCRIPT

Over the last few decades, an invasive crab native to Europe has been making its way to the West Coast.

Recently, that crab species was found for the first time in Washington's Puget Sound.

Now University of Washington researchers are trying to find out if more of these destructive invaders are lurking in the Northwest's inland sea.

Our environmental reporting partner EarthFix has the story.

[ Water splashing ]

Emily Grason and Sean McDonald are on a hunt.

They're scouring this salt marsh on San Juan Island in Puget Sound in search of a three-inch menace -- the European green crab.

This was the location where our volunteer crew found a single adult male, and this is the first sighting along Washington's inland shores.

And the trap where they found the green crab was right here.

Grason and McDonald are with the Washington Sea Grant Crab Team.

They've set hundreds of baited traps to try to prevent invasive green crabs from setting up a colony.

It might seem like it's crazy for us to have such an intense trapping effort for just a single crab being found.

One crab, what's the big deal?

But these crabs do tend to show up in numbers, and where there's one, there's often more.

We want to be thorough, but we're hoping to not find them, because when we find them, it could be just the beginning of something really terrible.

Green crabs are considered one of the worst global invaders.

So the team is teaching citizen scientists how to identify green crabs, and asking them to keep a lookout.

The green crab has five spines on both sides of its eyes.

So, if there are not five spines, five very distinct teeth to the outside of each eye, then it's likely a native crab.

From their home shores in Europe, green crabs have spread to South Africa, Brazil, Australia, and both coasts of North America.

They are voracious predators, able to crack open mussels and clams.

On the East Coast, their numbers have been on the rise.

They've wreaked havoc on the ecosystem and devastated Maine's soft-shell clam industry.

If they reach the densities here that they do on the East Coast, it would be disastrous.

In a marsh like this, they would burrow into the banks, they would riddle it with holes.

It would cause it to degrade at a faster rate.

Once green crabs become abundant, like here in coastal Maine, they become near impossible to get rid of.

The only effective tool we have for eliminating green crab is trapping.

We don't want to spray chemicals.

We don't want to use any sort of biological control.

But for the time being, there's hope.

After three days, their traps come up empty.

Now I have a little bit more confidence that there's not tons of crabs hiding in pockets of this marsh.

There's always that voice in the back of your head, 'Well, did you look everywhere?

Did we thoroughly explore this entire marsh?'

And there's really no way to know.

They'll be back in the coming months to search some more.