A colony of tunicates in Guam (Photo by David Burdick, courtesy of NOAA)
Slimy, hungry invaders are moving through
the waters off the Northwest coast of the US.
They’re called invasive tunicates –
or sea squirts. And they’re the same invasive
species that devastated shellfish farms on Canada’s
east coast. If invasive tunicates aren’t controlled,
you could see a lot of seafood options disappear
from markets and menus. Ann Dornfeld has the story:
Transcript
Slimy, hungry invaders are moving through
the waters off the Northwest coast of the US.
They’re called invasive tunicates –
or sea squirts. And they’re the same invasive
species that devastated shellfish farms on Canada’s
east coast. If invasive tunicates aren’t controlled,
you could see a lot of seafood options disappear
from markets and menus. Ann Dornfeld has the story:
It’s a peaceful spring morning at this suburban marina. But beneath the water’s surface, a hunt is
underway.
(water sounds)
Professional divers – like Jesse Schultz with the Washington Department of Fish and Wildlife – are
combing the docks for invasive tunicates. They don’t have to look far.
“That’s one of the tunicates right there – that’s the guy right there.”
Schultz surfaces holding a jelly-like tube. Sea squirts compete with everything from clams to tube
worms for the plankton they all eat. The sea squirts usually win, because they don’t have native
predators. Three species came here from Asia, probably on boat hulls. Today, divers are cleaning
the hulls of local boats to keep the sea squirts from spreading.
Allen Pleus manages invasive species for the state.
“The whole intent right now is a containment action. We want to prevent any of these boats
from leaving this harbor with the tunicates attached to their bottom, going to another
harbor, and infesting that harbor or marina.”
When invasive tunicates get to a new harbor, they quickly become the dominant species. In the
warm part of the year, they spawn every 24 hours. And along with hogging the food supply, one
species of sea squirts forms a slimy mat that smothers mussels and other shellfish.
Pleus says if tunicates get out of hand, they could make a big impact on the seafood industry.
“It can definitely affect especially shellfishing in this area. Puget Sound, Western Washington is one of
the largest producers of shellfish in the nation. It could also affect other populations of
food fish, including salmon, by taking out a lot of the nutrients that juvenile salmon feed
on.”
Nova Scotia learned that lesson the hard way. Pleus says in Eastern Canada, entire shellfish
farms were recently wiped out by invasive tunicates.
“So the rap sheet is clear. They can grow to exponential sizes, quantities and smother
aquaculture facilities. They can’t even lift up their lines it’s so heavy with these critters on
it.”
To prevent the same thing from happening here, the state workers have to move quickly – and
they have to be thorough.
“Here’s another bag, Justin!” (splashing sound)
Back in the water, diving biologist Jesse Schultz has his hands full with a boat that has apparently
been docked for seven years. Its tabs show that’s the last time it was registered.
“This guy’s getting a free boat cleaning, sort of!”
The state is trying to scrape clean every infested boat in Puget Sound before the summer boating
season. But Schultz says because the docks are still covered with invasive tunicates, they’ll grow
back on this boat if the owner doesn’t keep it clean.
“That’s the biggest thing these guys can do to keep these things from spreading is have
their boats maintained.”
The state is still figuring out the best way to clean the docks. So far biologists have cleaned only
one entirely. When they were done, they’d removed ten tons of critters.
Unfortunately, Allen Pleus says only some of those were tunicates. In order to get rid of the
invasive sea squirts, they have to employ a sort of scorched earth policy.
“That is one of the hardest parts of this is that we have to basically take everything out.”
That means the good with the bad. We sift through a bucket of the creatures scraped from the
dock. Along with plenty of invasive tunicates, there are brightly colored sea cucumbers, scallops,
mussels, rock oysters, feather duster worms and chitons – exactly the kinds of animals the state
is trying to protect. They have to destroy the habitat in order to try to save it.
For The Environment Report, I’m Ann Dornfeld.