A marine float covered with club tunicates. /
Photo by PEI Fisheries, Aquaculture & Environment |
What
are they?
Club
tunicates are so named because they resemble
a wooden club. The word “tunicate” is
derived from their tough outer skin or “tunic.” Their
scientific name is Styela
clava.
Club tunicates are solitary animals
and prefer relatively shallow water in
protected bays and inlets with good water
flow. They attach to artificial substrates
such as boat hulls, marina floats and
other in water structures. They can grow
to nearly 8 inches in length.
Tunicates reproduce throughout most of
the year as long as the water temperature
is above 60 degrees F or 15 degrees C,
they reproduce rapidly, forming dense communities.
Why
are tunicates a problem?
Native to the Northwest
Pacific waters of Japan, Korea, Northern
China and Siberia, these tunicates have no
natural predators in this part of the world.
Club tunicates can grow in extremely high densities--up
to 1500 per square yard-- and crowd out
other marine species such as shellfish.
They out-compete native marine
life for space and food. In other parts
of the United States, they have already
created serious problems in sensitive marine
habitats as well as in locations with aquaculture.
The only time club tunicates can move
on their own is in their larval state.
And, as the waters in Puget Sound warm
up, adult club tunicates will begin reproducing
at prolific rates.
As adults, club tunicates are sedentary
creatures. Once they’ve attached
themselves to a surface, they stay there.
But if they adhere to something that moves,
such as a boat, they can relocate to a
different area and potentially establish
new populations. Boaters can be unwitting
accomplices!
In addition, club tunicates can be hard
on boats and marine farming equipment and
other underwater structures. |
