Download Report: Barnstable Sea Farms, Oct 25th, 2011 Jeanette Wheeler

Report: Barnstable Sea Farms, Oct 25th, 2011
Jeanette Wheeler, WHOI/MIT Joint Program Graduate Student
Fall Semester “Marine Invertebrates of Cape Cod”
Oyster Farming at Barnstable
On October 25th, we visited one of the oyster production sites of Barnstable Sea Farms in Barnstable
Harbour. The charmingly incomplete website can be found here: http://www.barnstableseafarms.net/
Click on “staff” to get some idea of the charmingness. Oyster farming is a productive and lucrative trade
in Barnstable, bringing in over 2.5 million dollars per year to the community. We visited a two acre plot
on the mud flats of Barnstable Harbour, where multiple year classes of oysters are reared during the
spring-fall months. The oysters are eastern oysters (Crassostrea virginica) and are non-spawning
triploids. These are specifically developed to waste no energy on spawning and therefore produce a
faster-growing, higher quality oyster.
In the spring, a first year cohort will be initially kept in a fine
mesh bag with approximately 6000 individuals.
The oysters are moved to larger raised mesh bags as they grow
(the bags are kept raised according to a curious Massachusetts
state law). The bags are covered with seawater as the tide
comes in, and the bags have some amount of biofouling
(primarily barnacles and an unidentified tunicate), though
biofouling is considerably worse closer to the edge of the
channel.
An example of tunicate biofouling.
The oysters must be removed from the water prior to the winter, because low water temperatures
(<28oF) will cause ice crystals to lacerate their organs if they are moved beyond this point. Interestingly,
a first year cohort can be removed from the water and kept in a walk-in cooler (at 38o F) in coolers with
some snow shoveled on top of them, and they will hibernate or suspend development until replaced in
seawater (~50o F) in the spring. This is a property of the first year cohort only.
In the second year, the cohort is placed in an open
topped cage on the mud flat. The second year cohort
oysters reach legal selling size (3 inches across)
usually by September. Despite their relative
unguardedness, predation is uncommon, with human
activity being attributed for most predation in the
population. Barnacles are knocked off the shells by
hand before they are sent to market, as dead
barnacles impart a less than pleasant odor to still-live
oysters.
Other Invertebrates at Barnstable
Annelida:
The most obviously abundant polychaete species on the
mud flats were Diopatra (maybe Diopatra cuprea?)
polychaete worms, identified by their characteristic
debris-covered tubes which protrude from the sediment.
The other commonly found polychaete was a Hydroides
species colonizing the insides of old oyster shells
surrounding the farm.
We also found a sipunculan, a peanut worm, on our
walk back, a lucky find because it was certain to show
up on our final exam and nobody had any chance of
identifying a sipunculan as an annelid otherwise (lack
of segmentation).
Mollusca:
We found three species of Crepidula (fornicata, plana,
and convexa) colonizing various mollusc shells on the
mudflat. On the right is a horseshoe crab molt with
colonizing crepidula species.
We found very abundant mud snail (Ilyanassa
obsoleta) populations on the mud flat, probably the
most commonly seen gastropod.
We also found a moon snail (family Naticidae), as pictured, as well
as softshell clams (Mya arenaria), quahogs (Mercenaria
mercenaria), bay scallops (Argopecten irradians), blue mussels
(Mytilus edulis), jingle shells (Anomia simplex) and a
razor clam shell fragment on a Diopatra tube.
Arthopods:
We found multiple species of crab: rock crab (Cancer
sp.?), a sadly homeless hermit crab (family
Paguridae), green crab (Carcinus maenas), and
carapaces of horseshoe crab (Limulus polyphemus)
and spider crab (Libinia sp.?).