Fall 2000/Winter 2001 Table
Waiting Game: Judging the Success of Bay Scallop Restoration on
by Tracey Crago, WHOI Sea Grant
If only time
will tell, the 2001 bay scallop harvest in select Cape Cod locations
will have a message for Dale Leavitt and Diane Murphy. But it isnt
words they are hoping for come October, its bay scallops.
Lots of them.
fisheries and aquaculture specialist for WHOI Sea Grant and Cape
Cod Cooperative Extension (CCCE), and Murphy, CCCE marine program
associate, have spearheaded a bay scallop restoration program on
Cape Cod that is modeled after similar programs in Maryland, Florida,
and New York.
designed strictly as a fishery restoration project, is funded mostly
by Barnstable County with additional support from WHOI Sea Grant
and AmeriCorps. Similar to an aquaculture operation, minus the final
controlled grow-out and harvesting steps, the program uses spawning
scallops are being removed from spat bags to be placed in floating
cages fro the grow-out phase. Photo: R.Karney/M.V. Shellfish
starts with bay scallop juveniles, called "seed," derived from local
broodstock and produced by commercial hatcheries (in this case,
ARC Corp. in Dennis, MA, and Mook Seafarm in Maine). The seed are
placed in bags and put into bottom cages, where they are kept over
the winter. In the spring, the crop of bay scallops is thinned out
so that densities in the spawning cages are less than that of the
over-wintering cages. This allows for the faster growth that occurs
in warmer waters with greater food supply. The spawning cages, which
float, are deployed in early summer. While deployed, the spawning
cages must be maintained, which involves cleaning and removing fouling
organisms, and checking for predation and loss, and later, gathering
samples to check for gonad development. This indicates when the
scallops are about to spawn. In mid-summer, spat collectors are
deployed to monitor the amount of spat released into the waters
surrounding the cages. The spat bagsactually plastic mesh
bagsoffer the larvae a suitable substrate on which to settle.
Now in its
second winter, the program applied lessons learned in the first
year to narrow the focus from nine original over-wintering sites
to five, in the towns of Barnstable (West Bay), Chatham (Ryders
Cove), Falmouth (West Falmouth Harbor), Orleans (Frostfish Cove),
and Yarmouth (Bass River). Two new sites were added this year: Bourne
(Monument Beach) and Eastham (Town Cove). The two sites that were
dropped had low survival rates, ranging from 16 percent to just
under 50 percent. The cutoff, says Leavitt, was anything over 60
"A lot of people were telling us that getting over-wintering survival
rates of 25 percent would be lucky," recalls Leavitt, "and that
survival would not be high enough to warrant the time and energy
the project would require." There were optimists too, who lobbied
for sites in their towns that they believed would offer survival
rates as high as 90 percentconsistently. And, given results
from the first year, they were right. "Survival was highest in places
where we predicted it would be high," says Leavitt. Of course, with
only one winter behind them, Leavitt and Murphy arent ready
to draw any conclusions. Like most shellfish stocks, harvests can
vary dramatically from season to season.
shellfish constable Conrad Caia missed the "banner year" for bay
scallops in 1992, hes been told that Yarmouth bay scallopers
pulled 4,000 bushels from town waters that year. Caia says that
since 1996, when he arrived on the job, Yarmouths catch has
remained steady at around 1,000-plus bushels, generating roughly
$100 per bushel for harvesters.
As a participant
in the restoration program, Caia faced one of its more difficult
challenges last winter: ice. "We had floating cages in Bass River
last year. Id have to go out and chop the ice around the cages
twice a day." (Once the ice thawed, they converted to bottom cages.)
But he was rewarded with a survival rate of 63 percent and deployed
those scallops in spawning cages in Lewis Bay. Caia released the
adults just a few months ago, in October, and is eagerly awaiting
next years harvest. And hes started work on future years
as well, having deployed seed scallops in cages in Bass River. "Only
this year," he says, "were using bottom cages."
constable Paul Montague, of Falmouth, also participates in the restoration
program. He reasons that, with scallop populations down Cape-wide,
this project will only help to get areas going again that were once
productive. Montague admits to being "very surprised" by the over-wintering
results of the first year, particularly in one of his sites, West
Falmouth Harbor. "I had my doubts," he says. "The whole time [they
were there] I kept looking, saying I dont know
The success was outstanding." Indeed, 79 percent of the scallops
that spent the winter in West Falmouth Harbor survived.
In terms of
over-wintering survival in the first year, and the ability to get
those scallops to spawn, the program has been a success. "A lot
of the objectives have been met," says Murphy. As for tracking success,
"that needs work for future years. Wed like to do some genetic
fingerprinting to follow the animals that were supplying.
Knowing the genetic background of the broodstock is crucial to our
ability to show results," she explains.
A WHOI Sea
Grant supported project led by Alan Kuzirian of the Marine Biological
Laboratory succeeded in developing a genetic marker for bay scallops.
The restoration project is now over-wintering offspring of Kuzirians
genetically identified or fingerprinted scallops (see
Two if by Sea, Vol. 2(3)). In the summer of 2001, the survivors
will be planted at a site yet to be determined, where they can be
monitored. Eventually, Leavitt and Murphy will look for third generation
offspring of Kuzirians fingerprinted scallops in the field.
for genetic proof of the projects success, the anecdotal evidence
has kept spirits high. Program participants are willing to attribute,
at least in part, strong sets of bay scallops to the spawning sanctuaries.
Henry Lind, Eastham Natural Resources officer, told Murphy he hadnt
seen that much natural set in five years.
been a lot of learning this year; it was very labor intensive,"
says Murphy. "Fouling [on cages] was a problem [at some sites] and
it made it difficult to deal with equipment. Were not sure
of the effects on the animals. They grew; their gonads and adductor
muscles are comparable to others, so
Murphys hopes for the success of the restoration project in
large part because of what it will mean for the region. But knowing
that the key to assessing the program lies in the genetic fingerprinting
techniques means more waitingand probably some luck as well.
"Any time Ive
played with scallops it seems likes its an incremental thing,"
says Montague. "[You get] some the first year, more the next, and
until you have a crash and no one knows what happened.
I honestly believe no one knows the secret of scallops."
secret may be one reason why Montague and Caia are committed to
making the program as successful as Mother Nature will allow. "Its
an excellent program," says Caia, "and Im willing to do anything
I can to keep it going."