The
Shellfish Farm News
March 2005
SHELLFISH
FARMING AND WILDLIFE
Baynes
Sound is located off the east coast of Vancouver Island
and has been an important oyster growing region for over
70 years. In the past 20 years manila clam farming has developed
into another important crop.
Oyster
farmers have observed for decades that planting a crop of
oysters on the beach increases the number of small crabs
and fish that thrive within the oyster crop. Scientific
studies of oyster farming conclude that the oysters are
responsible for this increase in diversity because of the
shelter they provide, allowing more organisms to grow and
reproduce. For example, an increase in the number of small
crabs and fish such as blenny’s provide increased
food for shorebirds.
Shellfish
farmers grow clams by planting clam seed and protecting
their crops with bird netting, the same material that upland
berry farmers use to protect crops of raspberries and strawberries.
The main predator of farmed clams are scoter ducks. Scoters
overwinter in Baynes Sound on the east coast of Vancouver
Island, from October through May, flying north to breed
in the summertime on the arctic tundra.
Recent
studies on the interactions between diving scoter ducks
and manila clam farming are finding a similar beneficial
association between the two. Although clam farmers use netting
to protect their crops from scoter ducks, the ducks are
thriving and increasing in numbers. During the past twenty
years of the development of clam farming in Baynes Sound
the population of scoter ducks has more than doubled, from
2000-3000 overwintering in the early 1980’s to 6,000-8,000
today. Is this a coincidence?
Research
by the Canadian Wildlife Service and Simon Fraser University
have found that scoter ducks are feeding heavily on Manila
clams in Baynes Sound, as well as the more recently introduced
Savoury clam. The clam farms in Baynes Sound are annually
reseeding scoter foraging areas. Clam farmers seed their
farms with juvenile clams in the summer at a size of 5 to
15mm. The clams will spawn at least two or three times before
they are harvested at 3 years of age. As a result, every
year billions of clam larvae are released from clam farms
and drift with the tide to settle on duck foraging areas.
The clam farms therefore are providing a service similar
to the oyster crops, they are increasing the overall amount
of feed available for birds and other wildlife.
Dave
Mitchell is a Registered Professional Biologist and General
Manager of Fanny Bay Oysters Ltd.
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