The Shellfish Farm News
April 2004
Shellfish
provide safe nutritious food and restore ecological balance
As spring advances and the days get longer
the algae blooms that naturally feed shellfish crops increase
in intensity. Clams, oysters and mussels feed on microscopic
algae called phytoplankton, which grows in response to increasing
daylight and nutrients. British Columbia is well known for
producing plump and succulent shellfish because of the rich
plankton blooms that naturally occur here. Our productive
cold waters are fed by abundant rainfall that washes nutrients
from the mountains and creeksides into the sea. These nutrients
accumulate over the winter and combined with increased daylight
in the springtime produce algae blooms that can turn the
water green, red or brown over many areas of the coast.
Not all types of algae are beneficial however;
occasionally areas of the coast are closed to shellfish
harvesting because of so-called “harmful algae blooms”
or “red-tides” (which are not always red). Shellfish
farmers and scientists, in compliance with government food-safety
programs, regularly test shellfish growing areas to ensure
they are free from harmful algae blooms. If a harmful bloom
occurs the affected area is closed to harvesting until it
has passed - taking anywhere from a few days to a few weeks.
Fortunately, few areas of the coast are affected at the
same time, thereby allowing a year-round supply of shellfish
to customers. The shellfish themselves are not harmed by
the bloom and are tested prior to the resumption of commercial
harvesting. In addition, regular sampling is conducted for
harmful bacteria to ensure that shellfish is only harvested
from areas that meet strict government standards. Did you
know that the water quality standard for shellfish harvesting
is 14 times more stringent than the standard for safe swimming?
By feeding upon algae shellfish have a positive
impact on the environment. Excess nutrients from upland
run-off can cause algae blooms to occur at levels that are
detrimental to other types of organisms from sea grasses
to fish. By filtering this excess algae shellfish help increase
water clarity which in turn promotes the growth of seagrasses,
which are an important fish-spawning habitat. Shellfish
also absorb carbon dioxide from the ocean in making their
shells, which are similar to limestone in structure. The
shells function as a carbon “sink”, storing
carbon dioxide and contributing to the reduction of this
important greenhouse gas. In many ways shellfish farming
contributes to the restoration of an ecological balance
upset by other human activities, while creating safe and
nutritious food.
Dave
Mitchell is a Registered Professional Biologist and General
Manager of Fanny Bay Oysters Ltd.
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