The
Shellfish Farm News
July 2003
Summer
is the time of year when shellfish such as oysters spawn,
by releasing their eggs and sperm into the water. There
are male and female oysters and a small percentage of oysters
that produce both sperm and eggs. Oysters can even change
sex from year to year, with the change occurring in the
wintertime. The stimulus to spawn is triggered by increasing
water temperatures. Spawning in sheltered warm bays can
occur every year, whereas in most areas of the coast the
water does not remain warm enough for a sufficient length
of time to stimulate spawning. Oyster farmers at one time
relied on natural sets of seed from summer spawning events,
but these are unpredictable and therefore too unreliable
for operating a business. For the past 20 years most of
the production on shellfish farms has been as a result of
seed purchased by growers from shellfish hatcheries and
planted on their farms.
The
first records of oyster production in British Columbia date
back to 1884, when small native oysters were harvested from
wild populations. The native species of oyster quickly proved
vulnerable to over-harvesting due to their limited stocks,
found mainly in lagoons or sloughs, which protected this
vulnerable species from extremes in temperature, particularly
freezing. Native oysters also proved difficult to farm due
to their slow growth and small size, reaching only 1-2 inches
after 4-5 years growth. Starting in 1912, Pacific oyster
seed from Japan was first planted in British Columbia. The
Pacific oyster proved hardier, faster growing and larger
than the native oyster and has been the basis of oyster
farming on the west coast of North America for most of the
last century. Pacific oyster seed from Japan was purchased
by oyster farmers in B.C. and Washington State up until
about 1961 and brought over on the decks of freighters contained
inside wooden cases. The seed cases were covered with rice
matting to insulate them, and hosed down with seawater at
frequent intervals to keep the seed from drying out during
the crossing, which could take up to 40 days. Two coast
wide spawnings of Pacific oysters occurred in Georgia Strait
in 1942 and 1958 from these early plantings and naturalized
the Pacific oyster throughout the south coast. Oyster production
in B.C. relied heavily on these natural settlements of seed
through the late-1960’s. The development of shellfish
hatcheries in the 1970’s changed seeding practices
so that by the 1980’s most seed originated from hatchery
sources.
In the
last century oyster production has changed from a fishery,
to a ranching-type of operation, relying on wild seed, to
the modern farming business of today, where hatchery technology
complements hard work and ingenuity in producing high quality
affordable products. In the last 20 years, clam farming
has evolved along the same lines, originating as a fishery
and evolving to a ranching and ultimately a farming operation.
Other crops like mussels and scallops have been developed
on shellfish farms in the last 10 years and in the future
species such as abalone and geoducks will be farmed. Farming
these products reduces fishing pressure on wild stocks,
at the same time providing significant economic opportunities,
along with environmental benefits such as creating habitat
and improving water quality.
Excerpts
on the history of oyster farming from: Quayle, D.B. 1988.
Pacific Oyster Culture in British Columbia. Can. Bull. Fish.
Aquat. Sci. 218: 241 p.
|
