Red Tide, PSP and Safe Shellfish Harvesting
Printer-Friendly PDF Version
Bivalve shellfish are an excellent source of protein, are high in essential minerals,
and low in calories, fat and cholesterol. Bivalve shellfish have a hinged two-part shell.
They include oysters, clams, scallops, mussels and cockles.
Bivalve shellfish are highly sensitive to the quality of their marine environment. They
feed on microscopic plants that can sometimes produce marine biotoxins, which can build up
in their tissues. Eating shellfish with high levels of these biotoxins can lead to serious
and potentially fatal illness. Paralytic Shellfish Poisoning (PSP), as well as Amnesic
Shellfish Poisoning (ASP) and Diarrhetic Shellfish Poisoning (DSP) are the most common
human illnesses associated with marine biotoxins in Canada. Bacteria, viruses, metals and
contaminants may also build up in the tissues of bivalve shellfish and cause food safety
concerns for consumers.
The Canadian Food Inspection Agency (CFIA) monitors shellfish harvesting areas to
provide early warning of PSP toxins (and other toxins) in shellfish. Hundreds of sites in
Atlantic Canada, Quebec and British Columbia are regularly tested for PSP toxins. The
Agency analyzes shellfish samples and, when levels are unacceptable, it notifies the
Fisheries and Oceans Canada (DFO) which takes immediate action to close the affected area
to shellfish harvesting. When areas are closed, signs are posted, media are notified, and
DFO fishery officers patrol the areas to prevent the harvesting of shellfish.
What is Red Tide?
Under specific marine environmental conditions, certain species of microscopic algae
can multiply rapidly causing a "bloom" in population. This phenomenon is
commonly referred to as a red tide because, at times, seawater can become discoloured from
the dense accumulation of algae. Algal blooms are most common in the spring and summer
months when sunlight, temperature and precipitation favour algal growth. However, algal
blooms can occur at other times of the year as well. Red tide events can include
biotoxin-producing algae that can contaminate bivalve shellfish in the area. It is also
important to note that many toxin-producing algal blooms do not produce color and cannot
be readily seen from shore.
For more information on Red Tide, visit DFO's
Web site at: www.dfo-mpo.gc.ca.
What is Paralytic Shellfish Poisoning?
Paralytic Shellfish Poisoning (PSP) is an illness caused by marine biotoxins produced
by blooms of microscopic plankton. PSP toxins can accumulate in a number of filter-feeding
bivalve shellfish such as clams, mussels, scallops and oysters, and in the tomalley of
crustaceans such as lobsters.
Symptoms of PSP include tingling and numbness of the lips, tongue, hands and feet, and
difficulty swallowing. In severe situations this can proceed to difficulty walking, muscle
paralysis, respiratory paralysis and death in as quickly as 12 hours.
So how can you protect yourself and your family?
First, be cautious when harvesting bivalve shellfish. It is your responsibility to call
your nearest Fisheries and Oceans Canada (DFO) office (listed in the blue pages of the
local telephone directory) to find out which areas are assigned as open for
bivalve shellfish harvesting. An open area refers to a safe harvest area that
is subject to monitoring and testing, and where harvesting is a legal activity. When an
area is officially closed, it is illegal to harvest bivalve shellfish in that
area for any purpose, unless a special scientific licence is issued.
Watch and listen for updates on the opening and closing of harvesting areas. These are
communicated to the public through local media, notices posted in closed areas, and
information provided by local DFO offices. It's also important that you purchase bivalve
shellfish only from suppliers you trust and those who have harvested from open areas
approved by DFO.
Once you get them home, bivalve shellfish should be refrigerated or frozen until
they're ready to be eaten. Be mindful that cooking bivalve shellfish does not destroy
toxins such as PSP or other contaminants. Properly cooked shellfish can still be toxic.
Anyone who feels ill after eating bivalve shellfish should immediately seek medical
attention. There isn't one particular season that is safer than another; bivalve shellfish
can have high levels of marine toxins during any given month, depending on environmental
conditions. If you're planning on harvesting shellfish during your next vacation, remember
that bivalve shellfish poisoning can also occur in other countries. Tourists should be
cautious when consuming bivalve shellfish abroad.
For more information, visit the CFIA Website at
www.inspection.gc.ca or call 1 800 442-2342/TTY 1 800 465-7735 (8:00 a.m. to 8:00 p.m.
Eastern time, Monday to Friday).
To find out which bivalve shellfish harvesting areas are open, call your nearest DFO
office listed in the blue pages of your local telephone directories.
P0487E-06
|