First Nations harvesters are being reminded of shellfish closures during the upcoming shellfish harvest season. Summer is a common period for toxic forms of algae to increase in ocean water as a result of warming water temperatures. Concentrations of toxins can accumulate in filter-feeding shellfish, such as clams and mussels. When contaminated shellfish are consumed, illness can result.
In 2015, high levels of domoic acid were detected along Vancouver Island and Haida Gwaii. Typically present in California, higher domoic acid levels in BC are being attributed to warming ocean waters. Domoic acid is a naturally occurring toxin produced by certain types of algae, and at high levels, can be harmful or even fatal to humans. It is referred to as amnesic shellfish poisoning (ASP). Some algae found in red-tide can produce toxins, and at high levels may lead to paralytic shellfish poisoning (PSP). The absence of a red algae bloom is not a good indicator of shellfish safety.
Shellfish that have accumulated toxins will not appear to be ill or contaminated. Shellfish that can be affected include: clams, oysters, scallops, mussels, cockles, geoducks, whelks, periwinkles or the innards of lobster and crab.
Symptoms of shellfish poisoning
Symptoms of shellfish poisoning can occur within 30 minutes and up to 24 hours after eating contaminated shellfish. In mild cases, symptoms may include vomiting, diarrhea, abdominal cramps, headache, dizziness, muscle weakness, disorientation, memory loss, loss of coordination, or difficulty swallowing. These symptoms disappear within several days. In serious cases, seizures, unstable blood pressure, paralysis, difficulty breathing, coma or death may occur. There have been no reported illnesses in BC.
At the first sign of such symptoms, contact your Poison Control Centre at 1.800.567.8911 for first aid advice and seek medical attention immediately.
- Cooking does not render the shellfish safe.
- The best way to keep safe is not to harvest shellfish from closure areas.
- Health Authorities are working with the BC Centre for Disease Control, the Canada Food Inspection Agency (CFIA) and Department of Fisheries and Oceans (DFO) in the monitoring of harvest areas to ensure that impacted and shellfish are not commercially distributed into the human food supply.
- Shellfish that are harvested for sale are monitored and tested by the CFIA; shellfish from an approved source are considered safe for consumption in moderate amounts. FNHA is working with agencies to improve monitoring in areas not used for commercial harvesting and which may have greater use by First Nations self-harvesters.