NEWSLETTER
ST. LAWRENCE VISION 2000
VOLUME 10 – ISSUE 4 – SEPTEMBER 1999
Preceding issues

Recreational shellfish gathering on the North Shore
of the St. Lawrence Estuary

This article presents the conclusions of a study undertaken to document recreational shellfish gathering in the territory of the Area of Prime Concern (Zone d’intervention prioritaire, or ZIP in French) along the North Shore of the Estuary from Tadoussac to Pointe des Monts (village of Trinity Bay).

This research project was run by the North Shore Public Health Branch and included a survey of recreational shellfish gatherers and an estimate of the microbiological and chemical risks associated with shellfish consumption.

In the course of the survey, over two hundred gatherers were contacted in eighteen shellfish gathering areas; on average, each area was visited twice. Of these two hundred respondents, 162 were interviewed verbally for about fifteen minutes each.

Variable gathering and consumption patterns

The gatherers surveyed, mostly men between the ages of 20 and 50, can be divided into two categories on the basis of their gathering and consumption patterns; there are casual and regular gatherers (see Table 1).

Table 1 – Distinctive characteristics of shellfish gatherers

The Softshell Clam is by far the species most widely harvested and eaten by the respondents, followed by the Waved Whelk and the Blue Mussel.

The photograph shows, left, the Common Soft-shell Clam; top and mid centre, the Blue Mussel; bottom centre, the Common Northern Buccinum, or Waved Whelk; top and mid right, the Arctic Wedge Clam, and bottom right, the Periwinkle.

The gatherers interviewed eat an average of fifteen meals a year of 410 g of shellfish meat each (each such meal usually comprising an average of 47 clams). Over a third of the gatherers eat shellfish more than twenty times a year. In general, the quantity of shellfish meat per meal varies from less than 80 g to 2,700 g.

Northern Buccinum

Risks and benefits to the health of consumers

The gatherers interviewed for the survey do not attribute any special benefit to a shellfish diet; they eat the organisms just because they like the taste. Yet there are many benefits associated with eating shellfish. They are excellent sources of iron and vitamin B₁₂ and good sources of phosphorus, zinc and niacin.

Similarly, the respondents do not believe that eating shellfish poses any particular risk to their health, even though they know that gathering is prohibited in some harvesting areas. The reason for the ban is that the molluscs concentrate in their tissues certain pollutants found in the ambient water.

The research team assessed the potential microbiological and chemical health risks of eating the Softshell Clam, the bivalve most widely harvested and eaten along the north shore of the maritime estuary of the St. Lawrence. They wanted to determine whether, at the contamination levels measured in clams in the study area, consumption of this shellfish constitutes a substantial source of exposure to microbiological pathogens and chemical products introduced into the maritime estuary. Using the results of the analysis, health risks were assessed for various consumption patterns.

Laboratory analysis of samples taken from various shellfish areas suggests that consumption of the Softshell Clam does constitute a substantial source of exposure to microbiological pathogens and chemical pollutants.

According to Jacques-François Cartier, one of the participating researchers, chemical contamination especially was detected in measurable concentrations for all nineteen pollutants under study, including PCBs and various heavy metals and organochlorines. At present, however, there is no testing for these substances when the quality of shellfish beds is being assayed. The team therefore recommends that a monitoring system be set up to measure these parameters, as well as toxins and contaminants of bacteriological origin, in areas where shellfish are harvested. This monitoring should be done on a regular basis so that any trends in concentrations of chemical pollutants will stand out.

In spite of the concentrations found, there is no reason to advise regular consumers to change their habits, as long as they follow cooking recommendations and stay away from closed areas. In conclusion, Mr Cartier said that the survey suggested the existence of a subsistence harvest, in addition to the casual and regular categories of gatherers. These consumers must be urged to reduce their consumption, but with due consideration for the trouble they will have in substituting another food source for the shellfish, the harvest being a response to a highly problematic local socio-economic context.

TREMBLAY, Thierry, Jacques-François CARTIER and Fabien GAGNON. 1999. Analyse du risque chimique et microbiologique lié à la consommation de mollusques cueillis de façon artisanale dans la ZIP de Baie-Comeau (Analysis of the chemical and microbiological risks associated with consumption of recreationally harvested shellfish from the Baie Comeau Area of Prime Concern), Public Health Branch, North Shore Regional Health and Social Services Board, 150 pages + appendices

Jacques-François Cartier
Health and Environmental Advisor
North Shore Regional Health and Social Services Board
Telephone: (418) 589-9845
Fax: (418) 589-8574
E-mail: Jacques-Francois_Cartier@ssss.gouv.qc.ca