Overview
This conference paper reports official INRH monitoring of cadmium in five bivalve species from Dakhla Bay shellfish production areas over nine years. Filter-feeding oysters and mussels carried more cadmium than burrowing razor clams, cockles and clams. Per-season values are shown only as bar charts; station means appear in the ANOVA tables.
Key numbers
- Station means (n = 18): cupped oyster Boutalha 0.922 and Dunablanca 0.842 mg/kg; mussel Puertitto 0.571 mg/kg fresh weight (Table 2, p. 6).
- Burrowing species means: clam (Boutalha farm) 0.372, cockle 0.359, razor clam 0.294 mg/kg (Table 3, p. 7).
- Highest single value 1.55 mg/kg in oysters, Boutalha, winter 2018; burrowing species 0.1 to 0.67 mg/kg (text, pp. 4 and 6).
Methods (brief)
Bivalves depurated 24 h, soft tissue homogenized, pressure-digested (NM EN 13805) and analyzed for cadmium by ICP-MS (NM EN 15763). Results in mg/kg fresh weight. No detection limit, reference material or recovery is reported.
Evidence Fitness
Long monitoring series with direct clam (Ruditapes decussatus) data, but only cadmium, no QA reporting and most values only in figures. The paper’s statements about thresholds are internally inconsistent (a 1.55 mg/kg maximum described as below a 1 mg/kg threshold). Raw clams are a proxy for clam-chowder; that thin page is not linked.