Factors affecting the concentration of domoic acid in scallop, Pecten maximus

Domoic acid, a neurotoxin produced by some Pseudo-nitzschia species, can accumulate in shellfish, consumption of which can result in Amnesic Shellfish Poisoning. Since its detection in Irish king scallop, Pecten maximus, regulatory monitoring of toxin levels in product entering the human food chain has been undertaken. Only limited data exist on factors that may influence variability in scallop DA concentration in the field. DA concentration in scallop tissues from a range of sites around Ireland, analysed using HPLC-PDA, exhibited high concentrations in hepatopancreas (max. 3834.4 (ig.g'1), much lower in gonad (max. 61.3 fag.g“1) and even lower concentrations in adductor muscle (max. 31.8 lig.g'1). Toxin concentration in hepatopancreas and scallop size usually exhibited no relationship and there was little support for the hypothesis that shellfish size influenced toxin concentration. DA concentration exhibited site-specific relationships with water depth. Toxin concentration in suspended scallops compared to seabed scallops exhibited a statistically significant difference on only one sampling occasion. Attempts to correlate the occurrence of DA in bivalves with the abundance of cells of Pseudo-nitzschia species were unsuccessful. Given the extent of field variability in DA concentration, a landings-based approach to toxin management rather than an area-based approach would reduce the risks of poisoning.