• Amnesic shellfish poisoning in the king scallop, Pecten maximus, from the west coast of Scotland

      Campbell, D.A.; Kelly, M.S.; Busman, M.; Bolch, C.J.S.; Wiggins, E.; Moeller, P.D.R.; Morton, S.L.; Hess, P.; Shumway, S.E. (National Shellfisheries Association, 2001)
      The king scallop, Pecten maximus, is a valuable economic resource in the UK. The industry relies on supplying premium "roe-on" processed scallops to the continental market. In July 1999, king scallops harboring the amnesic shellfish poisoning (ASP) toxin, domnic acid (DA), in gonadal tissue at levels above the regulatory limit (20 μg DA g-1) were detected across a wide area of northern and western Scotland. In response, a survey of the southern extent of the closed harvest areas was initiated to describe variability of ASP toxin levels over varying spatial scales (<5 m to >5 km); determine the anatomical distribution of the toxin, and identify, isolate, and culture causative Pseudo-nitzschia species. Toxin analysis was conducted using a liquid chromatography-tandem mass spectroscopy (LC-MS/MS) procedure. The DA content of tissues followed the predictable rank order: all other tissue -1 gonad -1 adductor. The toxin levels within all other tissue (95% Cl = 580-760 μg DA g-1, n = 170) consistently accounted for 99% of the total individual toxin burden. DA levels in the gonad (95% CI = 8.2-11.0 μg DA g- 1, n = 170) were an order of magnitude below levels in all other tissue and contributed to less than 0.5% of the total individual toxin burden, although levels above the regulatory limit were detected in individual gonad samples. Adductor muscle tissue contained the lowest concentration of DA (95% Cl = 0.38-0.82 μg DA g- 1, n = 170), and was typically within two to three orders of magnitude below levels in all other tissue. None of the scallops examined had DA toxicities in adductor muscle tissue exceeding the regulatory limit. Toxin variability among individuals and sites was high (range of coefficients of variation (CV) in all other tissue = 29&-l20% and gonadal = 45%-85%). The results do give an indication of the scale on which microhabitat differences may influence ASP toxicity in P. maximus populations, because significant differences were found in all other and gonadal tissue toxin levels between groups of individuals only 25-m apart. In total, seven species of Pseudo-nitzschia were identified from west coast waters. A suspected causative species, P. australis, was found to produce high levels of DA, in culture. The high individual variation in toxicities and the occurrence of DA in the gonad at levels above the regula1ory limit clearly demonstrate the complexity of managing the king scallop fishery during ASP events.
    • Factors affecting the concentration of domoic acid in scallop, Pecten maximus

      Bogan, Y. (2006)
      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 (μg.g-1), much lower in gonad (max. 61.3 μg.g-1) and even lower concentrations in adductor muscle (max. 31.8 μg.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.