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

The Ling scallop, Pecten maximus, is a valuable economic resource in the UK . The industry relies on supplying premium "roe-on" processed scallops to t he continental market. In July 1999, king scallops harboring the amnesic sh ellfish poisoning (ASP) toxin, domoic acid (DA), in gonadal tissue at level s above the regulatory limit (20 mug DA g(-1)) were detected across a wide area of northern and western Scotland. In response, a survey of the souther n extent of the closed harvest areas was initiated to describe variability of ASP toxin levels over varying spatial scales (<5 in to >5 km); determine the anatomical distribution of the toxin, and identify, isolate, and cultu re causative Pseudo-nitzschia species. Toxin analysis was conducted using a liquid chromatography-tandem mass spectroscopy (LC-MS/MS) procedure. The D A content of tissues followed the predictable rank order: all other tissue --> gonad --> adductor. The toxin levels within all other tissue (95% CI = 580-760 mug DA g(-1), n 170) consistently accounted for 99% of the total in dividual toxin burden. DA levels in the gonad (95% CI = 8.2-11.0 mug 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, althoug h levels above the regulatory limit were detected in individual gonad sampl es. Adductor muscle tissue contained the lowest concentrations of DA (95% C l = 0.38-0.82 mug DA g(-1), it = 170), and was typically within two to thre e orders of magnitude below levels in all other tissue. None of the scallop s examined had DA toxicities in adductor muscle tissue exceeding the regula tory limit. Toxin variability among individuals and sites was high (range o f coefficients of variation (CV) in all other tissue = 29%-120% and gonadal = 45%-85%). The results do give an indication of the scale on which microh abitat differences may influence ASP toxicity in P. maximus populations, be cause significant differences were found in all other and gonadal tissue to xin levels between groups of individuals only 25-m apart. In total, seven s pecies of Pseudo-nitzschia were identified from west coast waters. A suspec ted causative species, P. australis, was found to produce high levels of DA , in culture. The high individual variation in toxicities and the occurrenc e of DA in the gonad at levels above the regulatory limit clearly demonstra te the complexity of managing the king scallop fishery during ASP events.