Prediction of on-site depuration of paralytic shellfish poisoning toxins accumulated in the scallop Patinopecten yessoensis of Ofunato Bay, Japan

In this paper, we present a decay equation for paralytic shellfish poisoning (PSP) toxins using long-term field data spanning more than 10 years in order to predict the detoxification period for the scallop Patinopecten yessoensis in Ofunato Bay, Japan. From the data, we obtained the date of maximum toxicity in the digestive gland (DG) of the scallop and then the date of detoxification. Next, we performed linear regression analysis between log(e)-toxicities and days after the maximum toxicity level for each study year. Toxicity declined at a rate of 1.5 %/day, and a period of 3-9 months was required for the scallop to achieve a toxicity level of 20 mouse units (MU)/g DG tissue, which is a critical level for determining monitoring frequency and area of scallop toxicity. We then estimated the number of days needed to reach 20 MU/g DG tissue (t (20)) using the equations obtained by the above-mentioned analysis, and we performed another linear regression analysis between the log(e) (maximum toxicity) and t (20) for each year. The difference between the actual and predicted detoxification time ranged from -16 to 18 days. We conclude that these equations can be used to predict the depuration of PSP toxins from scallops in Ofunato Bay.