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Listen to this siteWednesday 15 June 2005
This research project used historical data to determine seasonal and long-term trends in levels of domoic acid in king scallops in offshore harvesting areas in Scotland.
Study Duration : June 2004 to November 2004
Contractor : Integrin Advanced Biosystems
Under EU Directive 91/492/EEC, FSA Scotland required offshore king scallops to be monitored for the algal toxin domoic acid (DA). At the time of this study, EU legislation required offshore scallop fishing grounds (offshore boxes) to be closed by FSAS when levels of DA in whole king scallops exceeded 20 mg/kg. In contrast, the new food hygiene regulations that came into effect in 2006 place a greater burden on end-product testing rather than monitoring. The aim of this project was to allow FSAS to develop a risk based approach to offshore monitoring and also to inform suitable sampling frequencies for industry end product testing.
At the time of the study, the offshore monitoring system was based around sub-division of offshore boxes and there was therefore scope for changing the box size (and or shape) to improve efficiency and reduce monitoring costs. The possibility of targeting sampling to periods when there was a good probability that levels had fallen below the regulatory limits was also investigated to offer a more cost-effective programme.
In this study, historical monitoring data was used to determine trends in DA levels in king scallops harvested in offshore areas, and to conduct a critical risk/benefit analysis of modifying the monitoring regime. This study was conducted in parallel with FSAS-funded project S02019, which employed an alternative risk assessment of the Scottish offshore monitoring programme for DA in king scallops.
This study explored the possibility of modelling of Zones of Significant Equivalence (ZSEs) to the Scottish Scallop harvesting activity. If no significant differences were observed between two areas with regard to the domoic acid content of the scallops within them, then it was considered appropriate to treat them as the same area. ZSEs were defined on a range of parameters including DA levels; geographical location; mean depth and percentage land mass in box.
The available datasets were also analysed to determine both the duration of box closures in the past, the robustness of the data underpinning this and the possibility of applying this data to the ZSE approach to define sampling frequency and sampling area after closure.
This study used data from the FSAS monitoring programme for domoic acid (DA) levels in King scallops from July 1998 -March 2004 to determine seasonal and long-term trends in toxin levels over different spatial scales. The toxicity patterns observed in the monitoring data were then employed to advise FSAS on the duration of box closures in the past, the robustness of the data underpinning these closures, and the possibility of applying historical data to define appropriate sampling frequencies and sampling areas for future monitoring and end-product testing.
The results indicated that mean domoic acid concentrations in scallops from Scotland have shown a year on year increase. It is not clear if this represents a genuine rise in domoic acid production in the environment or is a characteristic of the slow growth and long detoxification times that are peculiar to King Scallops. Nonetheless, areas that were associated with low domoic acid levels at the beginning of monitoring are now showing elevated levels, and there is a tendency for all scallops in Scottish waters to exceed the regulatory level of 20 mg/kg. This suggests that they can be treated as a unified regulatory state with regard to whole animal concentrations and monitoring effort switched to improved definition of long term trends. Conversely, scallop gonad concentrations appear to be fluctuating above and below the regulatory level of 20 mg/kg in all areas.
Mean data suggests that domoic acid production is confined to the months between May and November with a peak in September. Bi-modal production may be occurring in some areas with two high periods of production. However, the study found no evidence that domoic acid production is constant in all areas during the domoic acid season. This made it difficult to predict the areas in which domoic acid will rise each month except at very large scales. Detoxification in gonads does, however, occur relatively quickly out of season and is usually below the regulatory level in January for all areas.
Detoxification rates are approximately 30% per month but there are huge differences between boxes and between different months. Intrabox variation in domoic acid levels makes it impossible to accurately predict what the domoic acid concentration will be in a sample from what it was in the previous sample from the same box.
The contractors recommended that the sampling regime be altered so as to collect better data (i.e. more duplicate samples) from fewer areas and to improve the sampling frequency in these �Monitoring Boxes�. It was also suggested that resources be targeted at supporting industry in developing and improving shucking standards so that consumer protection is achieved through improved HACCP and end product testing.
Project completed - Final report is awaited.
Project completed - Final report is currently being evaluated by the Agency.
Contact
: For any enquiries concerning this research project, please contact the relevant Programme contact or email
science@foodstandards.gsi.gov.uk
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