Research – The monitoring program for algal toxins in shellfish 2021


In general, less poisonous shells were detected during the covid-19 years 2020 and 2021 than in the three previous years. We cannot determine whether this is due to fewer samples or less blooms of toxic algal plankton.

In 2021, a total of 723 shell samples were taken and analyzed for various toxins; 384 samples from the Norwegian Food Safety Authority’s annual monitoring program (including the Mussel Alert) and 339 samples from the producers’ own control samples. 

The number of samples from the industry was somewhat fewer in 2021 because demand for shells was lower due to covid-19 with closed restaurants and hotels.

On the monitoring of algal toxins in shellfish

The Norwegian coast is monitored throughout the year for marine algal toxins in shells in connection with commercial harvesting and trade in addition to the Mussel Alert.

The shell samples are analyzed for both the fat-soluble toxins DSP (OA group), AZA, YTX and PTX and the water-soluble toxins with the neurotoxin PSP (STX group), and for the amnesia toxin ASP (DA group).

What did we investigate? Mostly mussels, but also some scallops, flat oysters, Pacific oysters, cockles, knife clams, O-clams, carpet clams, sand clams, circle clams, king snails and sea urchins
Time range: 2021
What were we looking for? The algae toxins DSP, YTX, PTX and AZA, PSP and ASP.
What did we find? Around 98 per cent of all submitted mussels were below the limit value for DSP (OA group).

For PSP (STX group) around 95 per cent were below the limit value, while around 99 per cent were below the limit value for ASP.

For the toxin groups YTX, PTX and AZA, all samples were below given limit values.

Mussels: Had the most detections of DSP and PSP above the limit value, but ASP was also detected above the limit value

Scallops : PSP and ASP were detected above the limit value

Flat oysters : PSP was detected above the limit value in Western Norway for a period in April

PSP : As in previous years, was mainly detected in the spring and early summer.

DSP : The detections above the limit value were distributed throughout the year from April to October with a peak in September. This is consistent with previous years where DSP mainly performs in late summer and autumn.

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