Mussel supply will return to normal next week after the summer weather caused a build-up of toxins in growing beds and led to one third of Scotland’s mussel beds being closed, producers have said.

Sales of live mussels have been limited since mid-July because of the closure of 59 harvest sites in Scotland.

Closures occur every year due to high toxin levels, but this year there were more than usual because of the summer’s “settled” weather, which was conducive to toxin-causing phytoplankton blooms, said FSA Scotland. Last year, there were 50 closures during the full calendar year.

The closures had inevitably led to problems in the supply chain, with many restaurants and shops having no mussels to sell over the summer, said Walter Speirs, chairman of the Association of Scottish Shellfish Growers. “The situation is now continually improving and it looks like harvesting at normal levels will start again very soon.” Consumer safety was a top priority for both shellfish producers and the FSA and the closures should give consumers confidence that everything possible was being done to ensure that shellfish offered for sale was safe to eat, he added.

FSA Scotland said it had seen “one likely outbreak of diarrhetic shellfish poisoning” this year, associated with mussels from Shetland. The last suspected UK toxin incident took place in 2006.