Why are toxic shellfish in Lochaber becoming more common?

The short answer is climate change, but the long answer is much more complex. 

These incidents are being caused by toxic algal blooms, a naturally occurring phenomenon which happens when water temperatures rise, causing algae in the water to multiply rapidly. 

Bivalve shellfish like mussels, cockles, oysters or razor fish, eat by pumping seawater through their bodies to filter out and consume phytoplankton. But when these toxic algae are present in the water, they absorb the toxins into their flesh.

While the toxicity is not permanent, the shellfish are dangerous to eat while the toxins are still in their systems. They could cause gastroenteritis and diarrhea, with symptoms lasting from a few days to a week. 

This is exactly why commercial shell fishing is currently halted in Loch, Sunart Moidart and most recently Loch Beag. A similar warning was also in place in Skye’s Loch Eishort this summer, which has now ended, and also in a small patch of Loch Linnhe.

All of these warnings are still in place, and commercial fishing in these lochs has stopped. 

While these warnings happen every year, in 2026 they have been much more common. But why?

Professor Keith Davidson from the Scottish Association for Marine Science (SAMS) says that 2026 has simply been "a bad year".

Professor Davidson was part of a 15 year study into patterns of harmful algae affecting Scottish Aquaculture, which found no year on year increase. 

He explains that while algal blooms are becoming more common due to rising sea temperatures, a direct result of climate change, there is currently no evidence of an upward trend in harmful incidents.

"There are hundreds of thousands species of phytoplankton in our waters, and for shellfish biotoxins only seven or eight are harmful," he said. 

"The vast majority are perfectly benign and actually really important for the carbon cycle."