Scientists said the critically-endangered species had previously only been found in rivers and know pearl mussels have been discovered in the Scotland Lochs.
The pancakes form when foam floating on a river or the sea freeze. These frozen chunks are then shaped by being rubbed against one another in eddies of water.
Scottish Water says storage levels at some sites are at 66% amid one of the driest summers in 160 years.
'Unprecedented numbers' of pink salmon were seen in 2017 and the fish have been spotted again this year.
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