An investigation into the deaths of more than one hundred pearl mussels is taking place by police in Sutherland.
The margaritiferidaes were removed from the River Oykel over the course of the last two months.
They were discovered on the upper reaches of the river near Lubcroy on Thursday, July 4.
Wildlife crime officer Dominic Corcoran said: “Freshwater pearl mussels play a crucial part in sustaining a healthy and natural ecosystem in our rivers
“Anyone disturbing, killing or possessing them is committing a criminal offence and incidents like this are extremely disappointing to everyone who works to conserve this protected species.
“We appreciate that this is a fairly wide timescale but I would urge anyone who believes they may have seen suspicious activity around the River Oykel in recent months to let us know.
“Whoever is responsible for removing them would have needed to spend some considerable time to remove this number of mussels so please think back and let us know if you believe you can assist.”
Freshwater Pearl Mussels are protected under the Wildlife & Countryside Act and it is illegal to disturb, remove, kill or possess them.