The boat was trawling 27 miles south-south-east of Bressay when it caught the shell, which measures 201mm across and weighed in at just over a kilogramme.
Skipper Mark Anderson was very surprised to find an oyster in his nets and brought it to staff at the NAFC Marine Centre who confirmed its record-breaking potential. The previous record holder was reported in Cornwall in 2009 and measured 178mm across and weighed around 1.3kg.
Dr Beth Leslie from the NAFC Marine Centre said: “Native oysters are relatively rare in Shetland waters and for one to be caught in a trawl is very unusual. This oyster was also found at around 120m, which is much deeper than would be expected for this species. Although it is not possible to accurately age the shell it is possible that this individual could have been living for decades.”
The largest oyster ever recorded was in Chesapeake Bay in the USA and was over 300mm across.