By Ella Davies
Earth News reporter
A male Guillet's goby photographed off the Shetland Islands
Europe's smallest marine fish, the Guillet's goby, has been found in Scottish waters for the first time.
Keen-eyed divers photographed the tiny fish while surveying marine life around the Shetland Islands.
Previously, Guillet's goby has only been recorded in British waters three times and never before in Scotland.
The discovery, published in the journal Marine Biodiversity Records, is the most northerly record of the fish and extends the goby's range by 140 miles.
The Shetland Islands are better known for marine life at the larger end of the scale, attracting dolphin and whale-watching tourists.
However, independent marine biologists Dr Richard Shucksmith and Rachel Hope were documenting the islands' smaller species when they made their unusual discovery.
They photographed Guillet's gobies (Lebetus guilleti) at Lunna Kirk on mainland Shetland's Lunna Ness peninsula during dives this summer.
"It never crossed our minds that we would find such a rare fish or that it would be Europe's smallest marine fish," says Dr Shucksmith.
Females are more cryptic
"When Rachel spotted the goby she knew it was something different so made sure she got some pictures so we could identify it when we got home," he says.
The experienced divers were stumped by their discovery at first and had to seek help to confirm its identification.
"Due to its rarity it was in none of the ID guides so with the help of [fellow scientists] it was eventually identified as this rare fish," says Dr Shucksmith.
Those scientists included Dr Lin Baldock, a goby expert, Dr Frances Dipper and Mr Paul Kay who have authored guides to UK fish species, and Dr Marcelo Kovacic of the Natural History Museum, Rijeka, Croatia who found the Guillet's goby in the Adriatic Sea.
In the British Isles, Guillet's goby had only previously been recorded twice in the English Channel and once near the Isle of Man.
Until its discovery off Shetland, the most northerly record of the fish was made in Kattegat, the area of sea between Sweden and Denmark.
The discovery of the fish in Scotland extends its known range by 140 miles.
The Guillet's goby was first identified as a species in 1971 and reaches a maximum size of just 24mm.
There are relatively few records of the fish, possibly because of its small size and secretive nature.
"Its very small size, cryptic colour and its ability to hide amongst shell fragments makes it very difficult to spot," says Dr Shucksmith.
Records to date have identified coarse gravel seabeds as its main habitat.
Dr Shucksmith and Miss Hope were looking for small juvenile fish when they first noticed a male and female pair of gobies.