Europe’s smallest marine fish found off Shetland coast

Extremely rare and only 24mm long

October 2010: Europe's smallest marine fish, Guillet's goby, has been found off the Shetland coast at Lunna, by two local divers. This small fish called Guillet's goby grows to a maximum length of only 24mm and was spotted by Rachel Hope and Richard Shucksmith, while they were shore diving at Lunna, Shetland.

It is extremely rare, and since it was described as a species in 1971 there havebe only a handful of sightings around Europe. Four of these were in England, while other sparse records have been from the Mediterranean, northern Spain and one from the Kattegat. This species have never been recorded in Scotland and this finding extends the known range 140 miles further north.

Little is currently known about the biology of Guillets gobies. They seem to prefer living on rough ground such as shelly sand in shallow coastal waters and due to their small size they can hide between the shell fragments, making them extremely difficult to spot.

Male is like a brightly coloured butterfly

Male and females have different colouration (sexual dimorphism). Although both have mottled buff-coloured bodies, the male has a brightly coloured second dorsal fin with a blue spot and orange stripes, much like a brightly coloured butterfly. Gobies are a family of small mostly bottom living fish and share a similar small and elongated body shape. They all have distinctive thick lips and bulbous eyes set close together near the top of the head.

Pairs of gobies were found in Shetland, with the females appearing to be swollen with eggs. Normally in goby reproduction the male will choose the nest site such as an empty shell, or a crevice where the female will lay the eggs. The male will then guard the eggs until they hatch. These pairs seem to indicate that these Guillets goby is breeding in Shetland.

The Guillets goby's known range now must encompass the whole of the UK. Divers and scientists surveying around the coast should look out for this small and beautiful fish when diving or sampling over rough sediment types such as shelly sand or maerl. As more information is collected about this unusual species a clearer picture can be developed about its biology and distribution. It is possible that the spread of this species further north is a climatic range expansion or it could simply be that due its small size and cryptic colouration it has been overlooked.