Fish rarely feature on the Nature in Shetland website, but we received a press release the other day which is well worth reading as it describes a n interesting and endearing little fish and shows what there is that can still be discovered about Shetland's fauna.
Europe’s smallest marine fish, Guillet’s goby, has been found off the Shetland coast at Lunna, by two local divers, Rachel Hope and Richard Shucksmith.
This small fish called Guillet’s goby (Lebetus guilleti) only grows up to a maximum length of 24 mm (upper photo of male by Rachel Hope and lower photo of female by Richard Shucksmith). It was spotted by two local divers whilst shore diving at Lunna, Shetland. It is an extremely rare fish and was only described as a species in 1971. There are only a handful of sightings of this species around Europe including 4 in England and other sparse records are from the Mediterranean, northern Spain and one from the Kattegat (previously the most northerly record). This species have never been recorded in Scotland and this finding extends the known range 140 miles further north. 
Due to the importance of this sighting it has been accepted for publication in the peer reviewed Marine Biological Association Journal ‘Marine Biodiversity Records’.
Little is currently known about the Guillet's goby's biology. It seems to prefer living on rough ground such as shelly sand in shallow coastal waters and due to its small size it is able to hide between the shell fragments, making it extremely difficult to spot. Male and females have different colouration (sexual dimorphism), although both have mottled buff coloured bodies. However 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.
When we found this species the males and females were found as pairs together 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 Guillet's goby is breeding in Shetland.
By finding this species in Shetland it means that its 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.
Shetland is famous at migration time for its rare birds and this find shows that it should be famous for its rare marine life too!
