Common sole (Solea solea) is a flatfish in the family Soleidae. It is also known as the Dover sole. The name comes from the Dover fishing port, which landed the most common sole in the 19th century.

Average length: 30–40 cm
Maximum length: 60 cm
Average weight: 320 g
Maximum recorded weight: 3 kg
Average lifespan: 4–8 years (the oldest recorded individual was over 20 years old)

What do they look like and where can they be found?

Common sole are nocturnal fish. They are found on sandy or muddy seabeds at depths of 10–60 m. During the day, they lie buried in the sand.

They have a laterally flattened, oval body and a rounded head with a small, curved mouth. Their eyes are located on the right-hand side of their body. Their upper side is greyish-brown, pale yellowish-brown, or greenish-brown, while the underside is white. They usually have large dark mottling and may also have pale or dark spots or blotches.

Life cycle

Common sole begin life as “normal” fish, with one eye on each side of the body. They metamorphose into flatfish when they reach 12–15 mm in length. During this process, one eye migrates to the right-hand side.

Young fish move to shallow bottom waters and later migrate to deeper areas. Sole become sexually mature when they enter their 3^rd-5^th year. Males are smaller than females.

They spawn from March to April off the coasts of Ireland and southern England, in February in the Mediterranean, and from April to July in the southern North Sea. Spawning takes place in shallow coastal waters at temperatures of 6–12°C.

Ecological importance

Common sole feed on bivalves, bristle worms, crustaceans, and occasionally small fish such as gobies and sand eels. Their foraging behaviour helps turn over sediment, which contributes to maintaining healthy seafloor ecosystems.

They are prey for larger fish, including cod and halibut, as well as seabirds.

Commercial value

Common sole are economically important as a food fish. They are highly regarded for their flavour and are often prepared as fillets.

Common sole is one of the flatfish species recorded in the annual landings in Guernsey. The English Channel is one of the areas with high catch rates of sole. 

References:

1. Muus, B. J. (1974). Collins Guide to the Sea Fishes of Britain and North-Western Europe. HarperCollins Publishers.
2. Louisy, P. (2022). Europe and Mediterranean Marine Fish Identification Guide. Les Editions Ulmer.
3. Desender, M., Santos, A.R. (2023). Common sole (Solea solea) in Lyme bay. Cefas report p.44