Turbot (Scophthalmus maximus)
Also known as: breet, britt, butt
Morphology & Biology
The turbot is a demersal (bottom-dwelling) fish species that is mainly found near the seabed, and is one of the largest species of flatfish. They mainly live in shallow coastal waters, on sandy, stony or mixed bottoms. Turbots prefer water depths of 20-70m.
The turbot is characterised by their flat diamond-shaped body and is left-eyed, i.e. both eyes are on the left side of their body (top), while they rest with their right side (underside) on the sand. Their underside is white and the top is scaly with boney humps, covered with coloured round patches that vary from white to black. The turbot’s colouration blends seamlessly into their environment, making it difficult for predators to see them. Their eyes are relatively far apart (the distance between them is greater than the diameter of an eye) and their mouth is large with sharp teeth. The average size is between 30-60cm, but turbots can grow as large as one meter. Female turbots grow faster than males. The average weight is between 10-20kg, but can sometimes reach 25kg. The life span is between 10-20 years and in rare cases the turbot can reach 25 years.
In most of the turbot’s distribution area, the spawning season is between April and August. The females release their eggs in the open water, in depths of 10-40m. A turbot can release 10-15 million eggs, depending on her size. After fertilization by the male, the eggs develop into larvae which initially have a typical, symmetrical fish shape. The larvae swim upright and feed on plankton. Once the larvae reach a length of 2.5cm, they migrate to begin living near the bottom of shallow waters. As they grow the larvae undergo a transformation in which the right eye migrates over the back of the fish and on to the left side. Once the young fish reach a length of 8-10cm they then move into deeper water. They become sexually mature fish after five years. Turbot is one of the fastest growing flatfish: only the halibut grows faster.
A turbot’s diet mainly consists of other demersal fish, such as sand-eels and gobies. They also eat free-swimming fish like herring and sprat, and small quantities of crabs and mussels. The turbot has a very efficient hunting strategy. They will spend most of their time lying camouflaged on the seafloor, remaining still until prey comes close enough for a sneak attack.
The turbot lives along European coasts, including in the Baltic Sea, the Skagerrak and North Sea, and in the Mediterranean, and also on the North-African coast. In the Black Sea, another species of turbot is native.
According to the IUCN the turbot is “Near Threatened”. The population is estimated to have declined by 20-30% since the early 1980s. Fortunately, fishing pressure has decreased in recent years.
Fisheries & Aquaculture
The turbot is a highly prized flatfish with a high market price. They are commonly caught as by-catch by fishers attempting to capture other demersal fish. As a demersal species, they are most commonly caught with bottom trawls, which severely disturb and damage benthic life and have a high fuel consumption. In some parts of Europe (e.g. Spain and France) the turbot is farmed in aquaculture.
When turbot are young, they have one side on each side of their body, and swim upright. As they mature, the right eye migrates over to the left side of the body, which becomes the turbot’s “top” side.