Within the order Pleuronectiformes, or also known as flatfishes, we find the family Soleidae and the genus Solea to which the species Solea solea belongs. It is a sole that inhabits the waters of the eastern Atlantic Ocean from the Faroe Islands to Cape Verde in Senegal. It is also present in the Mediterranean Sea. It is a benthic species that lives associated with coastal sandy or muddy bottoms up to depths of 130 meters. It usually migrates to deeper waters during the winter months, and to shallower waters during the summer.
The body of Solea solea is typical of a sole, that is a oval shaped body, slightly elongated and very compressed laterally. The head is relatively small in size compared to the rest of the body, and adopts a blunt-pointed shape at the most anterior end. The head has thin fleshy appendages on the edge of the head that help to visually break the curvature of the face and go more unnoticed against the background.
The body of Solea solea, like that of all soles and related species, despite appearing to be compressed dorso-ventrally, in reality the body is compressed laterally, with the left side of the body always facing the seabed, and the right side upwards in this species. During the larval stage, initially the specimens are pelagic and with bilateral symmetry, so with one eye on each side of the head. It is during the development of the larvae that they will undergo a metamorphosis process by which one of the eyes migrates from one side of the head to the other, so that both eyes end up on the same side of the head, which in the case of Solea solea is the right side. In adults, both eyes are separated by a narrow interorbital space. The uppermost eye is located at a distance from the dorsal profile more or less equivalent to the diameter of the eye itself. As for the composition of the fins of Solea solea, it has a long dorsal fin formed by between 72 and 95 rays and that has its origin in the head at a height before the eyes, and at the back reaches the caudal peduncle. The anal fin is also long, although slightly less than the dorsal fin. It consists of between 53 and 83 rays and is born at the height of the vertical of the operculum and also reaches the back of the body to the caudal peduncle. The right pectoral fin is well developed, and is formed by 7-10 rays and its rear edge is rounded. In contrast, the pectoral fin on the left side, the side against the substrate, is not so developed and is located on the side of the body just before the beginning of the anal fin.
The dominant color of the body of Solea solea is grayish brown on the right or ocular side with a pattern of irregular spots in the same chromatic tonality but with differences in their darkness/intensity, while the left or blind side is whitish. There is a black spot located at the distal end of the pectoral fin on the ocular side, and the posterior end of the caudal fin is usually darker in color than the anterior part.
Adult Solea solea can reach lengths of up to 70 cm, although the most common size to observe is 45 cm in total length. The diet of this species consists of various species of small bivalves, worms, crustaceans and small fish.
The reproduction of Solea solea occurs during the first half of the year. The specimens reach reproductive maturity at about 3-5 years of age. When specimens want to reproduce, they usually migrate to more coastal and shallower waters. Once the eggs are fertilized, they will hatch after approximately 5 days. After a month, the larvae become juveniles, which then undergo the process of metamorphosis until they acquire the characteristics of adult specimens. The life expectancy of this species is 20-25 years.
It is a species whose catches are very considerable as it is a fish that is highly prized in terms of cuisine.
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