A re-appraisal of the potential of the sole, Solea solea (L.), for commercial cultivation

Renewed interest in the farming of sole has been stimulated largely by a desire, if not a need, for the existing marine fish farming industry to diversify. Despite the extensive studies of the 1960s and 1970s, commercially viable cultivation techniques for this valuable species were not realised. This species proved relatively easy to rear through the larval stages but the juvenile stages performed poorly on formulated feeds, displaying low growth rates and an apparently high susceptibility to disease. Consequently, effort was directed to other species which did not present such difficulties. Recent research has demonstrated that the technical problems may not be as intractable as was once thought. This paper reviews the results of these studies, which have focused particularly on the problems of providing adequate nourishment to the larvae and juvenile stages. They have demonstrated (a) the ease with which larvae may be reared to the juvenile stages and a link between larval diet quality and juvenile performance, (b) that the reputedly virulent disease, black patch necrosis, may be associated with nutritional deprivation and that juveniles may be grown successfully without a sand substrate, (c) that juveniles can attain a growth rate of over 3 cm per month on natural prey and (d) that diets may be formulated which support survival rates in excess of 90% during weaning and subsequent growth rates approaching those on natural prey. The implications of this work on the prospects for developing commercially viable culture methods is discussed with reference to other important biological characteristics of the species, such as their response to crowding. It is concluded that there are no insuperable problems to the development of cultivation methods for the sole, but further work is required in certain critical areas before economic feasibility can be demonstrated unequivocally.