Comparative analysis of the diet, growth and reproduction of the soles, Solea solea and Solea senegalensis, occurring in sympatry along the Portuguese coast

Common sole, Solea solea and Senegalese sole, S. senegalensis, were collected between January 2003 and June 2005 from commercial fishing vessels operating with gill-nets and bottom trawls along the Portuguese coast, to examine diet, age and growth and reproduction. Soles fed mainly on crustaceans, polychaetes and bivalves. Feeding activity was highest in summer, for males and for the largest individuals. Significant differences were found between the proportion of prey items according to season, sex and size-class. Common sole presented a wider dietary breadth compared to Senegalese sole. Dietary overlap between the two species was higher for the winter period and for females. Age of soles was determined from sagittae otoliths readings. The length of fish analysed varied between 187 mm and 462 mm (oldest fish 9 years), for S. solea, and between 199 mm and 472 mm (oldest fish 8 years), for S. senegalensis. The von Bertalanffy growth equation coefficients differed between sexes. For both species, the asymptotic length Lee and growth coefficient k obtained for females were higher compared to those estimated for males. The highest values of the gonadosomatic index were obtained for the winter period, when the highest proportion of individuals at spawning stage was recorded.