Diet, growth and reproduction of four flatfishes on the Portuguese coast

Four flatfish species were collected between January 2003 and June 2005 from commercial fishing vessels operating with gill nets and bottom trawls along the Portuguese coast in order to examine feeding habits, age and growth and reproduction. Citharus linguatula (Linnaeus, 1758), Lepidorhombus boscii (Risso, 1810) and Microchirus azevia (de Brit Capello, 1867) fed mainly on crustaceans, whereas Platichthys flesus (Linnaeus, 1758) fed mainly on echinoderms and crustaceans. Feeding activity was highest in spring and summer; females and small individuals showed the lowest vacuity index values. For all the species, significant differences were found in the proportion of prey items according to season, sex and size class. M. azevia had the largest diet spectrum. Ages were determined from sagittal otoliths. The von Bertalanffy growth equation coefficients differed between sexes. The asymptotic length L(infinity) of females was higher than that of males, except in C. linguatula. The lowest growth coefficient was obtained for P. flesus (k=0.11 for males and k=0.10 for females) and M. azevia showed the highest growth coefficient estimates (k=0.40 for females and k=0.30 for males). The highest proportion of individuals at spawning stage was recorded in winter for L. boscii, P. flesus and M. azevia, and in autumn for C. linguatula.