The metamorphosis of Solea senegalensis was studied in larvae reared at 20 C and fed four different feeding regimes. A, Artemia (4 nauplii ml 1 ); B, Artemia (2 nauplii ml 1 ); C, mixed diet (2 nauplii ml 1 and 3 mg ml 1 microencapsulated diet); and D, microencapsulated diet (3·7 mg ml 1 ). Rotifers were also supplied in all cases during the first days of feeding. These feeding regimes supported different growth rates during the pre-metamorphosis period (regime A, G=0·376 day 1 ; regime B, G=0·253 day 1 ; regime C, G=0·254 day 1 ; regime D, G=0·162 day 1 ). Larvae started metamorphosis 9 days after hatching (DAH) when fed the regime A, 13 DAH with regime B, 11 DAH with regime C and 15 DAH with regime D. A minimum 5·6-5·9 mm L T was required under all feeding regimes to initiate the metamorphosis. Eye translocation was completed when the larvae reached 8·6-8·7 mm L T (regimes A, B and C), but only 7·3 mm L T with regime D. 4·4-6·2 days were required to complete eye migration under the regimes A, B and C, and 18·3 days under the regime D. This transformation is concomitant with changes in body reserves, and with the pattern of some digestive enzymes. 2001 The Fisheries Society of the British Isles