GENETIC-VARIATION IN NATURAL STOCKS OF SARDINA-PILCHARDUS (SARDINES) FROM THE WESTERN MEDITERRANEAN SEA

Eleven enzymes coded by 15 loci (ADH, SOD*, SDH*, LDH-1*, LDH-2*, ME- 1, ME-2*, GPI-1*, GPI-2*, IDH*, MDH-1*, MDH-2*, PGM*, AAT* and CK*) w ere studied using electrophoretic methods in order to characterize sto cks of sardines from the western Mediterranean Sea. The results showed differentiated groups distributed throughout the area studied. They d id not form a panmictic population, but they existed as semi-independe nt, although not completely isolated, breeding units with an estimatio n of migration of N(e)m = 3.1 (number of migrants per generation). In the LDH-1 system a north-south dine was detected. We have also detecte d a discontinuity between the Alboran and the rest of the Mediterranea n populations sampled at the enzymatic level. This result confirms the action of the Almeria-Oran front asa barrier that produces discontinu ities as detected in other marine species.