Two populations of the fish Cyprinodon dearborni were compared, one from Laguna de Chacopata and the other from Laguna de los Patos, Cumaná, Venezuela. The morphometric method of the Box Truss was used; the organisms were photographed with a digital camera. In the images 18 measures were made to each organism, with the MOCHA 1.2 program. The tendencies of morphologic variation among populations were analyzed by main components using STATGRAPHICS 2.0 and SHEAR programs. The first four main components in males and females explained 88% of the total variation. The components two, three and four separate the two populations based on the body form of the animals. For the electrophoretic study, 13 enzymatic systems were analyzed in starch gels. The variation and genetic distance were calculated with the program GENES 2.0. Differences were observed in the systems G6PDH, GPI; ES and GLUD, that which can be used as isoenzimatic markers. Genetic diversity of Chaco-pata (H = 0.086, p= 0.079) was higher than in Laguna de los Patos (H= 0.029; p= 0.028), but both are within the average in populations of fish. The two populations presented a Nei distance of 0.058. The genetic and morphologic differentiation suggests an incipient process of separation whose causes could be the ecological conditions of their hábitat, or processes of vicariant speciation.
Keywords: Cyprinodon, morphometry, electrophoresis, isoenzymes