Diversity and abundance variation of dominant fish species in the river Magdalena delta, Colombia

The fish community in the Magdalena River Delta, Colombia, was studied to a ssess relationship with habitats and to generate additional information for resource evaluation and management programs. Monthly castnets fish collect ions (1995 - 1996) were made in Cienaga Grande de Santa Marta (CGSM), Compl ejo Pajaral (CP) and Complejo Salamanca Occidental (CSO), all in the Magdal ena River Delta; 36 species are present in CGSM, 24 in CP and 42 in CSO, wi th 11 species common to the three areas. Abundance and catch-per-unit effor t were greater in the rainy season, when food availability was greater. The diversity varied during the study period and was higher in CSO where the e nvironmental conditions were better. The geomorphology and environmental co nditions determine the habitat adaptation of the species in the Delta. The dominant species have adapted their spawning, nursery and feeding functions to a yearly salinity pattern.