Depredación de peces sobre el zooplancton en tres embalses neotropicales con distintos estados tróficos

the importance of zooplankton in the diet of small size specimens of astyanax bimaculatus, moenkhausia pittieri, roeboides sp., caquetaia kraussii and geophagus sp. was evaluated in three venezuelan reservoirs with two trophic levels (oligotrophic: taguaza reservoir, hypertrophic: la mariposa and pao-cachinche reservoirs). the fishes were sampled in two hidrological phases (low and high). a total of 998 specimens were analyzed in 30 sampling periods (104 of a. bimaculatus, 127 of m. pittieri, 205 of roeboides sp., 363 of c. kraussii and 199 of geophagus sp.). the size of captured specimens ranged from 15.2 to 97mm of standard length. results were reported as percent frequency of occurrence and percent of total number. the results showed a variation in predation by fishes, according to species and reservoir environmental characteristics. in some cases there was no relation between the zooplankton abundance in the fish diet and the environment. according to zooplankton consumption, species were classified in three groups: high (m. pittieri in taguaza and roeboides sp. in la mariposa), b) moderate (a. bimaculatus in taguaza and geophagus sp. in pao-cachinche) and low consumption (c. kraussii in pao-cachinche). the results revealed an intense intraguild predation between c. kraussii and chaoborus sp. in the pao-cachinche hypertrophic reservoir, which further decreased regulation on the zooplankton community. in contrast, intraguild predation between m. pittieri or roeboides sp. and chaoborus sp. did not occur, while in geophagus sp. or a. bimaculatus it was of low intensity.