Biological control, as alternative of confrontation of vector organisms, is becoming more necessary every day due to the development of resistance to insecticides. The objetive of this investigation consisted in identifying the species of copepods and fishes that inhabit in the fluvial ecosystems of Sancti Spíritus province, with emphasis in the species with best bio regulators qualities about larval populations of culicids. The investigation comprised the period 2000-2011. In the case of copepods, they are reported new records of the genus Mesocyclops from Cuba, where the species identified possess good bio regulators qualities; in especial, about the first immature phase or stage of mosquitoes. In relation to fluvial fishes, there were carried out six samplings in 90 fluvial ecosystems of eight municipalities from the province, where 15 species of fishes grouped in 12 geneses and six families were identified. It was demonstrated high bio regulator capacity of the species Gambusia punctata and Gambusia puncticulata, giving evidence of changes in the populations of the provincial current fluvial ictiofauna.