The first bridge was the Angostura Bridge at Venezuela at Ciudad Bolívar, was completed near Venezuela near Ciudad Guayana. An overhead power line crossing for two 400kV-circuits, had the two spans and three towers. The course of the Orinoco forms a wide ellipsoidal arc, the Guiana Shield. A peculiarity of the Orinoco river system is the Casiquiare canal. 1000 fish species have been recorded about 15 % in the river basin. The far largest orders are Siluriformes and Characiformes. A Venezuelan mining inspector found on a mountain near the Orinoco delta.
Full-scale mining of the ore deposits began by a conglomerate of Venezuelan firms after World War II. The Orinoco River deposits contain also extensive tar sands in the Orinoco oil belt. Maturin forms Guarico and the eastern subbasin, the western subbasin. The local government of Ciudad Guayana has conducted swim race in Caroní and the rivers Orinoco. The city stretches 40 kilometers along the south bank of the Orinoco. The clear Caroní water produces a less muddy zone. WWF is working in Colombia and Venezuela on the ground. The southern part of the ecoregion is wetter with rainfall. Several types of rivers characterize the Orinoco system, this ecoregion. These whitewater rivers carry high sediment loads from the Andes. Large river channels have developed well fringing floodplains at the confluence of the Apure as the internal delta. Six least species of annual killifishes are known from the Venezuelan llanos. Endemic genera include Schultzites, Terranatos and Gymnotichthys. A large number of Orinocan fishes serve for many large river species as migration routes.