More than 1000 fish species have been recorded in the river basin and about 15% are endemic. Among the fish in the river are species found in brackish or salt water in the Orinoco estuary, but also many restricted to fresh water. By far the largest orders are Characiformes and Siluriformes, which together account for more than 80% of the fresh water species.Hales, J., and P. Petry: Orinoco Llanos. Orinoco Delta & Coastal Drainages. Retrieved 24 May 2014. Some of the more famous are the black spot piranha and the cardinal tetra. The latter species, which is important in the aquarium industry, is also found in the Rio Negro, revealing the connection between this river and the Orinoco through the Casiquiare canal. Because the Casiquiare includes both blackwater and clear- to whitewater sections, only relatively adaptable species are able to pass through it between the two river systems.
More than 1000 fish species have been recorded in the river basin and about 15% are endemic Among the fish in the river are species found in brackish or salt water in the Orinoco estuary but also many restricted to fresh water By far the largest orders are Characiformes and Siluriformes which together account for more than 80% of the fresh water speciesHales J and P Petry Orinoco Llanos Orinoco Delta & Coastal Drainages Retrieved 24 May 2014 Some of the more famous are the black spot piranha and the cardinal tetra The latter species which is important in the aquarium industry is also found in the Rio Negro revealing the connection between this river and the Orinoco through the Casiquiare canal Because the Casiquiare includes both blackwater and clear- to whitewater sections only relatively adaptable species are able to pass through it between the two river systems