Freshwaters are one of the ecosystems most heavily affected by human activity. Major impacts on biodiversity include pollution, habitat loss and degradation, draining wetlands, river fragmentation and poor land-management. Biodiversity of fish can and does serve as indicators of ecosystem health. Freshwater biodiversity is threatened and has declined in many areas as a result of these impacts.

Aquatic ecosystems (inland and marine) represent the most biodiverse sources of food consumed by humans. This includes vascular plants and algae, and animals such as crustaceans, molluscs, reptiles, amphibians and finfish.  Freshwater ecosystems cover only about 1 percent of the earth’s surface, but provide habitat for over 40 percent (13 000) of the world’s freshwater fish species. Another 2 000 species of fish can also live in brackishwater.

The neotropical regions contain the highest amounts of fish biodiversity and the tropical and subtropical floodplain rivers and wetlands are the ecoregions with the highest levels of biodiversity. Rice fields are an important source of biodiversity and include over 200 species of fish, insects, crustaceans, molluscs, reptiles, amphibians and plants (in addition to rice) that are used by local communities.

Many freshwater species are important to the aquaculture industry as sources of broodstock for spawning and early life history stages (e.g. eggs, larvae) for ongrowing. Non-native aquatic species can contribute significantly to the production and value in inland fisheries and aquaculture.