How genetics can help save freshwater fishes

Globally, most freshwater habitats are moderately or highly threatened. They are often more vulnerable than terrestrial ecosystems of comparable size because they
are linear, making it difficult for aquatic animals to recolonise regions after fragmentation and local extinctions. Freshwater fishes are of particular concern, for they are highly vulnerable to decline following disturbance. They have the highest extinction rate of all vertebrate groups. The extinction crisis faced by freshwater fishes globally is an Australian reality. In the Murray–Darling Basin more
than half of the 50 or so native fish species are considered threatened, and overall native fish populations have probably diminished by about 90% since European colonisation. Overallocation of water for irrigation, altered flow regimes and
record droughts have caused dramatic water shortages. Other threats include reclamation of wetlands, damage to stream banks and vegetation, increased nutrients, and predation and competition by introduced species such as carp, redfin, trout and mosquitofish. There is a lack of community and
government awareness about the plight of native fishes. Efforts to protect and restore populations have mostly been directed at the few large species valued for fishing. Many of the smaller species need urgent attention.