Since the construction of the Canning Dam, among other drinking water supply dams, water flow into the Canning River has been reduced by up to 96%. A number of freshwater fish species which are endemic to the south-west of Western Australia are found in the Canning River system, however studies of fish and fish habitats in the area have shown that fish numbers are low due to a loss of habitat and a loss of linkage between breeding areas due to low flows, preventing fish migrating upstream and reaching important breeding and nursery grounds. Stagnant water caused by a lack of water flow has provided a suitable habitat for successful breeding of an introduced pest, the mosquitofish.