Escaped Fish Destroy Native Ecology

Out of the 3072 reported incidents of fish getting loose into a foreign ecosystem, 60 percent have founded wild populations. These introduced fish have sometimes created dire consequences for local environments.

As of 2004, 1674 cases had been documented of species moving into a foreign country.

Freshwater fish account for most of the established exotics. The largest driver behind the invasive spread of fish is aquaculture.

Escapes from fish farms have resulted in 607 confirmed wild populations. The actual total may be much higher since there is no information on whether another 491 introductions have taken hold.

Thirteen aquaculture species are particularly noted for adversely affecting multiple ecosystems. Among the ten fish species under the highest production globally, four have harmed local aquatic habitat.

Common carp is one of the most extensively farmed and most devastating fish species. Its releases into 121 countries have produced thriving wild stocks in at least 91 nations. Fifteen countries report that naturalized common carp are causing damage to ecosystems.

Another widespread aquaculture species, Nile tilapia, has escaped in 85 countries, established in 49 countries and is reported doing harm in 12 of these. Rainbow trout, although less extensively farmed than tilapia and carp, survives wild in 69 countries out of the 90 where it's been released and causes havoc to the ecology of ten countries. Other farmed fish of particular concern are grass carp and silver carp.

The likelihood that farmed species will continue spreading throughout foreign ecosystems remains high as some countries rely heavily on exotic species for aquaculture. The risks are especially pronounced in the large national industries of Philippines, Brazil and Indonesia. Over 70% of their production comes from non-native fish. Although the United States is another top aquaculture producer, foreign species comprise only 3% of its farmed fish.


Christine Marie V. Casal. 2006. Global Documentation of Fish Introductions: the Growing Crisis and Recommendations for Action. Biological Invasions. 8(1): 3-11.

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