Introduced species in fisheries and aquaculture
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Biodiversity Impacts
  Colossoma in aquaculture Introduced Pacu (Colossoma macropomum) is also farmed in SE Asia.

Alien species have been identified as one of the most significant threats to aquatic biodiversity. They may adversely affect ecosystems and their biodiversity through:


  • Basic species interactions such as predation and competition
    In the Philippines and Pacific islands the Mozambique tilapia, which can tolerate brackish water, competes for algae and other resources and has displaced mullet, brackish-water shrimp and milk fish in brackishwater bodies.


  • Genetic impacts, such as hybridization and loss of genetic diversity
    Genetic impacts, such as hybridization and loss of genetic diversity through reduced population size from predation and competition. Hybridization between escaped farmed Atlantic salmon and native brown trout in Scotland has been shown to reduce the reproductive efficiency of these species.


  • Habitat alteration
    Many species of freshwater animals greatly modify aquatic habitats when placed in a new area. Notorious in this regard are crayfish, common carp and grass carp.


  • Disease impacts
    New species may bring new pathogens. The introduction of crayfish from North America to Europe also introduced the crayfish plague to European crayfish species. North American species are resistant carriers that also outcompete native European crayfish as a result of higher reproductive rates. The plague gives the invaders an additional competitive advantage by weakening stocks of native European crayfish.



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