The waters of Canada and of many parts of the world are invaded by non-native or exotic species. An exotic species is either intentionally or accidentally transported as well as released by man into a new environment. These species are known to be a severe agent of habitat degradation, being the cause of the loss of biological diversity all over the world.
Aquatic species that are introduced in a new environment are not always successful. Ecologists predict that this entire phenomenon will fail. The resistance of the ecosystem depends on the competition between exotic species and native species for both food and habitat. Exotic species can be introduced in an ecosystem by various methods:
- Unintentional Release
Exotic species are released into a new environment without the intention to create an established population. The release of the aquarium pets into a wild environment is a common aspect. Exotic species released from aquariums are red piranha and convict cichlids. Many cultivated plants that escaped accidentally represent a common mechanism to introduce aquatic plants.
- Shipping Activities
There are exotic species released into a new environment by shipping activities. Ocean going vessels are the source of biological invasion. Biological invasions happen when ships discharge ballast water that was taken from the foreign ports.
Canals are joining adjacent watersheds that allow organisms to cross the natural barriers. Canals have greatly contributed to whitefish decline and the populations of lake trout in the Great Lakes.
- Intentional Release
Many exotic species were intentionally released into environments. Fish stocking is the most common example. Fishes introduced intentionally to the Great Lakes were rainbow trout and Chinook salmon.
Impacts of Exotic Species
All in all, introducing exotic species is a risk. However, there is always a different impact as far as exotic species are concerned:
- Ecological impact – bacteria introduced with exotic species are a threat to native organisms. The habitat might be altered and water quality might be changed because of the invaders. Predation of native species by the exotic species might be a real issue. Exotic species might be reproduced with the native ones, resulting in hybrids and the loss of the native species.
- Economic impact ranges from the cost of chemical control agents to the direct economic loss. The economic impact of the exotic species invading the native ones can be huge, as the native species are continuously decreasing.
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