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Exotic fish species in the watershed of Hamilton Harbour Back to the Fishway What are exotic species? Exotic species are those species that did not evolve in the local ecosystem and whose presence can be attributed to the activities of humans. Many of the familiar members of Hamilton Harbour’s fish community are exotic. They were intentionally or accidentally introduced into the watershed. How do exotic species get here? Although many of the exotic fish species in the watershed established in the 1800’s, the rate of introduction of exotic species has increased in the past 30 years. This increase roughly coincides with the opening of the St Lawrence Seaway and points to one of the major routes of entry for exotics – in the ballast water of ships. Other methods of entry include: a) artificial shipping canals (e.g. alewife); b) release of unwanted fish from home aquaria, backyard ponds and water gardens (e.g. goldfish); c) escape of fish from aquaculture facilities; d) use of live bait; e) stocking of exotic species for management, sport or commercial fishing purposes; f) unauthorized transfer of fish or other aquatic organisms from one waterbody to another. Why are they a cause for concern? The establishment and spread of exotic species is considered one of the primary causes of the decline of aquatic biodiversity. Some examples of the impacts of exotic fish species include: 1. altering/disturbing the physical habitat of native species (e.g. common carp); 2. competition with native fish for food and habitat (e.g. round goby); 3. diminishing the health of native species (e.g. round goby were implicated in severe outbreaks of botulism in some fish and fish-eating birds; alewife and smelt are linked to thiamine deficiency in native salmon and trout); 4. impairing the use and enjoyment of the watershed’s fish resources by reducing the viability of sport fisheries (e.g. sea lamprey), fouling beaches (e.g. alewife), diminishing the quality of sport fishing experience (e.g. round goby) In addition to the alarming ecological impacts that exotic species can have, they are also very expensive. American researchers estimate that exotic fish species cost the US economy more than 1 billion dollars annually, even taking into account the positive economic contributions that exotic fish make tot the American sport fishery(1). A similar aggregate cost is not available for Canada. However, we do know the costs of controlling specific exotic fish species. For example, the sea lamprey control program for the Great Lakes costs in excess of US$15 million annually(2) (GLFC 2000). 1 Pimentel, D. et al. 1999. ENVIRONMENTAL AND ECONOMIC COSTS ASSOCIATED WITH NON-INDIGENOUS SPECIES IN THE UNITED STATES. http://www.news.cornell.edu/releases/Jan99/species_costs.html 2 Great Lakes Fishery Commission (GLFC). 1999. SEA LAMPREY ANNUAL REPORT 1999. http://www.glfc.org/sealamp/ANNUAL_REPORT_1999.pdf What exotic fish species are currently present in the watershed? There are currently 14 fish species established in the watershed that are thought to be exotic species.
* There is disagreement concerning the native status of alewife in Lake Ontario. The first record from Lake Ontario was in 1873. It is possible that alewife were introduced into Lake Ontario with the stocking of American shad. Some researchers argue that alewife were only able to invade the lake after the decline of predators such as lake trout and Atlantic salmon in the 1860s. Others believe this species was native to Lake Ontario and spread through the Great Lakes via the Welland Canal (http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=490). **It is unclear whether gizzard shad are native to the Great Lakes or gained access through canals and rivers in New York such as the Mohawk River, Oswego River, Erie and Barge Canals (http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=492). *** The Lake Ontario population may be either native to this lake or migrated downstream, possibly through the Welland Canal. Another possibility is that the species was introduced from the Finger Lakes via canals. (http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=796) Not all exotic species are created equal Although all exotic species that establish in an ecosystem have some degree of impact on native species, some exotic species are considered more detrimental than others. For example, in the Hamilton Harbour watershed, the common carp [hyperlink] is one of the key stressors in the ecosystem and was a primary cause for the continuing decline of habitat quality, particularly in Cootes Paradise. As such, reducing the size of the carp population became a priority for restoration. Other exotic species are maintained in the ecosystem through management of fish stocks. For example, many of the salmon species found in the watershed are actually native to the Pacific coast, but were originally stocked into Hamilton Harbour or Lake Ontario for sport fishing and/or control of alewife populations. What can be done about exotic fish species? Once established, exotic species are extremely difficult to completely eradicate. The fish barrier [hyperlink] at the mouth of Cootes Paradise has been successful at eliminating the majority of carp from the marsh and as a result, has helped reduce the carp population in the harbour. Keeping carp out of areas like Cootes Paradise requires constant vigilance and considerable effort. After a new exotic species has successfully gained a foothold in an ecosystem, one of the challenges facing resource managers is to prevent it from spreading further. Members of the public can aid this by: 1. carefully and thoroughly cleaning their fishing gear (boats, trucks, etc) when they move between locations 2. abiding bait fish regulations 3. reporting sightings of exotics 4. disposing of aquaria/pond fish properly. For further information on exotic species in the Great Lakes, visit these websites: Great Lakes Commission Aquatic Nuisance Species Great Lakes Information Network Invasive Species in the Great Lakes Region Ontario Federation of Anglers and Hunters Invading Species USGS Nonindigenous Aquatic Species Ministry of Natural Resources Back To Top
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Science contacts Ask our science staff a question about the science and conservation program. Science fact sheets Download a fact sheet and learn about our restoration projects. The Fishway Find out how we keep carp out of Cootes Paradise and how you can see native fish up close. Project Paradise Learn about the one of the largest habitat restoration projects in North America. Library Books, archives, nursery and seed trade catalogues, a slide library and much more. Directions Click here to see how easy we are to find. Local weather Find out the local forecast before you head out! |
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