Preventative measures: The use of potentially invasive alien species for aquaculture and their accidental release/or escape can have negative impacts on native biodiversity and ecosystems. Hewitt et al, (2006) Alien Species in Aquaculture: Considerations for responsible use aims to first provide decision makers and managers with information on the existing international and regional regulations that address the use of alien species in aquaculture, either directly or indirectly; and three examples of national responses to this issue (Australia, New Zealand and Chile). The publication also provides recommendations for a ‘simple’ set of guidelines and principles for developing countries that can be applied at a regional or domestic level for the responsible management of Alien Species use in aquaculture development. These guidelines focus primarily on marine systems, however may equally be applied to freshwater.
Copp et al, (2005) Risk identification and assessment of non-native freshwater fishes presents a conceptual risk assessment approach for freshwater fish species that addresses the first two elements (hazard identification, hazard assessment) of the UK environmental risk strategy. The paper presents a few worked examples of assessments on species to facilitate discussion. The electronic Decision-support tools- Invasive-species identification tool kits that includes a freshwater and marine fish invasives scoring kit are made available on the Cefas (Centre for Environment, Fisheries & Aquaculture Science) page for free download (subject to Crown Copyright (2007-2008)).
Most management techniques to control undesired fish populations are not effective for control of tilapia. Prevention of escape and care in stocking of Oreochromis aureus can effectively prevent their establishment of wild populations. Totally closed systems should always be used when cultivating blue tilapia, and only in watersheds where tilapia have already penetrated. O. aureus aquaculture should be banned from watersheds and lakes in which they have not become established (McCrary et al. 2007).
Physical: Oreochromis aureus populations of Brunner Island, Pennsylvania were eradicated in 1986, when condenser cooling water was deliberately and temporarily released at lethal, low temperature. One study recommended the temperature be brought to 5°C for 16 hours to effectively eradicate O. aureus (Stauffer et al. 1988; Costa-Pierce, 2001; Nico, 2007).
Biological: The use of predatory fish Morone saxatilis X Morone chrysops and Sciaenops ocellatus has been effectively employed to reduce wild spawning among tilapia hybrids (Oreochromis niloticus X Oreochromis aureus) in aquaculture growout ponds. However, such introductions in the wild would have their own ecological effects. Other known predators and possible controls include: snakehead (Channa striata), tarpon (Megalops cyprinoides), Nile perch (Lates niloticus), Hemichromis fasciatus, and Cichlasoma managuens (Milstein et al. 2000).
A management program in Lake Nicaragua to increase the abundance of potential predators of large tilapias, including Oreochromis aureus such as alligators, Crocodrilus acutus, Crocodrilus gars and Crocodrilus elasmobranchs, all vastly reduced from just a few decades earlier, has been recommended (McCrary et al. 2007).
Integrated management: Promotion and augmentation of fishing pressure on O. aureus in order to reduce the average fish size and thereby free niche space for other fishes is another recommended means of controlling their populations (McCrary et al. 2007).
Location Specific Management Information
Attempts to eradicate Oreochromis aurues have failed (Nico, 2007).
The use of predatory fish Morone saxatilis X Morone chrysops and Sciaenops ocellatus has been effectively employed to reduce wild spawning among tilapia hybrids (Oreochromis niloticus X Oreochromis aureus) in aquaculture growout ponds (Milstein et al. 2000).
Oreochromis aureus populations of Brunner Island were eradicated in 1986, when condenser cooling water was deliberately and temporarily released at lethal, low temperature. One study recommended the temperature be brought to 5°C for 16 hours to effectively eradicate O. aureus (Nico, 2007; Stauffer et al. 1988)
A population of Oreochromis aureus in Trinidad Lake was eradicated (Nico, 2007).
2. Centre for Environment, Fisheries & Aquaculture Science (CEFAS)., 2008. Decision support tools-Identifying potentially invasive non-native marine and freshwater species: fish, invertebrates, amphibians.
Summary: The electronic tool kits made available on the Cefas page for free download are Crown Copyright (2007-2008). As such, these are freeware and may be freely distributed provided this notice is retained. No warranty, expressed or implied, is made and users should satisfy themselves as to the applicability of the results in any given circumstance. Toolkits available include 1) FISK- Freshwater Fish Invasiveness Scoring Kit (English and Spanish language version); 2) MFISK- Marine Fish Invasiveness Scoring Kit; 3) MI-ISK- Marine invertebrate Invasiveness Scoring Kit; 4) FI-ISK- Freshwater Invertebrate Invasiveness Scoring Kit and AmphISK- Amphibian Invasiveness Scoring Kit. These tool kits were developed by Cefas, with new VisualBasic and computational programming by Lorenzo Vilizzi, David Cooper, Andy South and Gordon H. Copp, based on VisualBasic code in the original Weed Risk Assessment (WRA) tool kit of P.C. Pheloung, P.A. Williams & S.R. Halloy (1999).
The decision support tools are available from: http://cefas.defra.gov.uk/our-science/ecosystems-and-biodiversity/non-native-species/decision-support-tools.aspx [Accessed 13 October 2011]
The guidance document is available from http://www.cefas.co.uk/media/118009/fisk_guide_v2.pdf [Accessed 13 January 2009].
5. McCrary., Jeffrey K., Brian R. Murphy, Jay R. Stauffer Jr., Sherman S. Hendrix., 2007. Tilapia (Teleostei: Cichlidae) status in Nicaraguan natural waters. Environ Biol Fish (2007) 78:107–114
Summary: Study concerning tilapia in Nicaragua.
6. McKaye, Kenneth R.; Joseph D. Ryan; Jay R. Stauffer, Jr.; Lorenzo J. Lopez Perez; Gabriel I. Vega; Eric P. van den Berghe., 1995. African Tilapia in Lake Nicaragua. BioScience, Vol. 45, No. 6. (Jun., 1995), pp. 406-411.
Summary: A study on the effects of invasive tilapia on Lake Nicaragua.
7. Mendoza, R.E.; Cudmore, B.; Orr, R.; Balderas, S.C.; Courtenay, W.R.; Osorio, P.K.; Mandrak, N.; Torres, P.A.; Damian, M.A.; Gallardo, C.E.; Sanguines, A.G.; Greene, G.; Lee, D.; Orbe-Mendoza, A.; Martinez, C.R.; and Arana, O.S. 2009. Trinational Risk Assessment Guidelines for Aquatic Alien Invasive Species. Commission for Environmental Cooperation. 393, rue St-Jacques Ouest, Bureau 200, Montréal (Québec), Canada. ISBN 978-2-923358-48-1.
Summary: In 1993, Canada, Mexico and the United States signed the North American Agreement on Environmental Cooperation (NAAEC) as a side agreement to the North American Free Trade Agreement (NAFTA). The NAAEC established the Commission for Environmental Cooperation (CEC) to help the Parties ensure that improved economic efficiency occurred simultaneously with
trinational environmental cooperation. The NAAEC highlighted biodiversity as a key area for trinational cooperation. In 2001,
the CEC adopted a resolution (Council Resolution 01-03), which created the Biodiversity Conservation Working Group (BCWG),
a working group of high-level policy makers from Canada, Mexico and the United States. In 2003, the BCWG produced
the “Strategic Plan for North American Cooperation in the Conservation of Biodiversity.” This strategy identified responding to
threats, such as invasive species, as a priority action area. In 2004, the BCWG, recognizing the importance of prevention in addressing
invasive species, agreed to work together to develop the draft CEC Risk Assessment Guidelines for Aquatic Alien Invasive
Species (hereafter referred to as the Guidelines). These Guidelines will serve as a tool to North American resource managers
who are evaluating whether or not to introduce a non-native species into a new ecosystem. Through this collaborative
process, the BCWG has begun to implement its strategy as well as address an important trade and environment issue. With increased
trade comes an increase in the potential for economic growth as well as biological invasion, by working to minimize the potential adverse
impacts from trade, the CEC Parties are working to maximize the gains from trade while minimizing the environmental costs.
Available from: English version: http://www.cec.org/Storage/62/5516_07-64-CEC%20invasives%20risk%20guidelines-full-report_en.pdf [Accessed 15 June 2010]
French version: http://www.cec.org/Storage/62/5517_07-64-CEC%20invasives%20risk%20guidelines-full-report_fr.pdf [Accessed 15 June 2010]
Spanish version: http://www.cec.org/Storage/62/5518_07-64-CEC%20invasives%20risk%20guidelines-full-report_es.pdf [Accessed 15 June 2010].
8. Milstein, A.; Y. Eran, E. Nitzan, M. Zoran and D. Joseph., 2000. Tilapia wild spawning control through predator fishes: Israeli trial with red-drum and hybrid bass. Aquaculture International 8: 31–40, 2000.
Summary: Experiment using predatory fishes as a control for Oreochromis aureus.
10. Stauffer, J.R, Boltze, S.E, Boltze, J.M, 1988. Cold Shock Susceptibility of Blue Tilapia from the Susquehanna River, Pennsylvania. North American Journal of Fisheries Management: Vol. 8, No. 3 pp. 329–332
Summary: An abstract of a study suggesting cold shock as a means of eradicating Oreochromis aureus.
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