Introductions, risk perception and the precautionary approach

By:

Jean R S Vitule, Carolina A Freire and Daniel Simberloff

Certainly, not all fish introductions have catastrophic consequences, but many do. Knowledge about problems that may arise from biological invasions into aquatic systems is growing rapidly, but invasion biology is still a new science. However, we can expect to understand older impacts and to detect new ones in the near future.  Still, aside from the potential ecological problems (and the many that have already been demonstrated) that occur in the short-term, we may be causing changes that will be perceived only in the long-term (for instance, in evolutionary time), at a global scale (see Rahel 2000). As these consequences are still largely unpredictable, a precautionary approach is the best option. One relevant aspect of this complex issue is that introducing fish species usually rewards a relatively small group of individuals or corporations, while society as a whole ultimately pays the costs.  This fact results in pressure to downplay news about possible ecological impacts. Even more importantly, if the precautionary approach is abandoned and concern about introductions is unpublicized, potentially devastating consequences of indiscriminate introduction of freshwater fishes around the globe, especially in megadiverse tropical underdeveloped countries, will simply happen.  An introduction that goes astray usually cannot simply be called back.  Introduction rates are increasing, and the pressure for introductions by individuals or corporations involved in aquaculture for food or ornamental species is very powerful, rapidly outstripping any attempt to understand potential or real impacts.

Introduction of species in general is one of the greatest global threats to the conservation of biological diversity and is generating one of the main forms of global change: biotic homogenization (see Simberloff 2003; 2004; 2005; 2006a; b; 2007; Rahel 2000; Rahel & Olden 2008). For aquatic species, perception of the problem is often delayed, limiting the opportunity for control or eradication; aquatic introductions are usually irreversible, particularly in regions with many endemic species. Fish in particular can easily become serious threats due to their mobility. We do not deny the benefits of some non-native species introductions. Such benefits can accrue quickly, but they are generally restricted, as in control of aquatic weeds and improvement of fish production and/or sport fisheries (Pullin et al. 1997; Bartley & Casal 1998; Vitule 2006; Alves et al. 2007). After these immediate rewards, costs begin to appear. These include changes in natural competition and predation rates, changes in the behavior of native species (fish and other species), limnological perturbations, introduction of diseases and parasites, hybridization with native species, changes in natural assemblages with consequences for fisheries and local economy, and finally local or global native species extinction (and there are many real cases, vide e.g. Pullin et al., 1997; Bartley and Casal, 1998; Pompeu & Goldinho, 2001; Pompeu & Alves, 2003; Townsend, 2003; Begon et al., 2006; Vitule, 2006; Alves et al., 2007). A simple literature search yields many other real-world examples of disastrous freshwater fish introductions.

Aquaculture is often a highly profitable activity in underdeveloped countries, but it is usually inadequately planned.  This is the major cause of global fish introductions (Casal 2006). In addition to aquaculture practices, sport fishing, biological control, pet trade and agriculture are among the main reasons for introducing fish. Construction of canals and irrigation channels has frequently connected formerly separate hydrographic basins, leading to species migration among distinct ichthyofaunal provinces that often results in harmful consequences (Cambray 2003; Agostinho et al. 2005, Vitule et al. 2006). It is also essential to understand that a species of fish can be non-native when moved to a new water body even within the same basin or sub-basin (Cambray 2003; Vitule et al. 2006). There are also many problems associated to illegal handling of animals through the web (WWW). This deleterious activity should be controlled or verified the same way pornographic and other illegal sites are controlled. Currently, through a simple internet search anyone can purchase and illegally introduce exotic aquatic organisms, to many places of the world.

Even worse, in tropical underdeveloped countries (in general with many hotspots, see Abell et al. 2008), laws and law enforcement are minuscule in comparison to the size of the problem.  Legal and regulatory control are almost non-existent in nations such as Brazil (see Alves et al. 2007; Vitule et al. 2009). As noted by Alves et al. (2007): “In summary, although laws governing non-native fish species exist, in practice, fish introductions are of little concern. In fact, any citizen can buy cultured fish from any Brazilian river basin or from another country and release them into privately owned water bodies. The owners and managers of many privately operated hatcheries state in magazine advertisements that their fishes can be delivered to anywhere in Brazil.” This is not a local problem, nor is it restricted to Brazil (e.g. Fuller et al. 1999; Welcomme 1988; Rahel 2000).

            If there is scientific uncertainty with respect to the impact of introducing an exotic species into a new habitat, it should not be introduced there until there has been careful consideration of potential costs and benefits. Once established, an introduced species is usually impossible to eradicate. The notion that economic and social development can be considered independently of the maintenance of biological biodiversity is irrational and unacceptable. The United Nations Conference on Environment and Development that occurred in Rio de Janeiro in 1992 advocated the precautionary principle (United Nations Environmental Programme – UNEP, 1992).  Principle 15 reads: “In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation”.  Further, Article 8h of the Convention arising from that conference calls on all parties to “as far as possible and as appropriate…prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species.”

That the number of freshwater fish introductions will increase is almost certain. If something can be very bad, and its occurrence will grow in the future, what can we consider to be a realistic attitude? Simply to ignore the problem? It seems that some authors (e.g. Gozlan, 2008) are trying to downplay widely acknowledged huge problems associated with introducing freshwater fishes. But it is our duty to warn that, if we do so, and if we minimize the real danger of species introductions based on insufficient and unreliable data, we are aiding people or organizations who think only about immediate profit without considering longer-term losses. The losses will be borne by everyone and will be experienced for many generations.

Despite the recent increase in publicity on this subject, and the many problems that have been documented worldwide, in fact the number of introductions is trending upward (e.g. Rahel 2000; Simberloff 2005; 2007; Wilson, 2006; Rahel & Olden 2008). These factors may generate a feeling of pessimism: there is nothing you can do, so why bother, and after all....this is not so bad.  No, definitely, no! This is an unacceptable attitude. We should be aware that, if we do nothing about this situation, we are sure to have problems in the future. Introduced species can be restricted and avoided, and, if they reach a new environment where they can cause harm to local species or cause other undesirable effects, they must be detected quickly and, if possible, eradicated. If this is not possible, they must be studied, controlled, and an attempt must be made to keep them at acceptable levels.

We expect that this site can help clarify issues and promote debates on this subject, in order to protect the world's biodiversity.

If you are interested in reading more on our point of view, see the references cited or Vitule, J.R.S.; Freire C.A. & Simberloff, D. (2009). Introduction of non-native freshwater fish can certainly be bad. Fish and Fisheries, DOI: 10.1111/j.1467-2979.2008.00312.x, (Early View): http://www3.interscience.wiley.com/journal/120125848/issue

Used references:

Abell R, Thieme ML, Revenga C, Bryer M, Kottelat M, Bogutskaya N, Coad B, Mandrak N,

Balderas SC, Bussing W, Stiassny MLJ, Skelton P, Allen GR, Unmack P, Naseka A, Rebecca

NG, Sindorf N, Robertson J, Armijo E, Higgins JV, Heibel TJ, Wikramanayake E, Olson D,

López HL, Reis RE, Lundberg JG, Sabaj Pérez MH, Petry P (2008) Freshwater ecoregions of

the World: a new map of biogeographic units for freshwater biodiversity conservation.

BioScience 58(5):403-414. doi: 10.1641/B580507

Agostinho, A.A.; Thomaz, M.S. and Gomes, C.L. 2005. Conservation of the biodiversity of Brazil’s inland waters. Conservation Biology, 19:646-652.

Alves, C.B.M.; Vieira, F.; Magalhães, A.L.B. and Brito, M.F.G. 2007. Impacts of nonnative fish species in Minas Gerais, Brazil: present situation and prospects. In: T. M. Bert (ed.), Ecological and Genetic Implications of Aquaculture Activities. (eds T.M. Bert). Springer Verlag, Berlin, pp. 291-314.

Bartley D. 2007. An ecosystems approach to risk assessment of alien species and genotypes in aquaculture. In: Ecological and Genetic Implications of Aquaculture Activities. (eds T.M. Bert). Springer Verlag, Berlin, pp. 35-52.

Bartley, D., and Casal C.V.. 1998. Impacts of introductions on the conservation and sustainable use of aquatic biodiversity. FAO Aquaculture Newsletter 20: 15–19.

Begon M, Harper J.L. and Townsend C.R. 2006. Ecology: individual, populations and communities. Blackwell, Oxford, 759 p.

Fuller P.L., Nico L.G. and Williams, J.D. 1999. Nonindigenous fishes introduced into inland waters of the United States. American Fisheries Society, Bethesda, 613 p.

Cambray, J.A. 2003. The need for research and monitoring on the impacts of translocated sharptooth catfish, Clarias gariepinus, in South Africa. African Journal of Aquatic Science, 28: 191-195.

García-Berthou, E. 2007. The characteristics of invasive fishes: what has been learned so far? Journal of Fish Biology 71 (Suppl. D), 33-55.

Gozlan, R.E. 2008. Introduction of non native freshwater fish: is it all bad? Fish and Fisheries 9, 106-115.

Magalhães, A.L.B. and Jacobi, C.M. 2008. Ornamental exotic fish introduced into Atlantic Forest water bodies, Brazil. Neotropical Biology and Conservation, 2:73-77.

Pompeu, P.S., and C.B.M. Alves. 2003. Local fish extinction in a small tropical lake in Brazil. Neotropical Ichthyology 1(2): 133–135.

Pompeu, P.S., and A.L. Godinho. 2001. Mudanc¸a na dieta da traira Hoplias malabaricus (Bloch) (Erythrinidae, Characiformes) em lagoas da bacia do rio Doce devido a` introducão de peixes piscívoros. Revista Brasileira de Zoologia 18(4): 1219–1225.

Pullin, R.S.V., M.L. Palomares, C.V. Casal, M.M. Dey, and D. Pauly. 1997. Environmental impacts of tilapias. International Council for Living Aquatic Resource Management Contribution 1350: 554–570.

Simberloff, D. 2004. Community ecology: is it time to move on? American Naturalist 163: 787–799.

Simberloff, D. 2005. The politics of assessing risk for biological invasions: the USA as a case study. Trends in Ecology and Evolution 20: 216-222.

Simberloff, D. 2006a. Invasional meltdown 6 years later: important phenomenon, unfortunate metaphor, or both? Ecology Letters 9: 912–919.

Simberloff, D. 2006b. Book review of Black Carp. Biological Synopsis and Risk Assessment of an Introduced Fish. Biological Invasions 8: 1433-1434.

Simberloff, D. 2007. Given the stakes, our modus operandi in dealing with invasive species should be ‘‘guilty until proven innocent.’’ Conservation Magazine 8: 18–19.

Vitule, J.R.S.; Umbria, S.C. and Aranha, J. M. R. 2006b. Introdução de espécies, com ênfase em peixes de ecossistemas continentais. In: E.L.A. Monteiro-Filho, and Aranha, J.M.R. (eds.). Revisões em Zoologia - I: Volume Comemorativo dos 30 Anos do Curso de Pós-Graduação em Zoologia da Universidade Federal do Paraná. Secretaria do Meio Ambiente do Estado do Paraná, Curitiba, 217- 229 p.

United Nations Environmental Programme (UNEP) (1992). Rio declaration on environment and development. Made at the United Nations Conference on Environment and Development, Rio de Janeiro, Brazil. Available at: http://www.unep.org/Documents/Default.asp?DocumentID=78andArticleID=1163.

United States Geological Survey (2000) Zebra mussels Cause Economic and Ecological Problems in the Great Lakes. GLSC Fact Sheet 2000-6. Great Lakes Science Center, Michigan.

Rahel, J. F. 2000. Homogenization of fish faunas across the United States. Science, 288:854-856.

Rahel, F.J. and Olden, J.D. 2008. Assessing the effects of climate change on aquatic invasive species. Conservation Biology 22, 521-533.

Ricciardi, A. 2003. Predicting the impacts of an introduced species from its invasion history: an empirical approach applied to zebra mussel invasions. Freshwater Biology 48, 972–981.

Townsend C.R. 2003. Individual, Population, Community, and Ecosystem Consequences of a Fish Invader in New Zealand Streams. Conservation Biology, 6: 273-282.

Welcomme, R.L. 1988. International introductions of inland aquatic species. FAO - Fisheries Technical Papers n 294, Rome, 318 p.

Wilson, E.O. 2006. The Creation: An Appeal to Save Life on Earth. W. W. Norton and Company, Inc.