Ecological Impacts of Nonnative Freshwater Fishes
TL;DR: The present study provides an illustrative conspectus of the most recent literature reporting ecological impacts of non-native freshwater fishes from a wide range of species and geographic locations and concludes with a prospectus of needed areas of scientific inquiry.
Abstract: There is a long history of introduction of non-native fishes in fresh waters and the introduction rate has accelerated greatly over time. Although not all introduced fishes have appreciable effects on their new ecosystems, many exert significant ecological, evolutionary, and economic impacts. For researchers, managers, and policy makers interested in conserving freshwater diversity, understanding the magnitude and array of potential impacts of non-native fish species is of utmost importance. The present study provides an illustrative conspectus of the most recent literature reporting ecological impacts of non-native freshwater fishes from a wide range of species and geographic locations and concludes with a prospectus of needed areas of scientific inquiry. Both directly and indirectly, invasive fishes affect a wide range of native organisms from zooplankton to mammals across multiple levels of biological organizations ranging from the genome to the ecosystem. Although a great deal of knowledge ha...
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TL;DR: I pose eight questions central to understanding how biological invasions affect ecosystems, assess progress towards answering those questions and suggest ways in which progress might be made.
Abstract: I pose eight questions central to understanding how biological invasions affect ecosystems, assess progress towards answering those questions and suggest ways in which progress might be made. The questions concern the frequency with which invasions affect ecosystems; the circumstances under which ecosystem change is most likely; the functions that are most often affected by invaders; the relationships between changes to ecosystems, communities, and populations; the long-term responses of ecosystems to invasions; interactions between biological invasions and other anthropogenic activities and the difficulty of managing undesirable impacts of non-native species. Some questions have been answered satisfactorily, others require more data and thought, and others might benefit from being reformulated or abandoned. Actions that might speed progress include careful development of trait-based approaches; strategic collection and publication of new data, including more frequent publication of negative results; replacement of expert opinion with hard data where needed; careful consideration of whether questions really need to be answered, especially in cases where answers are being provided for managers and policy-makers; explicit attention to and testing of the domains of theories; integrating invasions better into an ecosystem context; and remembering that our predictive ability is limited and will remain so for the foreseeable future.
334 citations
Cites background from "Ecological Impacts of Nonnative Fre..."
...Planktivorous fishes such as tilapia, cyprinids, or herrings are commonly introduced to lakes, where they may decrease water clarity by eating the zooplankton that help to control phytoplankton (Cucherousset & Olden 2011)....
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...…functions that are most often affected by invaders; the relationships between changes to ecosystems, communities, and populations; the long-term responses of ecosystems to invasions; interactions between biological invasions and other anthropogenic activities and the difficulty of managing…...
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...Impacts of biological invasions on populations and communities have been much better studied than impacts on ecosystems (e.g. Parker et al. 1999; Ruesink et al. 2005; Lovett et al. 2006; Kenis et al. 2009; Cucherousset & Olden 2011)....
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...…populations or communities, and understand them less well (e.g. Parker et al. 1999; Ruesink et al. 2005; Lovett et al. 2006; Kenis et al. 2009; Cucherousset & Olden 2011), Although ecosystem ecologists do study invasions, the field does not appear to put biological invasions on par with…...
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...5, in which invasions affect populations, which alters community structure, which in turn affects ecosystem structure and function (Cucherousset & Olden 2011 presented a similar diagram)....
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TL;DR: This framework demonstrates how comparisons of invader and native functional responses, within and between Type II and IIIfunctional responses, allow testing of the likely population-level outcomes of invasions for affected species, and describes how recent studies support the predictive capacity of this method.
Abstract: Invasion ecology urgently requires predic- tive methodologies that can forecast the ecological impacts of existing, emerging and potential invasive species. We argue that many ecologically damaging invaders are characterised by their more efficient use of resources. Consequently, comparison of the classical 'functional response' (relationship between resource use and availability) between invasive and trophically analogous native species may allow prediction of invader ecological impact. We review the utility of species trait comparisons and the history and context of the use of functional responses in invasion ecology, then present our framework for the use of comparative functional responses. We show that functional response analyses, by describing the resource use of species over a range of resource availabilities, avoids many pitfalls of 'snapshot' assessments of resource use. Our frame- work demonstrates how comparisons of invader and native functional responses, within and between Type II and III functional responses, allow testing of the likely population-level outcomes of invasions for affected species. Furthermore, we describe how recent studies support the predictive capacity of this method; for example, the invasive 'bloody red shrimp' Hemimysis anomala shows higher Type II functional responses than native mysids and this corroborates, and could
227 citations
Cites background from "Ecological Impacts of Nonnative Fre..."
...…et al. 2008; Weis 2010; Morrison and Hay 2011; Chapple et al. 2012) and thus resources, such as native prey species, are vulnerable to potentially severe declines or extinctions (Clavero and Garcia-Berthou 2005; Snyder and Evans 2006; Salo et al. 2007; Cucherousset and Olden 2011; Roy et al. 2012)....
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TL;DR: Convincing stakeholders to comply with management actions aimed at controlling native invaders creates societal challenges and policy makers must prioritize goals from varied and often conflicting human interests.
Abstract: The term “invader” is typically paired with adjectives such as “non-native” and “alien”, yet native species can also cause ecological and economic impacts that rival those of well-known invasive species. By spreading within their historical range, attaining extreme abundances, and exerting severe per-capita effects as a result of predation or competition, native invaders can create an unusual set of challenges for science, management, policy, and society. Identifying when, where, and why species become invaders in their native ranges requires additional scientific inquiry, outside the current focus of invasion biology. Management strategies often mitigate the symptoms rather than address the causes of problematic native species invasions. Convincing stakeholders to comply with management actions aimed at controlling native invaders creates societal challenges and policy makers must prioritize goals from varied and often conflicting human interests. We illustrate these challenges by highlighting native spe...
217 citations
TL;DR: It is demonstrated that current homogenization of the freshwater fish faunas is still low at the world scale but reaches substantial levels in some highly invaded river basins from the Nearctic and Palearctic realms, stressing the need for further understanding of the ecological consequences of homogenized species assemblages.
Abstract: The world is currently undergoing an unprecedented decline in biodiversity, which is mainly attributable to human activities. For instance, nonnative species introduction, combined with the extirpation of native species, affects biodiversity patterns, notably by increasing the similarity among species assemblages. This biodiversity change, called taxonomic homogenization, has rarely been assessed at the world scale. Here, we fill this gap by assessing the current homogenization status of one of the most diverse vertebrate groups (i.e., freshwater fishes) at global and regional scales. We demonstrate that current homogenization of the freshwater fish faunas is still low at the world scale (0.5%) but reaches substantial levels (up to 10%) in some highly invaded river basins from the Nearctic and Palearctic realms. In these realms experiencing high changes, nonnative species introductions rather than native species extirpations drive taxonomic homogenization. Our results suggest that the “Homogocene era” is not yet the case for freshwater fish fauna at the worldwide scale. However, the distressingly high level of homogenization noted for some biogeographical realms stresses the need for further understanding of the ecological consequences of homogenization processes.
184 citations
Cites background from "Ecological Impacts of Nonnative Fre..."
...In addition, the impact of nonnative species introductions on ecosystem functioning has been mostly addressed through species-centered approaches on a limited number of invasive species (29), whereas the ecological consequences of taxonomic homogenization remain largely unknown to date (cf....
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TL;DR: The aim of this paper is to summarise the current knowledge, risk and ecological impacts associated with non-native freshwater fish introductions in South Africa.
Abstract: The introduction and spread of non-native species is one of the least reversible human-induced global changes. In South Africa, non-native fish introductions have occurred over the last two and a half centuries. Resultant invasions have been cited as a primary threat to imperilled South African fishes and other aquatic fauna. Addressing a problem of this magnitude requires an organised approach. The aim of this paper is to summarise the current knowledge, risk and ecological impacts associated with non-native freshwater fish introductions in South Africa. A total of 55 fishes have been introduced into novel environments in South Africa. Of these, 27 were alien and 28 were extralimital
180 citations
Cites background from "Ecological Impacts of Nonnative Fre..."
...2010; Cucherousset and Olden 2011), much still needs to be learnt, particularly in poorly studied geographical regions (Cucherousset and Olden 2011)....
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...Research on the impacts of non-native fishes is therefore important for developing solutions to a difficult conservation problem (Cucherousset and Olden 2011; Richardson and Ricciardi 2013)....
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...129 Analogous to international invasive fish literature (Cucherousset and Olden 2011), taxonomic biases were observed for South African impact studies....
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...Ecologically, impacts span multiple levels of biological organisation ranging from genes to ecosystems and although there is extensive literature on fish invasions and their impacts (Gozlan 2008; Gozlan et al. 2010; Cucherousset and Olden 2011), much still needs to be learnt, particularly in poorly studied geographical regions (Cucherousset and Olden 2011)....
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...Analogous to international invasive fish literature (Cucherousset and Olden 2011), taxonomic biases were observed for South African impact studies....
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References
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TL;DR: This article explores the special features of freshwater habitats and the biodiversity they support that makes them especially vulnerable to human activities and advocates continuing attempts to check species loss but urges adoption of a compromise position of management for biodiversity conservation, ecosystem functioning and resilience, and human livelihoods.
Abstract: Freshwater biodiversity is the over-riding conservation priority during the International Decade for Action - 'Water for Life' - 2005 to 2015. Fresh water makes up only 0.01% of the World's water and approximately 0.8% of the Earth's surface, yet this tiny fraction of global water supports at least 100000 species out of approximately 1.8 million - almost 6% of all described species. Inland waters and freshwater biodiversity constitute a valuable natural resource, in economic, cultural, aesthetic, scientific and educational terms. Their conservation and management are critical to the interests of all humans, nations and governments. Yet this precious heritage is in crisis. Fresh waters are experiencing declines in biodiversity far greater than those in the most affected terrestrial ecosystems, and if trends in human demands for water remain unaltered and species losses continue at current rates, the opportunity to conserve much of the remaining biodiversity in fresh water will vanish before the 'Water for Life' decade ends in 2015. Why is this so, and what is being done about it? This article explores the special features of freshwater habitats and the biodiversity they support that makes them especially vulnerable to human activities. We document threats to global freshwater biodiversity under five headings: overexploitation; water pollution; flow modification; destruction or degradation of habitat; and invasion by exotic species. Their combined and interacting influences have resulted in population declines and range reduction of freshwater biodiversity worldwide. Conservation of biodiversity is complicated by the landscape position of rivers and wetlands as 'receivers' of land-use effluents, and the problems posed by endemism and thus non-substitutability. In addition, in many parts of the world, fresh water is subject to severe competition among multiple human stakeholders. Protection of freshwater biodiversity is perhaps the ultimate conservation challenge because it is influenced by the upstream drainage network, the surrounding land, the riparian zone, and - in the case of migrating aquatic fauna - downstream reaches. Such prerequisites are hardly ever met. Immediate action is needed where opportunities exist to set aside intact lake and river ecosystems within large protected areas. For most of the global land surface, trade-offs between conservation of freshwater biodiversity and human use of ecosystem goods and services are necessary. We advocate continuing attempts to check species loss but, in many situations, urge adoption of a compromise position of management for biodiversity conservation, ecosystem functioning and resilience, and human livelihoods in order to provide a viable long-term basis for freshwater conservation. Recognition of this need will require adoption of a new paradigm for biodiversity protection and freshwater ecosystem management - one that has been appropriately termed 'reconciliation ecology'.
5,857 citations
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...Non-native invasive fish species are increasingly recognized as a significant contributor to extinction threat in fresh waters, one that joins and combines synergistically with habitat loss and fragmentation, hydrologic alteration, climate change, overexploitation, and pollution ( Dudgeon et al. 2006 )....
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TL;DR: Nonindigenous species can bring about a form of extinction of native flora and fauna by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact.
Abstract: ▪ Abstract Nonindigenous species can bring about a form of extinction of native flora and fauna by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially problematic for rare species coming into contact with more abundant ones. Increased use of molecular techniques focuses attention on the extent of this underappreciated problem that is not always apparent from morphological observations alone. Some degree of gene flow is a normal, evolutionarily constructive process, and all constellations of genes and genotypes cannot be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence.
2,190 citations
TL;DR: This paper argues that the total impact of an invader includes three fundamental dimensions: range, abundance, and the per-capita or per-biomass effect of the invader, and recommends previous approaches to measuring impact at different organizational levels, and suggests some new approaches.
Abstract: Although ecologists commonly talk about the impacts of nonindigenous species, little formal attention has been given to defining what we mean by impact, or connecting ecological theory with particular measures of impact. The resulting lack of generalizations regarding invasion impacts is more than an academic problem; we need to be able to distinguish invaders with minor effects from those with large effects in order to prioritize management efforts. This paper focuses on defining, evaluating, and comparing a variety of measures of impact drawn from empirical examples and theoretical reasoning. We begin by arguing that the total impact of an invader includes three fundamental dimensions: range, abundance, and the per-capita or per-biomass effect of the invader. Then we summarize previous approaches to measuring impact at different organizational levels, and suggest some new approaches. Reviewing mathematical models of impact, we argue that theoretical studies using community assembly models could act as a basis for better empirical studies and monitoring programs, as well as provide a clearer understanding of the relationship among different types of impact. We then discuss some of the particular challenges that come from the need to prioritize invasive species in a management or policy context. We end with recommendations about how the field of invasion biology might proceed in order to build a general framework for understanding and predicting impacts. In particular, we advocate studies designed to explore the correlations among different measures: Are the results of complex multivariate methods adequately captured by simple composite metrics such as species richness? How well are impacts on native populations correlated with impacts on ecosystem functions? Are there useful bioindicators for invasion impacts? To what extent does the impact of an invasive species depend on the system in which it is measured? Three approaches would provide new insights in this line of inquiry: (1) studies that measure impacts at multiple scales and multiple levels of organization, (2) studies that synthesize currently available data on different response variables, and (3) models designed to guide empirical work and explore generalities.
1,821 citations
Additional excerpts
...Parker et al. (1999) , we observed a significant difference in the number of studies quantifying impacts at different levels of biological organization ( Figure 1A , chi-square test, χ 2 = 153....
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TL;DR: This work explores the nature of these recent biotic exchanges and their consequences on evolutionary processes, and shows how flexibility in behavior, and mutualistic interactions, can aid in the success of invaders in their new environment.
Abstract: Since the Age of Exploration began, there has been a drastic breaching of biogeographic barriers that previously had isolated the continental biotas for millions of years. We explore the nature of these recent biotic exchanges and their consequences on evolutionary processes. The direct evidence of evolutionary consequences of the biotic rearrangements is of variable quality, but the results of trajectories are becoming clear as the number of studies increases. There are examples of invasive species altering the evolutionary pathway of native species by competitive exclusion, niche displacement, hybridization, introgression, predation, and ultimately extinction. Invaders themselves evolve in response to their interactions with natives, as well as in response to the new abiotic environment. Flexibility in behavior, and mutualistic interactions, can aid in the success of invaders in their new environment.
1,732 citations
Additional excerpts
...When non-native species are introduced into a new environment, native species face new selection pressures in which they must show rapid adaptation to ensure continued persistence ( Mooney and Cleland 2001 ; Strauss et al....
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TL;DR: This work provides a categorization of hybridization to help guide management decisions and recognizes that nearly every situation involving hybridization is different enough that general rules are not likely to be effective.
Abstract: Rates of hybridization and introgression are increasing dramatically worldwide because of translocations of organisms and habitat modifications by humans. Hybridization has contributed to the extinction of many species through direct and indirect means. However, recent studies have found that natural hybridization has played an important role in the evolution of many plant and animal taxa. Determining whether hybridization is natural or anthropogenic is crucial for conservation, but is often difficult to achieve. Controversy has surrounded the setting of appropriate conservation policies to deal with hybridization and introgression. Any policy that deals with hybrids must be flexible and must recognize that nearly every situation involving hybridization is different enough that general rules are not likely to be effective. We provide a categorization of hybridization to help guide management decisions
1,649 citations
Additional excerpts
...Hybridization between native and non-native species has been reported in many fish families, leading to growing concerns of extinction risk ( Rhymer and Simberloff 1996 ; Allendorf et al....
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