Fish Invasions in the World's River Systems: When Natural Processes Are Blurred by Human Activities

Laboratoire Evolution and Diversité Biologique, UMR 5174, CNRS-Université Paul Sabatier, Toulouse, France.
PLoS Biology (Impact Factor: 11.77). 03/2008; 6(2):e28. DOI: 10.1371/journal.pbio.0060028
Source: PubMed

ABSTRACT Because species invasions are a principal driver of the human-induced biodiversity crisis, the identification of the major determinants of global invasions is a prerequisite for adopting sound conservation policies. Three major hypotheses, which are not necessarily mutually exclusive, have been proposed to explain the establishment of non-native species: the "human activity" hypothesis, which argues that human activities facilitate the establishment of non-native species by disturbing natural landscapes and by increasing propagule pressure; the "biotic resistance" hypothesis, predicting that species-rich communities will readily impede the establishment of non-native species; and the "biotic acceptance" hypothesis, predicting that environmentally suitable habitats for native species are also suitable for non-native species. We tested these hypotheses and report here a global map of fish invasions (i.e., the number of non-native fish species established per river basin) using an original worldwide dataset of freshwater fish occurrences, environmental variables, and human activity indicators for 1,055 river basins covering more than 80% of Earth's surface. First, we identified six major invasion hotspots where non-native species represent more than a quarter of the total number of species. According to the World Conservation Union, these areas are also characterised by the highest proportion of threatened fish species. Second, we show that the human activity indicators account for most of the global variation in non-native species richness, which is highly consistent with the "human activity" hypothesis. In contrast, our results do not provide support for either the "biotic acceptance" or the "biotic resistance" hypothesis. We show that the biogeography of fish invasions matches the geography of human impact at the global scale, which means that natural processes are blurred by human activities in driving fish invasions in the world's river systems. In view of our findings, we fear massive invasions in developing countries with a growing economy as already experienced in developed countries. Anticipating such potential biodiversity threats should therefore be a priority.

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Article: Fish Invasions in the World's River Systems: When Natural Processes Are Blurred by Human Activities

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    • "La introducción de peces en aguas continentales es de larga data y se ha realizado principalmente con fines de acuicultura, acuariofilia y pesca recreativa (Welcomme 1988). Sudamérica es uno de los seis " hotspots " globales de invasión de peces de agua dulce (Leprieur et al. 2008) y muestra una significativa homogenización de su fauna de peces (Villéger et al. 2011). Los ríos y lagos de Chile no han sido la excepción, estando la gran mayoría de estos sistemas continentales invadidos por una o más especies de peces exóticos. "
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    DESCRIPTION: Sudamérica es uno de los seis “hotspots” globales de invasión de peces de agua dulce y Chile no es la excepción. Actualmente existen 27 especies introducidas de peces en ecosistemas de aguas continentales. Veinticinco (25) de las 27 exóticas pertenecen a familias no existentes en Chile, siendo Salmonidae, Cyprinidae e Ictaluridae las más abundantes y frecuentes. De esta manera, los peces nativos de Chile (45 especies) se enfrentan a competidores y depredadores desconocidos en términos evolutivos. En este trabajo analizamos principalmente la invasión de salmónidos en Patagonia, especies que luego de un siglo de introducciones, siembras (o sueltas) y escapes, son las más frecuentes en ríos y lagos patagónicos, presentando una amplia distribución tanto latitudinal como altitudinal. Describimos los efectos de los salmónidos sobre las especies nativas, principalmente galáxidos, y analizamos los diferentes mecanismos por los cuales ocurren. Concluimos que las especies nativas son especies “ingenuas” o “naïve”, que parecen no tener las capacidades físicas ni las actitudes comportamentales para contrarrestar o eludir las interferencias negativas de los salmónidos. Por ello, resulta urgente mejorar las actuales medidas de gestión asociadas a las especies introducidas en Chile para proteger la biodiversidad de ecosistemas de aguas continentales.
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    • "The study and management of non-native fish species in emergent economies like Mexico should be a priority due to the positive relationship between the number of nonnative species and economic development (Leprieur et al., 2008). There is an urgent need for studies focused on areas that experience high homogenization of fish fauna such as Central Mexico (Villéger et al., 2011). "
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    ABSTRACT: In Mexico, non-native species are established in virtually every lake and represent one of the most important factors in species diversity loss. An iconic example is Lake Patzcuaro, which used to provide one of the most abundant fisheries of native species among freshwater systems in Mexico. But in the last decades, the relative abundance of non-native species has increased together with a reduction of native species populations. In this study, we analyze the trophic niche overlap between native and non-native species by using carbon and nitrogen stable isotopes. We did not found a spatial effect between physicochemical variables and isotopic signatures. The trophic niche area showed a small overlap among native species, but a substantial overlap of native species with non-native C. carpio and O. aureus. The non-native species P. infans presented almost no trophic overlap with other species. Non-native species have a trophic niche area two times larger than natives. The trophic niche overlap between native and non-native species was higher than among natives. The narrower trophic niche area and the high overlap with non-native species may explain the decline of native species populations. Alternative but untested explanations include altered water quality stemming from pollution and indirect effects of non-natives.
    Hydrobiologia 03/2015; 746(1). DOI:10.1007/s10750-014-1944-z · 2.21 Impact Factor
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    • "In the Neotropical region the spatial distribution of reservoirs is not homogeneous; they are associated with densely populated regions (Pringle et al., 2000; Agostinho et al., 2007; Espínola et al., 2010). Previous works have shown that the number of non-native species that successfully establish in a new community is positively related to the human density of a region (Leprieur et al., 2008; Lockwood et al., 2009; Clavero et al., 2013). However, despite the association of population density and introduction success (Leprieur et al., 2008; Lockwood et al., 2009), there is a growing debate in the literature regarding how the different vectors of species introduction influence the Neotropical fish assemblage composition (Azevedo-Santos et al., 2011; Britton & Orsi, 2012; Lima Jr. et al., 2012; Magalhães & Jacobi, 2013a). "
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    ABSTRACT: Several human activities may result in or facilitate species introductions. In aquatic environments, species introductions are often associated with the construction of dams. In this study, we use reservoirs of the Neotropical region as a model to determine the main causes of fish species introductions. We compiled information on non-native fish species present in reservoir ichthyofauna surveys in the past 14 years and classified these species based on their probable reason for introduction (vector). Fish farming activities introduced approximately 7.6-fold more species in reservoirs than the other vectors identified. The matrix of the number of fish species per vectors explained the greatest proportion of the composition of non-native assemblages, whereas the geographic distance and age of the reservoir explained few of these variations. The non-native ichthyofauna composition varied among Neotropical basins and can be explained by the different sets of species introduced by the companies managing the reservoirs. Although power companies have banned stocking with nonnatives, fish farming in the Neotropical region continues to use non-native species, and these species are occupying water bodies, especially reservoirs.
    Hydrobiologia 03/2015; DOI:10.1007/s10750-014-2025-z · 2.21 Impact Factor
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