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: 9.34). 03/2008; 6(2):e28. DOI: 10.1371/journal.pbio.0060028
Source: PubMed


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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Available from: Simon Blanchet, Jan 16, 2014
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    • "For example, habitats may become unsuitable for species due to changes in hydrological regimes (Paul and Meyer, 2008; Poff et al., 2006), disruptions to community structure (Pereira et al., 2012), alterations in nutrient cycles (Pereira et al., 2012; Vitousek et al., 1997), the accumulation of pollutants (Gallagher et al., 2014; Laurance et al., 2009; Paul and Meyer, 2008), and the fragmentation or complete loss of habitat (Bar-Massada et al., 2014; Hamer and McDonnell, 2008; McKinney, 2002). Anthropogenic activity can also lead to the introduction of invasive predators, competitors and diseases, which can further reduce species richness (Bar-Massada et al., 2014; Bradley and Altizer, 2007; Laurance et al., 2009; Leprieur et al., 2008; Pereira et al., 2012). Although anthropogenic disturbances often result in a loss of biodiversity , it can also benefit a select few species which are better able to adapt to these environmental conditions, such as crows (Corvus spp.), foxes (Vulpes vulpes), skunks (Mephitis mephitis), and possums (Trichosurus vulpecula) (Bar-Massada et al., 2014; McKinney, 2002). "
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    ABSTRACT: Although human-modified habitats often result in a loss of biodiversity, some have been found to serve as habitat refuges for threatened species. Given the globally declining status of amphibians, understanding why some species are found in heavily modified environments is of considerable interest. We used the endangered green and golden bell frog (. Litoria aurea) as a model to investigate the factors influencing their distribution toward industrial areas within a landscape. The number of permanent waterbodies within a kilometer of surveyed sites was the best predictor of L. aurea occupancy, abundance and reproduction. It appears that industrial activities, such as dredging and waste disposal inadvertently created refuge habitat for L. aurea to fortuitously persist in a heavily modified landscape. Future conservation plans should mimic the positive effects of industrialization, such as increasing the number of permanent waterbodies, especially in areas containing ephemeral or isolated waterbodies and threatened with drought. Our findings also suggest that despite amphibians being relatively small animals, some species may require a larger landscape than anticipated. Recognizing life history traits, in combination with a landscape-based approach toward species with perceived limited motility, may result in more successful conservation outcomes. Identifying why threatened species persist in heavily disturbed landscapes, such as industrial sites, can provide direction toward future conservation efforts to prevent and reverse their decline.
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    • "A growing demand for some ornamental fishes in the aquarium trade and aquaculture is also another threat to fish diversity in Urmia basin which has to be considered. The globalization of trade and communication has made preventing and controlling new introductions extremely difficult because human activities can easily transfer species to different places around the world (Rahel 2007; Leprieur et al. 2008). "
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    • "A classic but largely unappreciated example is Rainbow Trout, a native of the North American Pacific Rim that subsequently dispersed during Late Pleistocene to the Kamchatka Peninsula of the Russian Federation (Behnke 1992). It is now globally invasive and seriously problematic (Halvorsen 2010), with a long history of deliberate recreational stocking, accidental aquaculture escapes, and/or illegal introduction (Leprieur et al. 2008) "

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