Introduction of non-native freshwater fish can certainly be bad

We wish to accept Gozlan’s (2008) invitation: ‘The aim of this paper is to open a critical debate on the real threat posed by the introduction of non-native fishes’ (p. 107). Gozlan (2008, p. 106) states that: ‘Here I show that on the global scale, the majority of freshwater fish introductions are not identified as having an ecological impact while having great societal benefits.’ We strongly disagree with this statement, which is Abstract In this paper, we respond to Gozlan’s views of the introduction of freshwater fish, as we strongly disagree with his view and approach. We demonstrate that many realworld examples of freshwater fish introductions have catastrophic ecological consequences. We detail a few noteworthy examples, such as those of the Nile perch, carp, tilapias, catfishes, and the zebra mussel. We discuss within-nation introductions, and we explore several related problems, such as hybridization and spread of pathogens and parasites. We propose that Gozlan’s analysis is biased, as more reliable data on impacts that are already widespread are urgently needed, mainly in the biologically richest areas of the world. Thus, we continue to advocate the precautionary principle, because species introductions, once established, are largely irreversible.