ABSTRACT
Regardless of the small proportion of the Earth’s surface occupied by fresh water (<2.5 per cent sensu Costanza et al, 1997), these systems are among the most likely locations for successful species invasions due to the frequency, duration and magnitude of anthropogenic impacts (Costanza et al, 1997; Gherardi, 2007; Rahel, 2007). Consequently, rivers and lakes have featured in some of the earliest and most well-documented case studies of IAS reported in the literature. It is perhaps telling that of the seven case studies that Elton (1958) uses to introduce his seminal monograph on species invasions, four are broadly freshwater (including estuarine) taxa: Anopheles gambiae (or rather Anopheles arabiensis) (Parmakelis et al, 2008), Spartina townsendii (Townsend’s cordgrass), Petromyzon marinus (sea lamprey) and Eriocheir sinensis (Chinese mitten crab). In the IUCN’s 100 Worst Invasive Species list, compiled in 2000, 23 are primarily associated with freshwater ecosystems (rising to 50 if more generalist species that are also found in riparian zones are included), which is again a substantial proportion relative to the proportional abundance of these ecosystems (Lowe et al, 2004).
