Aquatic Ecosystem Health as Indicated by the Number of Non-Native Fishes

Non-native species change ecosystems, even if only temporarily.  If these changes result in ecological or economic disruption or adversely affect human health, then the species is generally considered invasive and may be useful as an indicator of threats to ecosystem health.  Spatial and temporal trends in the number of non-native aquatic species in the United States might be useful, therefore, as a indication of aquatic ecosystem health.  However, efforts to develop such trends have reportedly been thwarted by inadequate data.  The objective of this paper is to examine the utility of the American Fisheries Society’s (AFS) lists of fish names for determining trends in the number of established non-native fishes in the continental United States for possible use as an indicator of ecosystem health.  As of 2004, there were 65 non-native species established in the continental United States, a 2.5-fold increase from 1970.  All of the species except one, established before 2004 persisted in 2004 (i.e., once established, always established).  The number of non-native families increased from 8 to 19 during the same period.  Converting a trend in the number of non-native species into conclusions about ecosystem health is problematic.  Current knowledge of non-native species impacts on ecosystems, relative to societal desires and goals for ecosystems (other than biodiversity), is incomplete, and warrants additional research.