Fish Species of Greatest Conservation Need in Wadeable Iowa Streams: Status, Habitat Associations, and Effectiveness of Species Distribution Models

摘要

Freshwater systems are among the most important ecosystems in the world. Approximately one third of all vertebrate species are confined to freshwater which constitutes only 0.8% of the earth's surface (Dudgeon et al. 2006), and a vast majority of this diversity occurs in riverine systems. Freshwater systems are also among the most endangered ecosystems in the world (Dudgeon et al. 2006). The primary threats to freshwater ecosystems and biota include habitat loss and degradation, the introduction of nonnative species, chemical and organic pollution, climate change, alterations to flow (e.g., dams), and overexploitation (Allan and Flecker 1993; Dudgeon et al. 2006). Consequently, many freshwater species are endangered and vulnerable to extinction (Richter et al. 1997; Jelks et al. 2008). For example, 700 North American freshwater and diadromous fish taxa have been identified as endangered, threatened, or vulnerable (Jelks et al. 2008). Additionally, 61 fish taxa are listed as extinct in North America (Jelks et al. 2008) and Ricciardi and Rasmussen (1999) suggested freshwater species extinctions will continue at a rate five times faster than for terrestrial species.