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Large losses of wetlands have led many private organizations as well as state and federal agencies to implement restoration programs. Restored wetlands are often highlighted for their value as critical refugia for unique communities of native aquatic and semi-aquatic vertebrates, aquatic invertebrates, and hydrophytes. Approximately one third of the nation's endangered species are dependant on wetland habitats (U.S. Fish and Wildlife Service 1990). However, in a broader sense, prairie wetland restorations are intended to ameliorate results of earlier losses by reestablishing unique ecological functions of wetland basins in the prairie ecosystem. Unfortunately, there is little available information describing functional results of these wetland restorations (Kusler and Kentula 1990).

Wetland restoration provides unique opportunities to observe ecological processes and evaluate human uses of wetlands that may threaten development and sustainability of native communities and natural processes (or "ecological integrity", sensu Grumbine 1994). Throughout the PPR, commercial fish rearing in semipermanent wetlands occurs on a large scale. Litvak and Mandrack (1993) reported sales of cultured and wild-harvested bait fish from nine states exceeded $367 million in 1991. Fathead minnows (Pimephales promelas) are commonly reared for sale as bait fish in semipermanent wetlands in the Midwestern U.S. (Peterson and Hennagir 1980). Fathead minnows are native to prairie wetlands (Peterka 1989) but winter hypoxia frequently limits their populations. Annual stocking may circumvent natural density fluctuations and sustain dense minnow populations. Thus, through such human intervention, this species has potential to impact biological communities in ways more characteristic of exotic invaders (Lodge 1993).

Ecological consequences of these and other fish introductions to prairie pothole wetlands are poorly known. Little biological data is available upon which to base restoration strategies, or to guide state and federal wetland managers who develop and implement regulations about private and commercial uses of natural and restored wetlands. It is likely that dense populations of fathead minnows reduce ecological integrity of restored and natural prairie wetlands. Given the key roles of fish in other aquatic systems, fathead minnows in wetlands may: 1) prey on and reduce abundance of aquatic invertebrates (Brooks and Dodson 1965, Crowder and Cooper 1982, Hanson and Riggs 1995), 2) compete with native species of birds for food resources (Swanson and Nelson 1970, Eadie and Keast 1982, Deutschman and Peterka 1988, Cox et al. 1998 ), 3) increase nutrient availability, planktonic algae, and sediment resuspension (Meijer et al. 1990, Hanson et al. 1995, Vanni and Layne 1997), and 4) limit native submersed macrophyte communities (Scheffer et al. 1993, Hanson and Butler 1994). Through these mechanisms, fathead minnows may alter ecological characteristics and lower quality of wetlands as habitat for wetland-dependant species of animals and plants. Restored wetlands may be especially vulnerable to minnow influences if they are biotically depauperate from prior draining, tillage, or other activities. Here, fathead minnows may delay or impede development of natural communities and processes, limiting biological success of restoration efforts.

Broad objectives of this study are to: 1) identify potential influences of fathead minnows on communities and ecological functions of both nondrained and restored wetlands, 2) clarify roles of fathead minnows in limiting reestablishment of these communities and processes in restored wetlands, and ultimately, 3) document recovery potential of impacted wetlands via removal of dense minnow populations, and 4) assess biological success of wetland restoration. Our results will provide biological information for state and federal wetland management agencies so that ecologically-based management policies regarding fathead minnows and restoration strategies can be further developed.