Academic journal article The American Midland Naturalist

Habitat Shift of a Native Darter Etheostoma Olmstedi (Teleostei: Percidae) in Sympatry with a Non-Native Darter Etheostoma Zonale

Academic journal article The American Midland Naturalist

Habitat Shift of a Native Darter Etheostoma Olmstedi (Teleostei: Percidae) in Sympatry with a Non-Native Darter Etheostoma Zonale

Article excerpt

ABSTRACT.-

Etheostoma zonale, the banded darter, was introduced to the Susquehanna River basin of Pennsylvania through an interbasin transfer, or transplantation of native fishes outside their natural range. We examined the habitat use of a darter native to the Susquehanna River drainage E. olmstedi, the tessellated darter, in sympatry and allopatry with E. zonale to determine if its habitat use was different. In the presence of E. zonale, E. olmstedi occupied significantly (P < 0.05) shallower habitats (mean depth < 27 cm) with smaller substrates (mean substrate index < 32) and slower water velocities (mean water velocity < 0.13 m s^sup -1^) than in sites without E. zonale. The habitat shift of E. olmstedi was accompanied by a compression of niche breadth. The results are consistent with the hypothesis that E. zonale excludes E. olmstedi from riffle and run habitats, restricting E. olmstedi to shallow pools and stream margins.

INTRODUCTION

The introduction of non-native fishes has become a global problem (Zaret and Paine, 1973; Courtenay and Stauffer, 1990; Lassuy, 1995; Rahel, 2000). In North America, at least 70 fishes of foreign origin (exotic) have become established in fresh and marine waters (Courtenay et al., 1986; Courtenay, 1995; Courtenay and Moyle, 1996). Most non-native fishes in the United States (150 species), however, are the result of interbasin rather than intercontinental transfers (Courtenay et al., 1986). Interbasin transfers include fishes that have been intentionally or unintentionally transplanted beyond their native range in North America (Moyle et al, 1986; Ross, 1991; Courtenay and Moyle, 1996) and are homogenizing fish faunas in the United States (Rahel, 2000). Although interbasin transfers are much more common than the introduction of exotic species, they are studied less frequently (Ross, 1991). Ecological effects of non-native fishes on native species and communities include habitat alteration (vegetation removal, changes in water quality, Mitchell, 1986), introduction of parasites and diseases (Moyle et al., 1986), trophic alterations (competition for food, prédation, Meffe, 1985; Hindar et al, 1988; Townsend and Growl, 1991; Moyle et al, 2003), hybridization (Hocutt and Hambrick, 1973; Raesly et al, 1990; Leary et al, 1995), spatial alterations (competition for space, Moore et al, 1983; Gatz et al, 1987; Peterson and Fausch, 2003) and extirpation of native species (Schoenherr, 1981; Taylor et al, 1984; Lemly, 1985). Ross (1991) found that the majority of studies (77%) examining effects of non-native species documented a decline of native fishes following the introduction of exotic or transplanted species. In the few cases in which a fish introduction has thought to have no effect, small localized populations or habitats heavily influenced by stochastic events were involved (Moyle et al, 1986; Courtenay and Moyle, 1996; Brown and Moyle, 1997).

Kneib (1972) first collected Etheostoma zonak, the banded darter, from the Susquehanna River drainage in Little Pine Creek, a tributary to Pine Creek, Lycoming County, Pennsylvania, in 1971. Its presence in the Atlantic slope was attributed to a bait-bucket introduction from an Allegheny River drainage population that probably occurred in the late 1960s. In 1972, E. zonale was collected more than 400 km downstream from Little Pine Creek (Denoncourt et al, 1975), perhaps aided by the record flood of Hurricane Agnes in 1972. It is currently the most abundant darter in many localities throughout the Susquehanna River drainage (Raesly, 1991) and has hybridized with E. olmstedi, the tessellated darter (Raesly et al, 1990).

We compared the habitat use by Etheostoma olmstedi in sympatry and allopatry with the nonnative E. zonale to determine if a habitat shift has occurred. We examined microhabitat (on scales of centimeters or smaller, Harding et al, 1998) use because most darters are habitat specialists (White and Aspinwall, 1984; Stauffer et al, 1996) that show few dietary differences (Martin, 1984; Schlosser and Toth, 1984; Gray et al, 1997). …

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