Academic journal article The American Midland Naturalist

Niche Partitioning of the Sympatric Yellowcheek Darter Etheostoma Moorei and Rainbow Darter Etheostoma Caeruleum in the Little Red River, Arkansas

Academic journal article The American Midland Naturalist

Niche Partitioning of the Sympatric Yellowcheek Darter Etheostoma Moorei and Rainbow Darter Etheostoma Caeruleum in the Little Red River, Arkansas

Article excerpt

ABSTRACT.-

We studied how habitat selection influences the distribution and densities of a stenotypic yellowcheek darter Etheostoma moorei (Raney and Suttkus) and eurytypic rainbow darter E. caeruleum (Storer) in a headwater stream subjected to periodic drying. We spatially sampled in habitats within riffle substrates and at four sites four to six times per year in the Middle Fork of the Little Red River. Yellowcheek darters were associated with cobble and gravel more than rainbow darters. Rainbow darters moved along the substrate surface and positioned themselves further downstream in riffles, whereas yellowcheek darters occurred further upstream in or near crevices between gravel and cobble. Neither species was found in the hyporheic zone during riffle drying. The rainbow darters used pools during riffle drying but not yellowcheek darters, which could explain recolonization of previously dry upstream sites by rainbow darters but not yellowcheek darters. Rainbow darters were at their greatest densities in upstream riffles where yellowcheek darters had not recolonized, suggesting niche partitioning. These temporal differences in microhabitat selection appear to enable the coexistence of these two sympatric and ecologically similar darters.

INTRODUCTION

Many darter populations are in decline (Etnier, 1994) with 31% of 147 species considered in jeopardy (Etnier, 1997). Sténotypie niche requirements and endemism are suggested as primary contributors to the high proportion of imperiled darters (Etnier and Starnes, 1991). Habitat preferences for numerous darter species have been investigated both in natural (Chipps et al., 1994; Stauffer et al., 1996; Welsh and Perry, 1998) and artificial streams under controlled laboratory conditions (Matthews and Hill, 1980; Hlohowskyj and Wissing, 1986; van Snik Gray and Stauffer, 2001). A better understanding of habitat requirements of species in declining populations and their relationships to sympatric species can promote sound management decisions.

The Little Red River in north central Arkansas was dammed in 1964, creating Greers Ferry Reservoir. The four headwater streams of the Little Red River, the Middle, South, Beech and Turkey forks, feed the reservoir and historically maintained populations of the yellowcheek darter Etheostoma moorei (Raney and Suttkus) , endemic to these streams (Robison and Harp, 1981) . Approximately 36% of the lower sections of these headwater streams were inundated by the reservoir, representing substantial loss of available habitat for the yellowcheek darter. Conversely, the sympatric rainbow darter E. caeruleum (Storer) occupies a broad geographical distribution through much of the Mississippi River drainage (Page, 1983). Both species occupy high grathent riffles in clear, highly oxygenated water (Winn, 1958; Raney and Suttkus, 1964).

Shortly after Greers Ferry Reservoir filled, the yellowcheek darter in the Little Red River drainage was the most abundant among riffle fishes, and the rainbow darter was third in abundance (Robison and Harp, 1981). Two decades after Robison and Harp's work and following several years of drought with riffle drying and rewetting, the rainbow darter had become the most abundant riffle fish and the yellowcheek darter had declined to fifth in abundance (Wine, 2004). Wine (2004) estimated an 85% numerical reduction and 45% range reduction of the yellowcheek darter since the Robison and Harp (1981) study. Currently, Etheostoma moarei is a candidate species for listing under the Endangered Species Act of 1973 as amended (66 Federal Register 54811).

Our goal was to study niche overlap and distribution between these two sympatric darters within the headwaters of the Little Red River. The rainbow darter has been the subject of much ecological study (e.g., Schlosser and Toth, 1984; Hlohowskyj and Wissing, 1986; Harding et al., 1998), whereas there is a single published article (Wine et al., 2008) investigating the ecology of the yellowcheek darter beyond the original species description of Raney and Suttkus (1964). …

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