An Experimental Study of Vertical Habitat Use and Habitat Shifts in ...

Chapter 2: An Experimental Study of Vertical Habitat Use and Habitat Shifts in
Single-species and Mixed-species Shoals of Native and Nonnative Congeneric
Cyprinids
Abstract
Non-native fishes have multiple impacts on native fish communities, including
impacts associated with competition for space. Watersheds that are historically
depauperate of fish fauna, such as the New River in North Carolina, Virginia, and West
Virginia, are especially susceptible to invasions of non-native fishes. Over 50% of the
fish species currently found in the New River drainage are introduced, including Notropis
telescopus (telescope shiner) and Cyprinella galactura (whitetail shiner). Several studies
have documented vertical water column positioning as the primary mode of habitat
segregation of syntopic cyprinid species. Few studies, however, have examined the
effects of non-natives on vertical habitat use of native cyprinids. The primary objective
of this study was to quantify habitat shifts of two native species of the New River
drainage (Notropis scabriceps and Cyprinella spiloptera) in the presence of non-native
congeners (N. telescopus and C. galactura). Four 246 L aquaria and six vertical position
categories were utilized to experimentally examine shifts in water column positions.
Allotopic trials were conducted to quantify “preferred” positions of individual congener
species and used as controls for comparison with syntopic trials. Tests identified
differences in vertical distributions between allotopic combinations of congeneric pairs,
syntopic combinations of congeneric pairs, and single species allotopic versus syntopic
combinations. Congeneric species of each pair differed significantly in vertical habitat
use. Significant differences also occurred between allotopic and syntopic positions of all
species. Additionally, species of both pairs concomitantly shifted toward mid-water
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