Natural depressional wetlands in the floodplain are part of the mosaic of aquatic habitats important to stream fishes. Livestock watering holes (i.e., dugouts) are constructed in floodplains, yet the influence of these manmade wetlands on native stream fishes is unknown. Such information is important for the management of native stream fishes, such as the endangered Topeka shiner (Notropis topeka). The goal of this study was to suggest technical guidelines for constructing floodplain wetlands that are compatible with stream fish resources. Specific objectives included: (1) determine fish use of dugouts in the Six Mile Creek watershed; (2) develop models of floodplain inundation; (3) characterize water quality, morphometry, and placement of dugouts; (4) associate fish community and population characteristics with dugout characteristics; and, (5) provide recommendations for dugout construction to enhance compatibility with stream fish resources and to avoid adverse effects on the Topeka shiner and its habitat.
Twenty dugouts spanning Six Mile Creek watershed were sampled for fishes. Dugouts were monitored for water quality and categorized according to connectivity with the stream, distance from the stream (m), flood frequency, stream order, and upper-lower basin location.
Fishes were sampled in dugouts and adjacent stream reaches with seines (4.8-mm bar mesh) and traps. All captured fishes were identified and tallied. Total lengths (mm) and weights (g) were obtained from Topeka shiners and the three most abundant co-occurring species. Calculated community metrics included: species richness, species diversity (Shannon's Diversity Index), and relative abundance. Fulton-type condition (KTL) was calculated for Topeka shiners. A sample of predator fishes was collected for diet analysis from a disconnected dugout containing the Topeka shiner.
Relationships between variables were tested using the t-test, Mann-Whitney U Test, and linear and logistic multiple regression. Dependent variables included Topeka shiner presence, fish presence, Topeka shiner abundance, fish abundance, and fish diversity. Independent variables included dugout placement categories, water quality, and the following fish community variables: species richness, species diversity, fish abundance, sunfish abundance (includes orangespotted sunfish [Lepomis humilis], green sunfish [Lepomis cyanellus], and total sunfish), sunfish presence (orangespotted sunfish, green sunfish, and total sunfish), fathead minnow (Pimephales promelas ) abundance, and fathead minnow presence.
Fish assemblages of dugouts (22 species) and the stream (20 species) were similar. Fish inhabited 13 of 20 dugouts; seven of 20 contained Topeka shiners. Three dugouts contained Topeka shiners each year from 2003 to 2005 and two dugouts (SMC-06 and SMC-15) contained Topeka shiners during all seven sampling seasons. Highest Topeka shiner catch for dugouts SMC-06 and SMC-15 were 142 and 133, respectively. Both SMC-06 and SMC-15 were close to the stream (<15.2 m), frequently flooded, and remained disconnected throughout the study. Three year classes were present in SMC-06 from 2003 to 2005 and in SMC-15 from 2004 to 2005. However, it is likely that the "missing" year class in SMC-15 during 2003 was the age-0 fish that were too small to be captured with a 4.8-mm mesh.
Fish presence (Z=3.25; p=0.001) was higher in dugouts than the stream, but there was no difference in species richness (Z=1.77; p=0.08) or relative abundances of fishes (Z=-1.08; p=0.28) between dugouts and the stream. Significant differences in presence and abundance of Topeka shiners and other species were found among the dugout placement categories, an important relationship being greater Topeka shiner abundance in frequently flooded dugouts (H=11.87; p=0.0027) compared with very frequently or occasionally flooded dugouts. Longitudinal placement of dugouts in Six Mile Creek watershed was not significant in predicting Topeka shiner presence. No significant relationships were observed between dugout water quality variables and Topeka shiner presence; however, fish presence (i.e., all species included) was predicted by dissolved oxygen concentration (stepwise logistic regression; p=0.015). Topeka shiner presence in dugouts was positively related (stepwise logistic regression) to species richness (p<0.001) and orangespotted sunfish abundance (p<0.019) and negatively related to abundance of all fishes (p=0.027). Topeka shiner abundance in dugouts was positively related (stepwise linear regression) to green sunfish presence (p<0.001) and fathead minnow presence (p=0.007). No significant effects of predators on Topeka shiners in dugouts were observed. Topeka shiner use of off-channel habitats has been found in other studies. My results suggest that constructing dugouts separate from the stream within frequently inundated zones can provide off-channel habitat for fishes.
The best option to avoid Topeka shiner entry into a dugout is to place the dugout outside the 100-year floodplain. Within the floodplain, disconnected dugouts constructed in very frequently flooded or frequently flooded zones, within 15.2 m (50 ft) of the stream, below the groundwater level, and in drainages with contributing watershed greater than 809.4 ha (2,000 ac) can provide important habitat for the Topeka shiner.