Substrate Choice by Three Species of Darters (Teleostei: Percidae) in an Artificial Stream: Effects of a Nonnative Species

Etheostoma zonale, the banded darter, was introduced to the Susquehanna River basin, Pennsylvania, through an interbasin transfer. We examined the effects of darter density and the presence of E. zonale on the substrate choice of two native darter species (Etheostoma olmstedi, the tessellated darter, and Percina peltata, the shield darter) in an artificial stream. In single species trials, E. olmstedi, E. zonale, and P. peltata exhibited nonrandom substrate selection and occupied patches of large substrate significantly (P < 0.05) more often than expected. No intraspecific density effects were observed. The presence of E. zonale did not affect the substrate choice of P. peltata but did induce a shift of E. olmstedi from large to small substrate in high-density trials (P < 0.05). Etheostoma zonale was most frequently the aggressor in behavioral interactions. Neither E. olmstedi nor P. peltata directed any agonistic behavior toward E. zonale; however 40% of aggressive acts initiated by E. zonale were directed toward E. olmstedi and P. peltata. Displacement of E. olmstedi by the aggressor E. zonale suggests potential deleterious effects on the native species.

Fig. 1.

Diagram of the artificial stream, viewed from above (not to scale)

Fig. 2.

Number of Etheostoma olmstedi and Percina peltata observed in small and large substrate patches in single and mixed species trials (including both replicates), illustrating the shift of E. olmstedi to small substrates in the presence of the nonnative Etheostoma zonale. Percina peltata did not exhibit a habitat shift. Abbreviations include o = E. olmstedi, p = P. peltata, and z = E. zonale

Fig. 3.

Number and type of aggressive behaviors per minute initiated by Etheostoma olmstedi, Percina peltata, and Etheostoma zonale. Numbers in parentheses of legend indicate total number of aggressive acts initiated per species

Fig. 4.

Frequency of aggressive behavior directed toward conspecifics and heterospecifics by Etheostoma olmstedi, Percina peltata, and Etheostoma zonale. Numbers in parentheses of legend indicate total number of aggressive acts initiated per species

Fig. 5.

Proportion of Ethoestoma olmstedi, Percina peltata, and Etheostoma zonale individuals observed above substrate, under substrate, and in the water column

Accepted: 28 May 2000