Spawning Substrate Preferences of the Yazoo Darter (Etheostoma raneyi)

Abstract

The Yazoo Darter Etheostoma raneyi is a small imperiled snubnose darter endemic to Upper Gulf Coastal Plain streams in north-central Mississippi. Installation of rip-rap and wood is being considered in an effort to increase suitable habitat and spawning substrate for the species. In common with other snubnose darters, Yazoo Darters attach their eggs to appropriate spawning substrate. However, it is not known if Yazoo Darters, or other imperiled Coastal Plain snubnose darters, will use rock substrate for spawning given it is almost entirely absent from streams of occurrence. If Yazoo Darters show no preference between wood and rock (rip-rap) for spawning, management would have greater flexibility when designing stream habitat installations for imperiled Coastal Plain snubnose darters, because the installation of rip-rap is much less expensive and time consuming than installation of wood. We used a randomized block experiment in an outdoor mesocosm facility to test for spawning substrate preferences. We counted >7600 eggs and Yazoo Darters used both substrates but used wood more than twice as often as rip-rap. Though we cannot recommend habitat installations using only rip-rap, any installation using a mix of wood and rip-rap will enhance spawning habitat for the Yazoo Darter and at least four other imperiled Coastal Plain snubnose darters.