Life History, Diet and Habitat of the Federally Endangered Laurel Dace (Chrosomus saylori)

Laurel Dace (Chrosomus saylori) is a small, freshwater minnow that is endemic to headwater streams on Walden Ridge, Tennessee. The species was listed as federally endangered in 2011 and the U.S. Fish and Wildlife Service Recovery Plan indicates a need for life history, diet and habitat studies. A literature review, samples of archived specimens, and a surrogate species, the Tennessee Dace (Chrosomus tennesseensis), were used to describe the life history and diet of the Laurel Dace. A total of 370 Tennessee Dace were collected from Laurel Ford Branch, a stream 8.6 km from the Laurel Dace type-locality, over an 18-month period. The standard length of 370 Tennessee Dace was measured and the age of 72 individuals was determined with otolith microstructure analysis. We examined patterns of growth with a von Bertalanffy model and length relationships. Mortality estimates were derived from model parameters. Tennessee Dace exhibit positive allometric growth, 4+ age groups and estimated annual natural mortality of 73%. Tennessee Dace reproductive biology was determined by identifying and weighing gonads and counting mature ova in all sexually-mature females. The female-to-male sex-ratio was 1.3:1, reproductive maturity began at age-2, and mature ova counts ranged from 64 to 143. Variation in ova maturity between individuals during the March-to-July spawning season indicated that Tennessee Dace are multiple-clutch spawners. Morphometric analysis revealed pectoral fin length-to-standard length ratio as a sexually-dimorphic characteristic. Tennessee Dace and Laurel Dace diets were quantified through multiple season; both species were opportunistic feeders that consumed aquatic and terrestrial invertebrates, plant matter, and algae. The habitat of the northern population of Laurel Dace was characterized in pools in four segments of three streams. Pool volume, water depth, silt depth, canopy cover, and substrate were measured in the field and the sub-watershed land cover of each stream was quantified with ArcGIS. Laurel Dace inhabit streams that are characterized by large pools with predominantly bedrock substrate, dense riparian vegetation and heavily-forested watersheds. The results of this study indicate that to conserve Laurel Dace populations managers may encourage responsible land use on Walden Ridge and change federal permitting to protect individuals during the spawning season.