Population densities and habitat affinities of the threatened blackside dace (Phoxinus cumberlandensis)

Tyler R. Black and Hayden T. Mattingly

Department of Biology, Box 5063

Tennessee Technological University

Cookeville, TN 38505, USA

trblack21@tntech.edu

Abstract.  The blackside dace, Phoxinus cumberlandensis Starnes and Starnes, 1978, is a rare cyprinid restricted to small tributaries in the Upper Cumberland River system in southeastern Kentucky and northeastern Tennessee.  The objectives of this study were (1) determine presence-absence and population densities of Phoxinus cumberlandensis within its historical range and (2) to validate the effectiveness of logistic regression habitat models to predict P. cumberlandensis presence/absence within the Upper Cumberland drainage.  In the most recent sampling phase in 2005, forty-four

200-m reaches within 26 streams throughout the historical distribution of the blackside dace were sampled via single-pass backpack electrofishing.  Blackside dace were found to inhabit 16 of 26 streams and 23 of 44 reaches; although, most reaches (73%) had catch rates of £ 10 dace per 200 m.  For reaches where blackside dace were present, single pass electrofishing catch rates ranged from 1 to 96 fish (mean ± SD = 23 ± 27).  Petersen mark-recapture population estimates were conducted on six of the reaches within six streams and estimates ranged from 54 to 613 dace per 200 m reach.  Population estimates were used to build a regression model to calibrate the single-pass electrofishing for the other 17 reaches inhabited by dace.  Environmental variables (conductivity, dissolved oxygen, temperature, and turbidity) were measured at all 44 reaches to enable validation of previously developed logistic regression habitat models.  Validation of models is currently in progress.

Keywords: Phoxinus, habitat modeling, endangered species conservation, population estimation, mark-recapture