Biology of the Blackside Dace Phoxinus cumberlandensis

Abstract

The biology of the blackside dace Phoxinus cumberlandensis (Cyprinidae) was investigated in the upper Cumberland River drainage in 1977, 1978 and 1981. The dace inhabited small, cool upland tributaries which have near equal riffle-to-pool ratios where it frequented pool areas having extensive cover. It occurred sporadically in the Cumberland Mt. region and was more generally distributed in the Cumberland Plateau area. Sand followed by periphyton and organic detritus constituted the major contents of the digestive tract. Macroinvertebrates generally occurred infrequently but were the entire diet in winter. Diet changed seasonally but did not change with size or age. Pimephales notatus and Campostoma anomalum were the only associated species whose diet appeared to overlap with Phoxinus cumberlandensis. Based on the presence of mature eggs, spawning began in April and extended perhaps as late as July. Fecundity averaged 1540 ova/female. Spawning occurs over gravel nests of the stoneroller minnow Campostoma anomalum. Blackside dace appear to have a life span of 3 years with females having greater survivorship; growth is rapid in both sexes the 1st year but slows the following years with females having the slower rate. Phoxinus cumberlandensis is considered a threatened species due to habitat degradation related to surface mining. INTRODUCTION The blackside dace Phoxinus cumberlandensis, recently described by Starnes and Starnes (1978), is known only from isolated, small upland streams in the upper Cumberland River drainage of Kentucky and Tennessee, mostly above Cumberland Falls. It displays brilliant coloration, particularly when in nuptial condition, and is among the most ornate of all cyprinids. The species is considered threatened due to degradation of habitat in the upper Cumberland drainage by coal surface mining. STUDY AREA AND METHODS The main study area, Young's Creek, located 10 km NNW of Williamsburg, Whitley Co., Kentucky, is a small upland stream (altitude 265-340m) flanked by fields and deciduous forest. A belt of mature deciduous trees and hemlock with interlocking canopy borders the stream. With this cover, stream temperatures rarely exceed 23 C. In dry weather, water clarity ranges from clear to slightly murky. Substrate varies from cobble and bedrock slabs in riffles to rubble, boulders and sand in pools, with negligible to moderate siltation. Riffles vary in depth from 5-15 cm, pools from 15 cm-1 m deep. Blackside dace were usually associated with undercut banks, rock slabs or brush in pools and gentle runs. Additional observations were made in Little Clear Creek, Bell Co., Kentucky, which is overall similar in local habitat characteristics but has a slightly higher gradient and offers more limited reaches of habitat. Sampling was conducted in Youngs Creek April-October 1977, December 1977 and March 1978; excessive flooding prevented sampling in November 1977 and thick ice cover prevented sampling in January-February 1978. Population estimates for blackside dace were made from September collections using sodium cyanide. Three 15-m sections of the stream were sampled; 50 specimens were retained for age and growth studies and the remainder were returned alive to the stream. Because of their threatened status, and because of complicated procedures for studying the relatively unvaried detritivorous diet, monthly seine samples of dace for diet studies were limited to 10 specimens though larger samples were taken in some months for other studies. Syntopic species were also taken for comparison. Supplementary observations on feeding and spawning activities were made in Little Clear Creek in May 1981.