70 Fred C. Rohde and Rudolf G. Arndt 



its tributaries, near Seaford, Sussex County, Delaware, during 1973-75 

 and 1978-81 and report here on habitat, reproduction, age and growth, 

 food habits, and abundance. Franz and Lee (1976) reported on a popu- 

 lation in Caroline County on the Eastern Shore of Maryland, 4.0 km 

 north of Federalsburg and 15.2 km northwest of Butler Mill Branch, 

 and briefly considered habitat, food habits, and size. In spring 1981 we 

 discovered a third population, in upper Sullivan Branch and the lower 

 parts of its tributaries, Wolfpit and Raccoon branches, 6.4 km north of 

 Federalsburg, Caroline County, Maryland, and a fourth in Skinners 

 Run, at a point just upstream of Route 307 and 4.0 km southwest of 

 Federalsburg, Dorchester County, Maryland. All data herein refer to 

 the Butler Mill Branch population, unless otherwise specified. 



MATERIALS AND METHODS 



Specimens of C. bairdi (N = 1009) were collected with a 3.0 m X 1.2 

 m, 3.2 mm mesh nylon flat seine. All habitats were sampled. Collections 

 were made on 28 October and 4 November 1973; 20 January, 17 Febru- 

 ary, 17 March, 20 July, 8 September and 30 November 1974; 2 and 23 

 March 1975; 7 September and 26 November 1978; 16 March and 25 

 July 1979; 9, 15, 22 and 30 March, 13 April, 4 and 20 May, 8 and 28 

 June, 12 and 25 July, and 9 August 1980; and 22 and 27 February, 7, 

 14, 22, 26 and 29 March, 5, 11, 18 and 25 April, and 19 May 1981, 

 between 1050 and 2000 hours. Fish were preserved in 10% formalin and 

 stored in 40% isopropyl alcohol until examined. For conservation pur- 

 poses, the last specimens taken in each collection, regardless of sex, size, 

 and reproductive condition, were usually released. Through 1979, only 

 relatively small samples were taken, because of the presumed small size 

 of the population. Sampling was intensified in 1980 and 1981 to pin- 

 point spawning time, locate eggs, and collect larvae. In 1981, fish were 

 primarily observed in the field, and most of those collected were 

 released alive. 



An additional 41 adult C. bairdi were taken by seine in spring 1981 

 at the new Caroline County locality, 6 adults at the Dorchester County 

 locality, and 1 adult at the locality given by Franz and Lee (1976); these 

 were preserved. 



Air and water temperature, pH (Hach Kit), and dissolved oxygen 

 (Yellow Springs meter) were recorded at time of capture. To help char- 

 acterize the habitat in areas particularly frequented by C. bairdi, semi- 

 quantitative substrate samples of about 8 liters were taken from Butler 

 Mill Branch and about 1.2 liters from an upper tributary. The samples 

 were dried and sieved, and the percentage by weight of several gravel/ 

 sand particle size categories determined. 



