Biology of Etheostoma rufilineatum 75 



Males grew rapidly during the first two years of life and slowed thereaf- 

 ter. The largest male collected was 80 mm (age IV), approaching the 

 estimated maximum length of 88 mm for males. Length-weight relations 

 for male and female redline darters were described by the following 

 regression equations: 



Males log W = -5.42 + 3.32 log |Q L (R 2 = 0.987) 

 Females log io W = -5.11 + 3.14 log^L (R 2 = 0.956) 



where W = weight (g), and L = total length (mm). Both sexes grew at 

 similar rates. 

 Food Habits 



Contents of 546 stomachs were identified and tabulated (Table 3). 

 Empty stomachs made up only 9.9% (range, 5.6 to 11.4%) of the total 

 sample by season (Table 3). Dipteran larvae were the dominant food 

 items throughout the year. Chironomidae and Simuliidae made up from 

 67.1% of the diet in June- August to 87.0% in December- February, and 

 occurred in 10.0 to 83.3% of the stomachs examined monthly. Ephe- 

 meroptera and Trichoptera larvae were important items in summer and 

 fall; 9.8 to 29.3% of stomachs examined from June to November con- 

 tained these larvae. Hydracarina were eaten throughout the year, but 

 were most common in stomachs in March to May (5.1% of the diet). 

 Food of young-of-the-year was not determined, but may have been 

 largely zooplankton, as reported for the young of other species (Scalet 

 1972; Burr and Page 1978, 1979; Page 1980). The food of juveniles 25 to 

 40 mm was similar to that of adults. Items found infrequently in stom- 

 achs (less than 1% of the diet) included Plecoptera, Coleoptera, Nema- 

 tomorpha, and unidentifiable invertebrate eggs. Fish eggs and small 

 crayfish (Decapoda) were found in the stomachs of several large males 

 (60+ mm). 



Sample sizes for the 24-hour feeding studies on 2 July, 13 August, 

 and 9 September were 95, 126, and 98 fish, respectively. Stomach con- 

 tent analyses indicated a distinct feeding chronology and similar feeding 

 patterns on all three sampling dates (Fig. 1). Mean food volumes in 

 stomachs increased from mid-morning through late afternoon and early 

 evening, and decreased from late evening to early morning. Feeding 

 peaks were at 2000 hr on 2 July (0.021 ml/ stomach) and 9 September 

 (0.028 ml/stomach), and at 1600 hr on 13 August (0.027 ml/stomach). 

 None of the fish collected at 1600 hr on the three dates had empty 

 stomachs, but 18 to 30% of those collected at 2400 hr and 76 to 78% 

 collected at 0400 hr were empty. These observations suggest that redline 

 darters are diurnal sight feeders. Scalet (1972) reported that Etheostoma 

 radiosum when feeding may rely on visual cues, particularly on move- 

 ments of prey, and similar visual feeding has been proposed for other 

 darter species (Mathur 1973; Adamson and Wissing 1977; Schenck and 

 Whiteside 1977). 



