76 Fred C. Rohde and Rudolf G. Arndt 



Table 1. Average combined monthly gonosomatic ratios (expressed as %) for 

 Cottus bairdi from Butler Mill Branch, Sussex County, Delaware, 1973- 

 1980. Number of specimens in parentheses. 





1973-75 



1978-80 



Month 



Male 



Female 



Male 



Female 



January 



1.52 (4) 



7.57 (20) 







February 



1.40 (2) 



19.51 (3) 







March 



1.05(15) 



20.73 (33) 



0.85 (35) 



16.51 (71) 



May 







0.09 (3) 



0.65(14) 



June 







0.09 (5) 



0.74(17) 



July 



0.21 (5) 



0.57(14) 



0.16 (6) 



0.56(13) 



August 







0.20 (1) 



0.53 (1) 



September 



0.53 (3) 



0.71 (14) 



0.16(14) 



0.49 (5) 



October 



1.21 (7) 



1.46 (4) 







November 



1.26(17) 



2.18(25) 



1.94 (4) 



2.68 (1) 



remained high from November through March. Both sexes in 1978-80 

 showed patterns similar to those of 1973-75. The March 1979 value for 

 females, however, was markedly higher than that of other years, and 

 reflects a later spawning in 1979. 



Fecundity, a general term that refers to number of ova produced, is 

 restricted in this study to the number of mature ova present in the ovaries 

 from January to mid-March. Mean ova number per female (N = 67) is 

 93.7 (range 37-156), and mean female SL is 36.9 mm. The regression 

 equation for the relationship between SL and ova number (Y) is: Y = 

 -157.1 1 + 6.80 SL (Fig. 3). The correlation coefficient, r = 0.90, indicates a 

 strong positive relationship between ova number and SL (P< 0.001). 



Fecundity of the Butler Mill Branch sculpins is low when compared 

 with data for other species of Cottus and for other populations of C. 

 bairdi in Williams (1968), Ludwig and Norden (1969), Patten (1971), 

 Foltz (1976), and Nagel (1980). Exceptions are the diminutive C. pyg- 

 maeus, with a range of 30 to 43 ova (Williams 1968), and C. bairdi from 

 northeastern Tennessee with means of 55.5 to 67.7 ova (Nagel 1980). The 

 low fecundity observed in our specimens and in C. pygmaeus is correlated 

 with their small size, while in the Tennessee population it appears to be 

 correlated with a greater ova size. Females taken in 1978-80 were more 

 fecund (Y = -209.87 + 8.13 SL) than in 1973-75 (Y = -142.24 + 6.46 SL). 

 This difference is significant (0.05 level, testing the slope), and may be a 

 function of size. However, although females in 1978-80 were larger (x SL 

 = 38.2 mm) than in 1973-75 (xSL= 34.5 mm), the difference of the means 

 is not significant. Nagel (1980) noted a similar difference in fecundity 



