Coitus Life History in Delaware 71 



Gonadal development was determined by calculating the gonoso- 

 matic ratio (gonad weight as a percentage of total weight) of 235 

 females and 121 males taken during 1973-80. This sample included only 

 sculpins that could be sexed and with gonads of 0.001 g or heavier 

 (young-of-the-year from September, October, and November collec- 

 tions, and all adults). Gonads were weighed to the nearest 0.001 g. 

 Fecundity of 67 pre-spawning females collected in January (20) and 

 February (3) 1973, March (10) 1979, and March (34) 1980 was deter- 

 mined. Ten ova from each of 57 mature females were measured to the 

 nearest 0.1 mm using an ocular micrometer, and the ova growth rate 

 determined. Deviation from a 1:1 ratio of ova number between right 

 and left ovary in 22 fish was tested with chi-square, as was deviation 

 from a 1:1 sex ratio. Standard length (SL) and total length (TL) were 

 measured to the nearest mm and total body weight to the nearest 0.01 g. 



Eggs were collected where adults were most common. Pieces of 

 concrete block, bricks, and water-logged wood suitable as egg attach- 

 ment sites were provided on 9 March 1980 and 22 February 1981. Color 

 was recorded on live eggs; other data are from preserved eggs. Attempts 

 to collect larvae with a fine-mesh dip net and a 0.5 mm plankton net 

 were made in the same area. 



Age was determined by the length-frequency method. Although 

 otoliths have been used to determine age in sculpins (Koster 1936: Lud- 

 wig and Norden 1969; Patten 1971; Petrosky and Waters 1975), our 

 results using otoliths from both fresh and preserved C. bairdi were 

 inconclusive. The relationship between growth in weight and in length 

 for specimens that could be sexed was determined by fitting a regression 

 line on the logarithms of mean weights and SL for 3 mm intervals. 

 Fitness was determined with the coefficient of condition (K) using the 

 formula K - W X 1Q 5 , where W is weight (g) and L is SL (mm). 

 L 3 



Based on examination of 539 stomachs, we determined the number 

 of food items in five fish SL groups (< 20 mm, 20-29 mm, 30-39 mm, 

 40-49 mm, > 49 mm), and the percent occurrence of food by month. 



Voucher specimens from all localities were deposited in the 

 Academy of Natural Sciences of Philadelphia (ANSP 145647, 145648, 

 and others), and specimens from the Butler Mill Branch locality were 

 also deposited at Iowa State University (ISU 1995, 1996), and the Uni- 

 versity of Florida (UF 30136, 30137). 



STUDY AREA 



The Butler Mill Branch system lies between 8 km northwest and 4 

 km southwest of Seaford, Sussex County, Delaware. It consists of Horse 



