separation" (and intergradation) of Ginsburg 

 (1938). 



In all tables the upstream localities are 

 at the top, and all east shore tributaries of Chesa- 

 peake Bay are followed by an asterisk . The 

 term "Upper Bay" refers to the region north of 

 the Rappahannock River. Data for the James 

 River include stations within its large tributary, 

 the Chickahominy River. In tables listing James 

 River samples the number following the local- 

 ities such as J29 and C43 indicate the distance 

 in nautical miles from the mouth of the James 

 River. 



RESULTS 



Spines in First Dorsal Fin- The dorsal fins 

 are separate . The membrane attached to the 

 posteriormost spine of the first dorsal fin termin- 

 ates on the dorsum well in front of the origin of 

 the second dorsal fin . On gross examination all 

 ray elements in the first dorsal fin seem to be 

 spines, viz., single, median, unsegmented, 

 sharp, and hardened structures . It does not ap- 

 pear likely that an increase in number of spines 

 in the first dorsal fin is caused by a shifting 

 forward of a spine from the second dorsal fin 

 because the latter invariably contains one spine 

 which is situated anteriorly. 



The counts were made using adequate mag- 

 nification. The most anterior spine may be 

 small and sometimes is close to the next best 

 developed spine; however, no attempt was made 

 to dig into the skin or muscle at the origin of 

 the dorsal fin. It seems liKely that this small 

 spine might easily be overlooked in larger juven- 

 iles or adults, and it is probable that it may 

 regularly become buried in the flesh. The 

 posteriormost spine in the first dorsal fin is 

 normally not much smaller than the penultimate 

 spine but is more recumbent. It is easily sighted 

 when the anterior spines are pulled upright . 



In order to determine if there is an in- 

 crease in number of first dorsal spines with 

 size, the standard length of young specimens 

 with 9 or fewer dorsal spines was compared 

 with those having 10 or more which were taken 

 in the James River in 1954 (table 1). The mean 

 values are not statistically different. 



Throughout the range of the striped bass 

 the modal number of spines in the first dorsal 

 fin is 9. The range is 7 to 12 with 10 being the 

 second most frequent count; 8 and 11 spines are 

 counted infrequently and 7 and 12 occur rarely. 

 When a shift occurs it is from 9 toward 10 rays. 

 Therefore those with a higher mean value gener- 

 ally have a greater variance. 



In the earlier studies of races in striped 

 bass by Raney, et al (1953, 54, 55), the number 

 of first dorsal spines seemed of little value . 

 However, after the numerous series of young 

 obtained in the summers of 1954 and 1955 from 

 many tributaries of Chesapeake Bay were counted 

 it was noted that those from the James River 

 system averaged high and a check of this char- 

 acter in other Atlantic Coast samples showed 

 this to be an unusual count which was approached 

 only by samples from the Hudson River. 



The first dorsal spine number is rather 

 constant within the James and Hudson, the only 

 two rivers where adequate samples were avail- 

 able from several localities . The frequency 

 distributions of samples taken in July, 1955 from 

 six localities in the James River are given in 

 table 2 . The extreme localities are separated 

 geographically by a distance of approximately 

 30 nautical miles. No trend is noted for the 

 mean values and chi- square shows no significant 

 difference at the 5 percent probability level and 

 indicates that all samples could have been drawn 

 from the same population . A composite sample 

 from two upstream localities in the James River 

 is compared with that from four downstream 

 localities (table 3); a test indicates that the two 

 samples are not significantly different at the 5 

 percent level. An analysis for spine counts of 

 young taken on July 23 and 24, 1954 (table 4) gave 

 similar results. A high dorsal spine count was 

 obtained from a sample taken in the Chickahominy 

 River at Shackleford Farm near Lanexa in 1954 

 (table 5) was compared with a down-river sample; 

 a test indicates a statistically significant differ- 

 ence. This upstream high count may represent 

 an unusual sample but in any event it is different 

 in the direction in which the James sample is 

 specialized. A sample of 21 young taken at 

 Shackleford Farm on July 26, 1949, had a mean 

 value of 9 . 19 which is more nearly in line with 

 expected values . 



88 



