Table 7. — Frequencies of meristic counts from juvenile American shad 

 in samples from the York River tributaries, Va. 



-Frequencies of tneristic counts from juvenile American shad 

 in samples from the James River, Va, 







Number of 









Year 



pectoral fin ravs 



Mean 



Standard 





12 13 14 15 16 17 18 19 



deviation 







Frequency 







ramunkev River 



1953 



2 31 17 - 



16.30 



0.5440 



Do. 



1954 



2 24 23 1 



16.46 



0.6131 



Do. 



1956 



4 33 12 1 



16.20 



0.6061 



Do. 



1958 



- 28 22 - 



16.44 



0. 5014 



Mattaponi River 



1954 



2 26 21 1 



16.42 



0.6091 



Do. 



1958 



4 24 22 - 



16.36 



0.6312 





Number of 









dorsal fin rays 









15 16 17 18 19 20 21 22 







Frequency 





Prnimkpy River 



1953 



- 24 25 1 



18.54 



0. 5425 



Do. 



1954 



- 26 22 2 



18.52 



0.5799 



Do. 



1956 



1 21 25 3 



18.60 



0.6389 



Do. 



1958 



3 15 27 5 



18.68 



0.7407 



Mattaponi River 



1954 



1 18 21 10 



18.52 



0.5799 



Do. 



1958 



- 26 22 2 



18.80 



0. 7825 





Number of 









anal fin rays 









13 19 20 21 22 23 24 25 







Frequency 





Rwsnmlrpv IHv?T 



1953 



1 7 27 12 3 



21.18 



0.8254 



Do. 



1954 



- 10 18 20 2 



21.28 



0.8340 



Do. 



1956 



- 7 22 16 5 



21.38 



0. 8545 



Do. 



1958 



- 12 16 20 2 



21.24 



0. 8404 



Mattaponi River 



1954 



- 11 28 10 1 



21.02 



0.7140 



Do. 



1958 



2 14 23 9 2 



20.90 



0.8864 





Number of scutes 







33 34 35 36 37 38 39 40 







Frequency 





Paaimkey Rivpr 



1953 



1 3 14 21 10 1 



36.78 



0.9750 



Do. 



1954 



- 3 14 21 9 3 



36.94 



0. 9742 



Do. 



1956 



2 3 8 18 16 3 



37.04 



1.1599 



Do. 



1958 



- 1 9 28 11 1 



37.04 



0. 7548 



Mattaponi River 



1954 



2 1 12 22 11 2 



36.90 



1.0351 



Do. 



1958 



- 2 11 22 13 2 



37.04 



0.9026 



samples from 1954 and 1958 only, differences 

 in the meristic counts were not significant 

 between locations. Based on the Pamunkey 

 River samples only, differences between years 

 also were not significant (table 9). 



James River . --Mean meristic counts forthe 

 James River samples were similar between 

 years and between locations (table 8). Based 

 on the 1954 samples, counts were not signifi- 

 cant between the two locations, and for the 





Year 



Number of 

 oectoral fin rays 



Mean 



Standard 





12 13 14 15 16 17 18 19 



deviation 



Walcot Wharf 

 Claremont Beach 

 Do. 



1954 

 1954 

 1958 



1954 

 1954 

 1958 



1954 

 1954 

 1958 



1954 

 1954 

 1958 



Frequency 



- 21 28 1 

 1 19 27 3 



- 12 34 4 



15.60 

 15.64 

 15.84 



18.38 

 18.22 

 18.22 



20.70 

 20.62 

 21.00 



36.18 

 36.36 

 36.32 



0. 5345 

 0.6312 

 0. 5481 





Number of 

 dorsal fin rays 







15 16 17 18 19 20 21 22 





Walcot Wharf 

 Claremont Beach 

 Do. 



Frequency 



1 29 20 - 

 5 29 16 - 

 5 32 11 2 



0.5303 

 0.6158 

 0.7083 





Number of 

 anal fin rays 







18 19 20 21 22 23 24 25 





Walcot Wharf 

 Claremont Beach 

 Do. 



Frequency 



17 21 9 3 

 24 21 5 - 

 13 25 11 1 



0.8631 

 0.6667 

 0.7559 





Number of scutes 







33 34 35 36 37 38 39 40 





Walcot Wharf 

 Claremont Beach 

 Do. 



Frequency 



2 6 27 12 2 1 



1 8 20 14 7 - 



2 6 20 18 4 - 



0.9190 

 0.9848 

 0.9355 



Claremont Beach samples the differences be- 

 tween years were not significant. 



Comparison between Chesapeake Bay trib- 

 utaries . --Data for all locations and all years 

 for which collections were available were 

 combined in testing for significant differences 

 in meristic counts between two rivers. There 

 was a significant difference in the meristic 

 counts between the York and James fish in all 

 instances; between the Rappahannock and 

 James, the Rappahannock and York, and the 

 James and Susquehanna in three instances; 

 and between the Rappahannock andSusquehanna, 

 and the York and Susquehanna in two instances 

 (table 9). Where applicable, the interaction 

 between years and rivers was not significant. 

 The differences in meristic counts between 

 rivers indicated that discrete populations of 

 shad occurred in the Chesapeake Bay tribu- 

 taries. 



