Table 14. --Analysis of variance on meristic counts for differences 

 between locations and between years within rivers, and differences 

 between rivers, for samples of juvenile American shad from 

 South Atlantic coast rivers --Continued 



Rive - 



Component 



Degrees 



of 

 freedom 



F-value 





Between years : 

 (Palatka only) 



2,147 

 2,147 

 2,147 

 2,147 



1,448 

 1,448 

 1,448 

 1,448 



1,448 

 1,448 

 1,448 

 1,448 



1,398 

 1,398 

 1,398 

 1,398 



1,498 

 1,498 

 1,498 

 1,498 



1,448 

 1,448 

 1,448 

 1,448 



1,448 

 1,448 



1,448 

 1,448 



2.732 

 0.068 



Edisto-Neuse 



Between rivers; 

 Between rivers: 



4.763 



23.119** 

 8.469** 



74.019** 

 0.898 



15. 087** 



3.040 

 16.382** 



Ogeechee-Edisto 



Between rivers: 



2.839 



1.305 

 22. 185** 









Sc. Johns-Seuse 



Between rivers: 



12.160** 



16.679** 



3.465 



St. Johns-Edisto 

 St. Johns-Ogeechee 



Between rivers: 

 Between rivers; 



14.738** 



3.196 

 50. 127** 

 130.011** 

 8. 140** 



0.396 

 5.013 















Statistically different at 1 percent level. 



RELATION BETWEEN MERISTIC COUNTS 

 AND OTHER FACTORS 



In certain instances significant differences 

 were found in meristic counts between young 

 shad from neighboring streams and among 

 streams within large geographical areas. 

 Whether the cause of these differences was 

 primarily genetic or was environmental vari- 

 ation under which the fish developed, or a 

 combination of both, would not affect the find- 

 ings. Physical and chemical data on the en- 

 vironment at spawning time were not available, 

 so the relation between differences or shifts 

 in meristic counts between two separate rivers 

 and environmental factors 'was not known. 

 Lindsey (1957), Raney and Woolcott (1955),. 

 and TSning (1952), and others, although working 

 on species other than shad, listed temperature 

 as the obvious environmental factor that may 

 produce differences at the time these charac- 

 ters are formed in the embryo. Although 

 shad spawn earlier in southern rivers and 

 progressively later in northern rivers, widely 

 separated populations spawn and eggs and 

 larvae develop under about the same water 

 temperature range. Laboratory rearing of the 



species under controlled conditions would be 

 needed to demonstrate clearly the relation 

 between meristic counts and temperature. 



There was no consistent latitudinal cline 

 in the meristic counts examined over the en- 

 tire geographic range sampled. Fin ray counts 

 were higher in southern rivers and lower in 

 northern rivers, with intermediate counts in 

 between. Scute counts were higher in northern 

 rivers and lower in southern rivers. The Con- 

 necticut River samples had the lowest mean 

 count in pectoral and dorsal fin rays, and the 

 St. Johns River samples had the highest mean 

 counts in dorsal and anal fin rays. However, 

 the mean scute counts, which showed the 

 greatest difference, reversed this pattern with 

 the high in the Hudson River being more than 

 one unit larger than the low counts in the 

 Neuse River. 



There were slight variations in meristic 

 counts on juvenile shad between years and lo- 

 cations within a river, but these were not 

 significant and ■were small compared to the 

 differences in the counts between rivers. The 

 differences in meristic counts between rivers 

 indicated that discrete juvenile populations 

 exist. For a better understanding of shad 

 populations, future work should include studies 

 of the relation between the meristic counts of 

 juvenile shad and environmental variations 

 under which the fish developed. 



SUMMARY 



To test if shad populations in various rivers 

 could be separated by differences in meristic 

 count, collections of juvenile shad from 10 

 rivers along the Atlantic coast were compared 

 by analysis of variance. Counts of pectoral, 

 dorsal, and anal fin rays and scutes were used. 



Differences in counts of meristic charac- 

 teristics 'within individual rivers and between 

 rivers within geographical areas were as 

 follows : 



1. Within individual rivers, no significant 

 differences were found between locations and 

 between years except between locations for 

 pectoral fin rays in the Connecticut River. 



2. In the North Atlantic area, significant 

 differences were found between the Hudson 

 and Connecticut Rivers for all counts except 

 anal fin rays . 



3. In Chesapeake Bay tributaries, signifi- 

 cant differences were found between the York 

 and James Rivers for all counts; between 

 the Rappahannock and James Rivers, the Rap- 

 pahannock and York Rivers, and the James 

 and Susquehanna Rivers for three of the 

 counts; and between the Rappahannock and 

 Susquehanna, and the York and Susquehanna 

 Rivers for two of the counts. 



4. In the South Atlantic area, significant 

 differences were found between the Neuse and 

 Edisto Rivers, and the Neuse and St. Johns 



