NOTE Bilkovic et al : Spawning of Alosa sapidissima and Morone saxattlts 



637 



Mattaponi River: American Shad 



50 T 

 40  

 30- 



LJJXtJlJlJlilJuJLaJJUi^ 



128 120 113 105 98 91 83 76 68 

  egg D'a^ae 



Q Mattaponi River: Striped Bass 



600 

 500 

 400 

 300 

 200 

 100 

 



—aujJjU 



128 120 113 105 98 91 83 76 68 



I egg p^ larvae 



Pamunkey River; American Shad 



10 T 



8 



2 



154 143 131 124 113 104 94 83 72 



 egg Dla^^ae 

 Pamunl<ey River: Striped Bass 



1200 

 1000 

 800 ' 

 600 

 400 

 200 

 



■i^-i^-<-j ^ »ii fc -i»^«ri-^*^-<- 



154 143 131 124 113 104 94 83 72 

  egg □ larvae 



Stations (km from mouth of Yorl< River) 



Figure 4 



Total American shad and striped bass density (eggs and larvae) distinguished by river, species, and 

 life stage for 1997-99 bongo and pushnet collections. Note differences in scaling on the y-axis. 



tributary volume alone is responsible for the contrasting 

 patterns. Instead, differences in discharge, river sinuosity, 

 habitat, stock size, or combinations of these factors may 

 be responsible. 



Temporal and spatial overlap in spawning distributions 

 of American shad and striped bass occurs in the York 

 River system but the primary spawning grounds of these 

 species are disjunct. Evidence of spawning and peak egg 

 abundance for both species was apparent throughout the 



water temperature range of 13-19°C in both rivers. Trends 

 of general abundance for both years and rivers indicated 

 that American shad spawn in regions upstream of striped 

 bass primary spawning grounds (Fig. 4). Trophic interac- 

 tions, especially predation and competition, may explain 

 the disjunct spawning habitats of these species in the York 

 River Striped bass may be important predators on Ameri- 

 can shad in freshwater (Mansueti and Kolb, 1953; Walburg 

 and Nichols-'). Although recent studies have failed to detect 



