Figure 5. — Holding pen for experimental fish in Snake Island fishway attraction chamber. 



species stayed nearer the bottom. Occa- 

 sionally two or three shad left the calm 

 waters, moved into the attraction flow, and 

 swann upstream in the current toward the 

 fishway entrance, only to veer off into the 

 calm water about Z feet short of the fishway 

 entrance. The behavior of the fish did not 

 change significantly during the various com- 

 binations of attraction flow. 



Study of the River Above the Dam 



Approximately 490,000 fertilized shad eggs, 

 obtained May 24 to June 12 from commercial 

 fishermen at Gunston Hall, were distributed 

 above Little Falls in hatching boxes of vari- 

 ous colors (fig. 6). About 50 percent of the 

 eggs were placed in boxes about 2 miles 

 above Little Falls, 15 percent about 6 miles 

 above Little Falls, and 35 percent at Great 

 Falls. Survival of eggs to the eyed stage 

 ranged from 20 to 85 percent and averaged 

 58 percent. Survival of eggs to the eyed 

 stage in black and unpainted boxes aver- 

 aged 73 percent, but in white-painted boxes 

 averaged 48 percent. Peak hatching of all 

 lots occurred in about 68 hours at water 

 temperatures of 23 to 25 C. At water tem- 

 peratures of 18° to 20° C., eggs hatched 

 in about 88 hours. Hatching survival did 

 not differ among locations. 



Figure 6. — Shad eggs in hatching boxes above Little Falls, 

 Potomac River. 



A search was made for young shad August 

 20-23 at the hatching sites above Little Falls 

 Dam. Shadlike feeding activity was seen at 

 hatching sites about 2 and 4 miles above the 

 dam, but not at the other sites. Boulders 

 and shoal areas prevented sampling with 

 trawls in the area where the fish were active. 

 Seven young shad, from 2.9 to 3.5 inches 

 fork length, were collected by trawl in the 



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