pool above Little Falls Dam. Undoubtedly 

 these fish were from shad eggs hatched 

 above the dam. 



CONCLUSIONS 



Our observations at the Snake Island fish- 

 way during four seasons proved that it passed 

 resident species such as suckers, carp, cat- 

 fish, bluegills, and crappies. No anadromous 

 fishes, so far as could be determined, as- 

 cended the river to the fishway. Measure- 

 ments of water flow and levels in the fish- 

 way indicated that it operated as designed. 

 I believe that since the resident fishes nego- 

 tiated the fishway, the anadromous species 

 also surely would have done so if they had 

 been present. 



The failure of the experimental fish to use 

 the fishway is unexplained. Possibly the hold- 

 ing facility in the attraction chamber was 

 too snnall, and therefore the fish remained 

 excited and unschooled. It also is possible 

 that the presence of several species in the 

 attraction chamber at one time may have 

 prevented normal reorientation and behavior. 

 Mortality in the holding facility was un- 

 usually high; it may be necessary in future 

 holding experiments to use the entire at- 

 traction channel to hold experinnental fish. 

 This arrangement would aprovide a holding 

 facility about 120 feet long by 45 feet wide. 

 Attraction flow could continue to be regu- 

 lated by the stoplog structure. 



I feel that the attempt to pass shad and 

 other anadromous fish at Little Falls failed, 

 not through any fault of the fishway, but as 

 a result of failure of the fish to migrate 

 that far upstream. Why anadromous fishes 

 do not ascend the river to the fishway is 

 not readily apparent. It is possible that: 



(1) the runs, particularly of American shad, 

 are at such a low level that the spawning 

 area above Little Falls Dam is not needed, 

 and therefore the fish are not compelled 

 to move as far upstream as in former years; 



(2) the stocks with the urge to nnove above 

 Little Falls Dam (if they existed as a dis- 

 tinct genetic unit), which were blocked from 

 their natural spawning grounds when the dam 

 was rebuilt (1943-49), have since disappeared; 

 and (3) the rapids immediately above Chain 

 Bridge may deter the upstream progress 

 of migrating fish, at least at some river 

 discharges. 



The commercial catch of shad in the Potomac 

 River has declined (fig. 7), with minor fluc- 

 tuations, fron-i a peak of more than 3 million 

 pounds in 1922 to less than one-quarter of 

 a million pounds in 1963 (Powers, 1958; 

 Lyles, 1965). The establishment of runs be- 

 yond Little Falls Dam could aid in the 

 restoration of the fishery. Successful pas- 

 sage of shad by the fishway could produce 



1890 1900 1910 1920 1930 1940 1950 I960 1970 

 YEAII 



Figure 7. — Commercial shad catch, Potomac River, 

 1890-1964. 



benefits after a period of 8 to 10 years from 

 the added spawning habitat above Little Falls. 



In the framing of plans to restore runs of 

 anadromous fish, particularly American shad 

 and striped bass, to the area above Little 

 Falls, it is important to consider that each 

 river, possibly each spawning area, sup- 

 ports a self-perpetuating population that re- 

 turns each successive generation to spawn 

 in the same area (Mansueti, 1961; Nichols, 

 I960; Talbot and Sykes, 1958). The upper 

 limits of the present spawning grounds of 

 shad and striped bass are near Gunston 

 Hall, about 25 miles below Little Falls Dam 

 (Mansueti and HoUis, 1963; Walburg and 

 Nichols, 1967). 



Success in reestablishing runs of anad- 

 romous fish above Little Falls Dam, there- 

 fore, may require the transplantation of fer- 

 tilized eggs from the lower to the upper 

 river to build up a population that will have 

 the instinct to move above the dam each 

 spawning season. Successful hatching of shad 

 eggs in the river above Little Falls and col- 

 lection of young shad in the Little Falls pool 

 indicated that the area can support runs of 

 shad. 



The fishway, with its auxiliary water supply 

 and stoplog feature for controlling the attrac- 

 tion water, is an excellent facility for the 

 study of the behavior of the anadromous fish; 

 findings could have immediate application 

 in the planning of fish passage elsewhere. 

 The experience gained can provide guide- 

 lines for continued studies. 



ACKNOWLEDGMENT 



The Washington District Army Corps of 

 Engineers provided excellent cooperation 

 during the fish-passage studies at Little Falls 

 Dam. 



13 



