FISH PASSAGE AND THE SPORT FISHERY 

 BELOW THE DAM, 1960 



Observations in the spring of 1960 included 

 determination of the number and kinds of fish 

 that passed upstream through the fishway to 

 areas above Little Falls Dam and of the size 

 of the sport fisheries for anadromous species 

 below the dam. 



To aid in the observation of the number 

 and kinds of fish using the fishway, an adjust- 

 able inclined screen was installed in the up- 

 stream exit channel. This structure forced 

 the fish to swim near the water surface where 

 they could be counted and identified. Observa- 

 tions were made from April 29 to June 15 

 (33 days), during 169 hours between 6:30 a.m. 

 and 8 p.m. No fish were seen using the fish- 

 way. Water temperature at the fishway exit 

 ranged from 11.6 to 23.3 C, dissolved 

 oxygen from 6.4 to 1.0 p. p.m. (parts per 

 nnillion), and pH from 6.8 to 7.6 



The attraction channel and waters imme- 

 diately below the dam were examined periodi- 

 cally for fish. Among the fish seen were carp, 

 Cyprinus carpio ; suckers, Moxostoma spp.; 

 channel catfish, Ictalurus punctatus ; crappies, 

 Pomoxis spp.; and sea lampreys, Petromyzon 

 marinus . Suckers and carp were observed 

 passing over the dam between the fishway and 

 the Maryland shore. 



When observations began at the fishway, 

 fishermen using drag hooks and dip nets were 

 catching large numbers of alewives, blueback 

 herring, and white perch immediately be- 

 low and above Chain Bridge, about 1 mile 

 downstream from Little Falls; they continued 

 to catch fish until mid- June. Several immature 

 striped bass were caught by hook and line 

 near Chain Bridge the first 2 weeks in May. 

 The first shad were caught by dip netters 

 in the lower rapids above Chain Bridge on 

 May 20, and about 200 were taken by mid- 

 June. No anadromous species were reported 

 caught upstream of the rapids about 0.8 mile 

 below the fishway. 



FISH PASSAGE, FISHWAY HYDRAULICS, 



AND UPSTREAM MOVEMENTS OF 



ANADROMOUS FISH, 1961 



Observations were made in the spring of 

 1961 to determine the nunnber and kinds of 

 fish that passed upstream through the fish- 

 way, the hydraulics of the fishway, and the 

 upstream limit of migration by anadromous 

 species. 



Fish Passage 



The experience gained by use of the inclined 

 adjustable screen to observe fish passage in 

 1960 led to the construction of a trap in the 

 fishway exit in the spring of 1961 (fig. 3). The 

 trap was installed so that only fish that had 

 passed up the fishway were trapped; thereby 

 the use of the fishway could be determined 

 exactly without an observer in attendance. 

 The trap consisted of a vertical baffle and 

 drop gate in the entrance channel, a re- 

 movable screen in the exit channel, and a false 

 bottonn lift attached to a hand-operated hoist 

 mounted on the fishway grating. 



Observations began May 3 and continued 

 to June 7. The trap was lifted 206 times 

 during these 36 days at various time intervals 

 between 7 a.m. and 8 p.m. No anadromous 

 species were seen in the attraction channel. 

 Resident species used the fishway under vari- 

 ous combinations of attraction flow. The fish 

 count through the trap was 10 suckers; 6 blue- 

 gills, Lepomis macrochirus ; 2 channel catfish; 

 and 5 carp (table 1). Minimum and maximum 

 water temperatures at the fishway exit during 

 the period were 12.7 and 23.3 C. Secchi 

 disk readings at 10 a.m. ranged from 10 to 

 41 inches. 



Fishway Hydraulics 



The fishway was operated at various com- 

 binations of attraction flow over a mean 

 daily river discharge of 6,540 to 33,600 c.f.s. 

 It was operated with 4 to 10 needle weirs 

 removed from the auxiliary water system 

 and with none to 3 stoplog openings closed 

 in the attraction chamber. Minimum and maxi- 

 mum drops in water elevation between pools 

 were 7.8 and 8.9 inches. Daily nneasurements 

 of water elevation within the facility indi- 

 cated that the fishway hydraulically oper- 

 ated as designed (table 2). 



Upstream Movement of Anadromous 

 Fish 



Observations began at the fishway on May 3. 

 At this time, connmercial fishermen were 

 catching shad at Gunston Hall, Va., about 

 2 5 miles downstream from Little Falls; the 

 fishery continued until late May. In May and 

 June large numbers of alewives, blueback 

 herring, and white perch were taken by dip 

 net and drag hooks near Chain Bridge and in 



