for navigation purposes. The Ohio River receives the flow from 19 major 

 tributaries and over 100 reservoirs, in addition to discharges from about 

 295 municipalities and 200 industries. Although the flow in the Ohio River 

 is quite variable, it is highly regulated by the U.S. Corps of Engineers 

 through their manipulation of the reservoir and dam system (see map). 



The change in river regime caused by its canalization and increased 

 pollution load has altered the species composition and relative abundance 

 of biological organisms from those found and recorded by the early white 

 settlers, and changes in dam construction have had an impact upon migratory 

 patterns of fish. The old wicket dams, for instance, permitted open-river 

 conditions for many months of the year, and fish were free to travel from 

 one pool to another. The installation of the fixed structure high-level 

 dams across the river does allow fish to travel from one pool to another, 

 although this does not occur in the same free manner as before. In addi- 

 tion, the change in variety of food organisms has been substantial and was 

 probably more influential ecologically than any changes in water quality. 

 These alterations must be taken into account when evaluating the results of 

 the lock-chamber studies. For example, the shift from a free-flowing 

 stream with a significant slope to a canalized river separated by a series 

 of low-level locks and dams and then to the present condition of longer, 

 deeper pools separated by fixed structured dams has significantly modified 

 biological habitats to the extent that many previously abundant species 

 such as the sturgeon and the paddle-fish are now reduced in number and 

 their distribution limited. Some species of fish (such as the deep-bodied 

 suckers, the gizzard shad, and perhaps some of the smaller sunfish) have 

 increased in abundance, for the lakes created by the dams favor them. 

 Carp, another species introduced into the Ohio, shows strong preference for 

 the quiet waters furnished by the dams. 



From the standpoint of spawning and reproduction of fish, the Ohio ex- 

 hibits many of the traits of a large canalized river. The stream is 

 characterized by a gravelly bottom, a paucity of shallow water and yery 

 few, if any, riffles or weeds suitable for nesting. Shore lines in many 

 localities show the effects of bank erosion caused by the large variations 

 in river flow and to a lesser degree the backwash of commercial and recrea- 

 tional boats navigating the river. As a result, the number of areas suit- 

 able for spawning takes place in small creeks and tributaries. Sampling 

 performed during the course of the ALRP, however, revealed that a large 

 number of species requiring shallow water, weeds, and riffles to reproduce 

 were in fact spawning in the small tributaries and then returning to the 

 main stem. The sauger, round-bodied suckers (red horses), largemouth and 

 smallmouth bass, and golden shiners prefer the small tributaries with 

 shallow gravel bars and weeds for spawning, but they are found throughout 

 the Ohio as both finger lings and mature fish. 



CHEMICAL FISHING 



Various chemicals (rotenone, toxaphene, creosol, copper sulfate, and 

 sodium cyanide) have been used in fish sampling. The most acceptable of 



162 



