268 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



proved ineffectual, and in 1880 a fourth passageway was placed iu the dam, this one 

 consisting simply of an opening 125 feet wide, this plan being chosen because it 

 conformed to a natural break, experience having shown that shad passed through 

 such an opening more readily than through any regular fish way that had been 

 constructed. But it is only in very low and little-used dams that such breaks can 

 be made without injury to the original purpose. 



Although the above-described fish ways are modern constructions, designed by 

 engineers of ability, familiar with the principles of hydraulics and the habits of fish, 

 yet none of them appears to be successful for shad, this fish being so timid that 

 it will not enter fishways readily used by salmon, alewives, and other species. True, 

 a few individuals may pass through some of the fishways, but the number is not 

 sufficiently large to be of any practical value, and in a majority of instances where 

 shad are reported above a dam they have swum over the crest during freshets or 

 have passed through breaks in the obstruction. 



The utility of the spawning areas below the dams has also been impaired by 

 chemical, sawdust, and other refuse from mills and towns on the river banks. In a 

 number of small streams these have almost completely destroyed the spawning and 

 feeding areas, but regulations against this practice now exist in most States. 



Increased agricultural operations have also had some effect on limiting the range 

 of shad up the rivers. At the time of the settlement of the river valleys most of 

 those areas were covered with forests and the ground was carpeted with leaves and 

 moss, which checked the surface flow of water and restricted its evaporation, thus 

 tending to constancy in the flow of rivers; and freshets were rare and of insignificant 

 proportions. With increase of population the forests were cleared away and large 

 areas of land brought under cultivation, causing injurious meteorological changes and 

 more numerous and destructive floods. During heavy rains the plowed soil upon the 

 hillsides is easily washed into gullies, through whicli the water is quickly conveyed to 

 the rivers, filling them beyond their capacity and bringing into them masses of earth 

 and other debris, thus covering the spawning-grounds. The freshets are soon over, 

 and the flow of water in the streams becomes so small that shad are not induced to 

 proceed so far up as formerly. 



On some of the southern streams decreased navigation has resulted in reducing 

 the length of shad range. This is especially true of the Combahee, the Ashepoo, the 

 Edisto, the Chickahominy, the Mattaponi, and the Pamuukey, the channels of which 

 are now much encumbered with drifting logs, overhanging trees, brushwood, and shoals 

 of loose, shifting sand, through which a passageway for the ascent of fish was formerly 

 maintained by navigation and the rafting of timber. 



The most important factor in reducing the inland range is the extensive fisheries 

 near the coast. In the first half of the present century shad were caught all along 

 the river course, every point yielding its quota for local use and the limited demand 

 not warranting the prosecution of the fisheries so vigorously as to cut off the "run" 

 at points above. But the profits derived from shipping shad to populous centers 

 resulted in a concentration of the fisheries at points near the mouths of the rivers 

 where most convenient shipping facilities exist, resulting in certain narrow streams in 

 practically excluding shad from the middle and upper sections where the spawning- 

 grounds are located. The effect is not so apparent as in the case of impassable 



