268 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
proved ineffectual, and in 1880 a fourth passageway was placed iu the darn, 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 fishway 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 fishways are modern constructions, designed by 
engineers of ability, familiar with the principles of hydraulics and the habits of fisli, 
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 iu 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 laud 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 which 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 Oombahee, the Ashepoo, the 
Edisto, the Ohickahominy, the Mattaponi, and the Pamunkey, 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 
