112 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Natural falls exist at the escarpment line in all of the rivers having 

 their sources above the coastal plane, but in only a few instances are 

 they of sufficient height to form insurmountable obstacles to the range 

 of shad, among these being Weldon Falls on the Roanoke River, Great 

 Falls on the Potomac, and Bellows Falls on the Connecticut, all of 

 which form absolute barriers to the further progress of shad that may 

 reach those points, excluding them from the whole of the river above. 

 Most of the other Atlantic coast streams having their sources above 

 the coastal plane have been made impassable at or a short distance 

 above the escarpment line by means of artificial dams for developing 

 water-power or for navigation improvements. In this class are the 

 Savannah, the Santee, the James, the Susquehanna, the Housatonic, the 

 Connecticut, the Merrimac, the Kennebec, and the Penobscot, the lengths 

 from which shad are excluded appearing in the aforegoiug table. 



Numerous attempts have been made by the erection of fishways 

 to enable shad to pass above these obstructions, among the costly 

 contrivances of this nature being those in the Savannah at Augusta, 

 the Santee at Columbia, the Potomac at Great Falls, the Susquehanna 

 at Clark's Ferry, the Housatonic at Birmingham, the Connecticut at 

 Holyoke, the Merrimac at Lawrence, and the Kennebec at Augusta. 

 And although these are modern constructions, designed by engineers 

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

 fish, 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 

 them, 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 they have passed 

 through breaks in the obstruction. 



Access to suitable spawning areas being necessary for the mainte- 

 nance of the fisheries if natural reproduction is depended on, and as 

 many of the spawning-grounds are located in the headwaters of the 

 rivers, it follows that while the exclusion of shad from the upper sec- 

 tions is the immediate it is not the most important effect of those 

 obstructions. It has been the common experience in all the shad rivers 

 that whenever a high dam or other obstruction has been erected across 

 the stream the fisheries above that point have at once ceased, and those 

 immediately below have for a year or two flourished on the large num- 

 ber whose ascent has been stopped by the barrier, and then they too 

 have declined. It also appears that the extent of this decrease below 

 the dam is largely dependent on the nearness of the obstruction to 

 the mouth of the river and the proportion of the spawning- grounds to 

 which they are denied access, and if all the breeding-grounds have 

 been cut off in a definite coastal region the shad have almost entirely 

 disappeared. 



This is clearly illustrated by the conditions in Connecticut River. 

 The erection of the Holyoke dam in 1849 prevented the fish from 



