266 BULLETIN OP THE UNITED STATES FISH COMMISSION. 



or 74 per cent of the length; whereas at present they are to be found in only 4,107 miles, 

 a decrease of nearly 2,000 miles. This summary comprises only the principal rivers, 

 and if minor streams and tributaries were included, the total length from which shad 

 have been excluded would doubtless appear more than twice as great. In much of 

 that length sbad were quite numerous, the catch in many instances exceeding the yield 

 in the portion to which the fisheries are now confined. The upper section of the Pee 

 Dee is supposed to have yielded over 100,000 annually. In the James Kiver, according 

 to the late Colonel McDonald, the annual catch of shad in the 230 miles from which 

 they are now excluded "was at one time far in excess of the now (1880) entire catch 

 for the whole river." The present excluded length of the Susquehauna formerly 

 yielded several hundred thousand annually. In a report of the special commissioners 

 of Massachusetts appointed in 1865 to investigate the fisheries of that State, it was 

 estimated that at the beginning of the present century the annual shad yield in the 

 Merrimac River ranged from 500,000 to 1,000,000 in number, whereas none ascend 

 that river at present. 



The limitation in the range of shad in the rivers is the result of several agencies 

 in addition to the size of the stream, the most important of which are (1) natural falls, 

 (2) artificial dams, (3) pollution of water, (4) agricultural operations, and (5) extensive 

 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 the shad, among these being Great 

 Falls on the Potomac and Bellows Falls on the Connecticut, which form absolute 

 barriers to the further progress of shad that may reach these 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 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 Cape 

 Fear, the James, the Susquehanna, the Housatonic, the Connecticut, the Merrimac, 

 the Kennebec, and the Penobscot. The lengths from which shad are excluded appear 

 in Table A on page 270. 



Access to suitable spawning areas being a physiological necessity for the main- 

 tenance 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 sections is the immediate it is not the most 

 importanit effect of those obstructions. It has been the common experience in all the 

 shad rivers that whenever a high dam or other obstructidn 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 number 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 distance of the 

 obstruction from 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 oil' in 

 a definite coastal region the shad have almost entirely disappeared. 



This is clearly illustrated by the conditions on the Connecticut Eiver. The 

 erection of the Holyoke dam in 1849 prevented the fish from ascending above that 

 point and as they strayed about in the river below the obstruction they were taken in 

 greater abundance than formerly. At the Parsonage fishery near the mouth of the 



