270 



BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Access to suitable spawning-grounds in sufficient numbers to compensate for loss 

 by capture and natural causes is a physiological necessity for the maintenance of the 

 fisheries if dependence is placed on natural reproduction. But from the foregoing it 

 appears that the construction of dams has excluded shad from a large portion of the 

 spawning-grounds, notwithstanding the erection of fishways in those obstructions; 

 sawdust, chemicals and other refuse and agricultural operations have greatly impaired 

 the utility of the spawning areas even now available, and the extensive fisheries have 

 very largely decreased the number of the shad reaching those areas. These adverse 

 agencies have reduced natural reproduction to almost an insignificant factor in the 

 maintenance of the present fisheries and have rendered artificial propagation essen- 

 tial to their prosperity. During the seventies the returns of the fisheries reached a 

 minimum ; then the results of artificial propagation began to appear, not only restor- 

 ing the former abundance of shad, but even increasing the catch. 



The total shad yield on the Atlantic coast and rivers in 1880 numbered 5,162,315; 

 in 1888 it was increased to 10,181,605; in 1896 it was further increased to 13,067,469, 

 29 per cent greater than in 1888 and nearly three times as great as in 1880. While 

 this increased yield was preceded by an increase in the quantity of apparatus used, 

 yet it was made possible by the greater abundance of shad, due to artificial propaga- 

 tion. Comparing 1880 with 1896, it is observed that the increase in the yield numbered 

 7,905,154. At 20 cents each, which is the average price paid by consumers, this rep- 

 resents an increase of $1,581,030 in the value, over 50 times the expenditures for shad 

 propagation ; a result probably unsurpassed in any other line of public appropriation. 

 The large number of persons employed in this fishery and the present inability of 

 natural reproduction to maintain the supply make it essential that no decrease be made 

 in this important branch of fish-culture. 



A. Summary of the original and of the present limit of shad range in twenty-three of the principal 



rivers of the Atlantic seaboard. 



