IV -A NEW SYSTEM OF FISHW AY-BUILDING. 



By Marshall McDonald. 



1. The object of pishways. 



It is a well esttiblislied fact that the river fisheries of the Atlautie 

 States have steadily decreased both in value and annual ijroduction for 

 many years past. In some instances species that were at one time 

 common in certain of our rivers are no longer taken. Indeed, the an- 

 nual run of those lish which still continue their migration to the rivers 

 has undergone alarming decrease ; and in many cases become too in- 

 significant to furnish the motive or material for organized fisheries. 



Several causes, probably, liave concurred in producing this decrease: 

 (1.) The capture of the greater portion of the run each year may not 

 have left sufficient to maintain production under natural conditions. 

 (2.) The erection of dams or other obstructions in the rivers has, in some 

 cases, absolutely excluded certain species from their spawning grounds; 

 the result being eventually to exterminate the species referred to in 

 those rivers. In all cases the existence of such obstructions has deter- 

 mined a decrease in the natural productiveness of the stream pro tanio 

 with the diminution of the breeding and feeding area. 



The remedy for the condition of things above indicated is to be found : 

 (1.) In the enactment of such legislation as will control excessive fish- 

 ing, and prohibit destructive methods. (2.) In compensatiug for the 

 insufficient natural supply by artificial propagation and planting. (3.) 

 In extending the area for breeding and feeding by overcoming natural 

 obstructions by means of fishways. 



If the anadromous fishes only entered our rivers for the i)urpose of 

 spawning, and their progeny spent no part of their life in our fresh 

 waters, then the increase which we could determine by artificial propa- 

 gation would be practically without limit. The fish-culturist, in order to 

 maintain the supply, would only have to produce the joung fry in num- 

 bers sufficient to replace losses by capture or by casualty. As regards^ 

 all the anadromous species, however, which are the object of commer- 

 cial fisheries, viz, the salmon family, the shad, the herring or alewife, &c., 

 it is necessarj^ that the young, after hatching, should remain for some 

 time in our fresh waters, feeding and growing, and, of course, finding 

 the necessary food in these waters. The extent of the breeding and 

 feeding area of any river basin is, therefore, necessarily the measure of 

 its possible productiveness. A given area, when ijressed to its maxi- 

 mum of production, cannot provide for more than a given number of in- 

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