FISHWAYS. 



By H. VON BAYER. C. E., 

 Architect and Engineer, United States Bureau of Fisheries, 



GENERAL PRINCIPLES OF FISHWAY CONSTRUCTION. 



With the development in late years of water power for commercial enter- 

 prises on an economic basis, with the construction of canals for cheapening the 

 transportation of freight, with the proposition of irrigating the otherwise waste 

 lands of the country — all of which improvements call for the erectioir of dams 

 across our rivers — the steady decrease of fish life in the waters above said dams 

 or other obstructions has become more and more apparent, and the question 

 has presented itself how to enable the fish to ascend to the headwaters of rivers 

 in order to reach their spawning grounds for the propagation of their kind or 

 to follow their migratory habits in search of food as heretofore. This question 

 is being best met by the construction of suitable fishways. 



The underlying principle in the construction of fishways is the retardation 

 of the current velocity of a waterfall so as to enable fish to surmount it. Innu- 

 merable devices with that end in view have been invented and proved more 

 or less successful. Certain physical conditions in the location and a proper 

 method of construction are the important factors. 



Of the physical conditions, the two principal ones are (i) accessibility of the 

 fishway free from disturbance, its outlet being located in a pool at the bottom 

 of the falls where fish would naturally pass in ascending the river, and (2) an 

 abundant discharge of water through the outlet so as to attract the fish. It is 

 to be noted that fish as a rule do not ascend rivers at low-water stage, but 

 between mean and high water, and preferably during sunshine and_ warm 

 weather. 



In style of construction fishways may be classed in four systems: 



I. The inclined plane system, in which a series of baffle or deflecting plates 

 are so arranged in an inclined flume as to cause the water to follow in its descent 

 a long sinuous route. 



II. The pool and fall or step system, in which the water is brought down to 

 a lower level by a series of short falls with intervening pools. 



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