594 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



below whicli, in favorable seasons, some Inindreds of salmon are caught 

 one is so rarely seen to leap, tbat I have never heard of an instance, and 

 for a salmon to surmount it by swimming up the sheet that falls over it 

 can hardly be thought possible. 



Salmon move both by night and by day. It is generally assumed by 

 European authorities that they will pass dams more readily by night 

 than by day. It is the opinion of the Penobscot fishermen, however, 

 that they rarely, if ever, attempt the passage of difficult places by night. 

 In support of their opinion, they state that at Ayer's Falls, when it was 

 customary to fish on the dam and in the passage-way now set apart for 

 a fish-way with dip nets, no salmon could be caught during the night; 

 the drift-nets plied on the shallow rapids a short distance below being 

 meanwhile quite successful. At daylight, however, fortune deserted 

 the drift-nets, and from that time till the day was well advanced it 

 rested with the dip-nets on the falls. 



The shad, superior "to the alewife in size and strength, is far inferior 

 in courage. Timidity is one of its prominent charactedstics. It is said 

 to be frightened by the shadow of a bridge across its path. In a broad 

 current it sometimes surmounts impetuous rapids, but I have never 

 heard of its ascending a perpendicular fall, and it rarely ventures to fol- 

 low up a small side-current, such as would suffice for the passage of 

 salmon and alewives. So little success has attended the efforts to induce 

 shad to ascend fish-ways, that in discussing most of the devices noticed 

 in this pai)er they will be almost entirely left out of the account. 



C— THE COKSTEUCTION AND LOCATION OF FISH- WAYS. 



In the planning of a fish- way, there are several important things to be 

 considered. The fish demand that it be accessible, attractive, and easy 

 of ascent. The parties at whose expense it is built demand that it be 

 durable and reasonably cheap. The owners of the water-power demand 

 that it be not wasteful of water. To meet these various desiderata 

 requires a careful consideration of the questions of location, capacity — 

 form, material, and mode of construction. For our present purpose, 

 however, it will be sufficient to discuss briefly the questions of accessi- 

 bility, attractiveness, and ease of ascent, and then notice the principal 

 devices by which it has been sought to attain them. 



1. — SITUATION. 



Accessibility may be set down as the first essential quality. To secure 

 t, the foot of a fish way must be so located that the fish will readily 

 find it. Now, as has been before remarked, salmon, shad, and alewives 

 all follow the main current of the river until they meet some obstruction 

 sufficiently formidable to check their progress ; at the base of this they 

 swim many times back and forth, extending the search at each turn 

 but a short distance down the shore on either hand. If there be no 

 convenient pool at the base of the fall, they drop back occasionally to 



