264 Roosevelt Wild Life Bulletin 



only change of locality. Fish are enabled to ascend farther up some 

 brooks and even onto overflowed areas, but since in many instances, 

 the stored waters are sooner or later drawn upon, the possible effects 

 are manifestly serious. A sudden drawing off of the water may not 

 only let out many fish which have congregated above dams, but also 

 seriously affect those which have entered the overflowed tracts and 

 small brooks, often leaving them stranded or to slowly perish as the 

 pools left by the receding water become heated or evaporated. High 

 water of a lake may facilitate the ascent of tributary streams by 

 some species in the breeding season, but it also covers former shoals 

 with excess of water, so that other places of suitable character must 

 be sought, and these may not exist. 



If, by chance, fish have become accustomed to temporarily pre- 

 vailing conditions, sudden changes can only be to their general dis- 

 advantage and must necessarily react unfavorably upon the 

 perpetuation of the fish supply. 



Dams also interfere with the dispersal of fish as well as with their 

 migrations, by obstructing the passage from one body of water to 

 another or from one section of a stream to another. As has been 

 stated, some species make seasonal movements from one place to an- 

 other for breeding, feeding, or to meet changing seasonal conditions. 

 These obstructions usually are to movements in one direction only. 

 They often permit a downstream movement but not a return (figures 

 36, Z7)- So fish which inhabit a lake or the lower sections of a 

 stream must be very seriously affected. In some cases this may be 

 an advantage, by preventing the invasion of upper waters by un- 

 desirable fish. 



Depletion of many waters and inability to restock them with cer- 

 tain species may be attributable to dams. In some localities attempts 

 have been made to remedy such conditions by affording a passage past 

 or through the dams by means of a structure commonly known as a 

 " fishway." 



Fishways. The construction of fishways for anadromous fishes 

 was one of the earliest measures directed toward conservation 

 adopted by state governments. Laws were enacted requiring the 

 owners of dams to provide fishways and in many instances the fish- 

 ways were constructed and maintained for awhile to become neglected 

 in later years, and seldom have new ones been made. The law con- 

 cerning the structures was seldom enforced. One reason for the 

 neglect was that the fishways appeared to do no good. The fish did 

 not ascend them. 



Thirty years ago an article appeared in a sportsman's journal 

 (Waters, '91) in which, among other things, it was stated that 

 there was an expensive fishway at Holyoke, Mass., built some years 

 previously at a cost of $30,000 and so far as known no shad, sal- 

 mon, or blackbass ever got to the top of the stairs. Nothing but 

 eels ascended it. The facts are that many fishways have been faulty 

 in their structure or location. Furthermore, the same type of fish- 

 way will not answer for all kinds of fish, and fishways are expensive 

 and difficult to make effective. 



