106 American Fisheries Society 



1. Fishways of the older styles which have the advan- 

 tage of an inclined plane for the bottom have this either 

 vitiated by partitions producing steps or offset by the disad- 

 vantage of whirling currents and eddies. The Grand Lake 

 Stream fish way is faulty in both respects. 



2. All fishways having an intake at the top are open 

 to the further objection that flow of water through them 

 varies greatly at different levels or stages of the lake or 

 stream above the dam. And this variation is not limited 

 to the flow over the top, but, as the level varies, the rate of 

 flow through submerged openings, if any, varies also. 



An effort is sometimes made to obviate this difficulty by 

 completely enclosing the upper pool of the fishway so that 

 there is no overflow into it even at the highest stage of 

 water, but it is supplied through an opening submerged at all 

 times. This is good so far as it goes, since the variation 

 of level will be halved and in some situations halving will 

 keep it within the limits of the powers of the fish for which 

 it is intended. But it is clear that such an expedient would 

 not meet conditions like those at Grand Lake Stream, where 

 the fluctuations extend to the whole height of the dam. 



Thus far we seem to have wandered from the subject 

 announced at the start and to have been considering salmon 

 instead of small fry. But the fact to which attention has 

 been called as true of the ablest fish in the stream is still more 

 true of all the rest of its inhabitants. All prefer a foothold 

 and most of them absolutely require it. Moreover, all are 

 in a way and in some degree migratory and all are liable to 

 find themselves downstream of an obstruction. The migra- 

 tions of salmon, shad and alewives are determined by the 

 spawning instinct and by the search for food and suitable 

 temperatures. These motives affect all the creatures in the 

 stream more or less, so that it is doubtless true that differ- 

 ences in the migratory habits of fishes are of degree rather 

 than of kind. 



Nor can it be doubted that it is equally important to keep 

 the stream stocked with the smaller creatures as with the 



