17 



the process is repeated in another place. If the water forms 

 an eddy, the alewives swim in circles, apparently unable to 

 differentiate the back flow from that of the main stream, up 

 which they may show a reluctance to ascend. 



Alewives ascend in schools of five to ten, unless the run is 

 especially heavy, when a steady procession is formed. In 

 ascending falls some time is usually spent in manoeuvering for 

 the start. A quick dart forward directly into the current, with 

 a wriggling movement, shoots the fish rapidly along until the 

 first obstacle is reached, when it leaps into the air, returning 

 to the water once more for another short dash and a second 

 rise, if further obstructions are present. Thus, in passing a 

 series of abrupt rises in a natural stream, or in a straight-run 

 fishway, the alewife by a quick, powerful start makes a series 

 of rapid flights alternately through the air and water until it 

 reaches the calm water at the top. Many are unsuccessful, 

 and are swept downstream, where they begin the ascent once 

 more. In such locations a heavy run is a beautiful sight, with 

 the silvery white of the leaping fish projected against the darker 

 background of the stream. 



The exact height over which an alewife can leap is not known, 

 but it is probably in the neighborhood of 2 to 2| feet. The 

 1-foot rise used in our standard fishways is readily and easily 

 taken by the adults. The facilities afforded for a run, strength 

 of current and volume of flow determine the height which may 

 be surmounted. 



Exactly how much aid in passing over obstacles is furnished 

 by the serrated ventral scales is problematical. The fish fre- 

 quently turn slightly on one side and wriggle over obstacles, 

 especially in shallow water, clinging and even progressing 

 against tremendous odds. 



Descending Streams. — When leaving the spawning grounds 

 the adult fish pass through an interesting procedure. One 

 school of fifty fish was observed to swim in circles, gradually 

 approaching the opening to the stream. Suddenly, for no ap- 

 parent reason, they darted back into the deeper waters of the 

 pond, and, after repeating the advancing process, approached 

 a little nearer to the outlet. Again they made a sudden retreat 

 and a still nearer approach, and finally, after innumerable ap- 



