50 



upon alewife streams, unless opened regularly during the spring, 

 should be equipped. At the present time too few dams are 

 equipped with adequate fishways. 



Cranberry Bogs. — A water supply is essential for the suc- 

 cessful operation of the cranberry industry, and in southern 

 Massachusetts numerous bogs are found along the alewife 

 streams. Cranberry bogs are designated as dry or wet. In the 

 former the water is pumped from a pond or reservoir upon the 

 bog, where it is held until released to drain back into the pond. 

 In the latter the bog is flooded by damming the stream which 

 runs through it (Fig. 5). Little damage results from the dry 

 bog, except for an infinitesimal amount of chemical pollution 

 from spraying, the lowering of the water level in the pond, and, 

 where the intake is not screened, the destruction of a few small 

 fish. The wet bog, however, has become a serious menace to 

 the alewife fishery, causing either partial or complete ruin in 

 certain fisheries, e.g., Marston's Mills Herring River. The 

 interests of the fishery and the cranberry industry are diametri- 

 cally opposed. In the welfare of the latter the course of the 

 natural stream is changed, channels made, water diverted by 

 ditching, and dams erected for reservoirs or for flooding the 

 bogs. Properly regulated, these changes could be accom- 

 plished without material damage to the fishery, but improp- 

 erly controlled they have resulted in serious effects. The 

 cranberry industry affects the alewife fishery in the following 

 ways : — 



(1) The small dams are usually not equipped with fishways, 

 and the owners are supposed to raise the sluiceboards during the 

 annual run. However, at certain times the owners may find it 

 expedient for the welfare of the bogs to have the water remain 

 for a longer period, thus blocking or retarding the progress of 

 the fish, although ordinarily there is little need of water over 

 the bogs at the time of the spring run. 



(2) The course of the stream occasionally is changed by 

 ditches and canals, which are inferior to the natural channels. 



(3) The young alewives descending to salt water are some- 

 times stranded by the temporary flooding of the bogs during 

 the early fall, a condition which may be avoided by the use of 

 screens or by careful flooding of the bogs. 



