96 



THE SCALLOP FISHERY 



(5) Overcrowding. — Overcrowding tends to decrease the general 

 rate of growth, as too many mouths are drawing from a limited food 

 supply, and unless there is considerable circulation of water the amount 

 per capita is limited. The stronger the current the greater number can 

 be planted per square foot. The wire cages suspended from the raft 

 demoiLstrated the effects of overcrowding. Under uniform conditions 

 " seed " scallops averaging 21 per cubic foot gained 21.45 millimeters in 

 height, or 1,092 per cent, in volume, in seventy-six days, while those 

 averaging 153 per cubic foot gained 15.59 millimeters, or 659 per cent, 

 in volume, a difference of 433 per cent. In this case the circulation of 

 water was excellent, yet the difference was decidedly marked. 



(6) Cage v. Natural Growth for Small Scallops {"Seed ") . — The 1906 

 set on the raft was recorded by confining some in wire cages of small 

 mesh, increased in size as the scallops became larger, and by measure- 

 ments of the scallops which naturaEy were attached to the different spat 

 boxes. The result was that the caged scallops gained only 15.70 milli- 

 meters between August 17 and November 22 (ninety-seven days), both 

 classes being 3 millimeters in size on August 17, while the natural set 

 gained 29 millimeters in the same period. The difference is explained 

 by (1) lack of food, the meshes of the cage shutting off the circulation 

 of food organisms; (2) abnormal growth, due to deformities resulting 

 from cage environment. It is impossible to overcome these difficulties 

 in obtaining the rate of growth of the scallop from caged specimens. 



