44 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



The Rock-Crab.— Anyone who frequents the shore, and has ever 

 watched the incoming- tide, knows that the rock-crabs, are seen in 

 -rout numbers following the encroachment of the water, eager to 

 take possession of the new territory. This is especially noticeable 

 on the evening tide. These crabs, as may be readily observed, are 

 enormous feeders, and evince a shreAvdness in overcoming difficul- 

 ties and taking advantage of situations which is quite remarkable. 

 To just what extent they may be detrimental to the clams is not 

 known. In all probability they help destroy the young clams 

 which are just setting, and a clam which is unfortunate enough to 

 push its way out of the soil would be made short work of. In the 

 early part of September an incident was noticed which showed the 

 possibilities in a crab. A rather small-sized crab, about 1^ inches 

 across, was seen to attack and eat a large scallop, measuring about 

 2£ inches across the shell. The crab approached the scallop and 

 warily touched it with one claw. The scallop immediately closed 

 up. The crab quietly waited till it opened, and then quickly 

 thrust its claw into the opening between the shells. The scallop 

 closed over the claw, but the crab did not appear to be concerned 

 about it. When the scallop again opened, the crab turned its 

 claw so that the opening would be kept as wide as possible, and 

 then proceeded to tear ont the rim and viscera and eat them at 

 its leisure. 



Because of this observation, an experiment was made to 

 show whether the crabs could be induced to dig up large clams. 

 A large box (\\ feet x 4 inches across the top and \h feet deep) 

 was filled with sand, and fifty clams, averaging l£ inches, were 

 buried just below the surface. Four large rock-crabs were put in, 

 and the top covered with wire screen. The box was then set out 

 just above low-tide mark, and being opened, two weeks later, the 

 surface was found to be covered with shells. Upon screening the 

 sand, only twenty-nine clams were found alive. The bare shells, 

 with broken edges, bore witness to the fate of the other clams. It 

 is not to be concluded from this that under normal circumstances 



