ENVIRONMENT AND GROWTH OF THE SOFT CLAM 



285 



recovery, however, the initial length, based on 

 measurement of the check-mark on the shells 

 caused by the transplanting, varied among test 

 areas. In each case, the clams recovered from 

 plantings at Robinhood Cove had a greater initial 

 lengtli tlian those from corresponding groups in 

 the other test areas. It is likely that the smaller 

 clams planted at Robinhood Cove were eaten by 

 green crabs (these smaller clams were nearer the 

 surface of the flats), which resulted in a greater 

 initial length of clams recovered in this area. 



GROWTH 



Mean growth shown in table 1 is based on the 

 difference between total length and initial, or 

 "planted," length of each clam as determined at 

 the time of recovery. Monthly samples taken 

 during the winter of 1951-52 were combined to 

 provide an adequate sample for statistical analysis. 

 Combining these samples was justified by the fact 

 that there is virtually no growth during this period, 

 as shown by figures 4 and 5. 



The mean growth rates of test clams ranged 

 from 2.26 mm. for a group at Falls Cove to 20.30 

 mm. for a group at Sagadahoc Bay. Table 1 and 

 figures 4 and 5 show that there is a tendency for 

 growth rates to vary less within each test area 

 than between test areas. At Bedroom Cove the 

 native clams grew only 3.55 mm., but clams trans- 

 planted from three other origins also grew slowly. 

 At Sagadahoc Bay the clams from the same origins 

 as those planted at Bedroom Cove grew several 

 times as much. At Robinhood Cove all groups 

 grew much faster than did those at Bedroom Cove. 

 Native clams at Falls Cove averaged only 2.85 

 mm. growth, and those transplanted from Meet- 

 inghouse Cove and Western Beach also grew very 

 slowly. Contrast this with Plum Island Sound, 

 where clams from Meetinghouse Cove and Western 

 Beach grew more than 19 mm. 



Statistical analyses (described in appendix B) 

 show that the differences in mean growth between 

 test areas are highly significant. It is safe to 

 conclude that clams from a common origin adopt 



CENTER SAGADAHOC BAY 



BEDROOM COVE 



FinuKE 4. — Growth curves for groups of dams planted in Sagadahoc Bay and in Bedroom Cove, .smoothed by moving 

 averages of three. Origin of clams was as follows: 1, Western Beach; 2, Meetinghouse Cove; 3, Sagadahoc Bay; 4. 

 Bedroom Cove. 



