ENVIRONMENT AND GROWTH OF THE SOFT CLAM 



281 



80 



2 60 



40 



I 

 t- 

 o 



20 



CENTER 

 SAGADAHOC BAY 



12 3 4 5 6 



AGE IN YEARS 



FiGORE 2. — Comparat ive growth rates of soft clams from center of Sagadahoc Bay and from Bedroom Cove. 



ami that <!;rovvtli is accelerated where currents are 

 swift. Belding (1930) reported that the most im- 

 portant factor in clam growth is a good current, in 

 its role as a food carrier, oxygen bearer, lime fur- 

 nisher, and sanitary agent. Newcombe (1935) 

 showed tliat seasonal growtli rates for clams during 

 the same year and during different years corre- 

 spond with abundance of diatoms and not with 



temperature. He also stated that excess surface 

 silt on the beach limits the growth rate and 

 survival of Mya arenaria. 



Each of the authors cited attributes variations 

 in growth t&\jc to one or more environmental 

 factors. Tlie possibility that growth variations are 

 indications of hereditary racial differences needed 

 to be explored. 



DESIGN OF EXPERIMENT 



The experiment was based on tiie hypothesis 

 that if growth variations are due to hereditary 

 factors, transplanted clams should maintain the 

 growtli rate they had in their native habitat, 

 whereas if eiiviroimieiit is the cause of growtli 

 variations, transplanted clams should assume the 

 growth cliiiracteristics of native clams in tiic new 

 area. Clams were transplanted into various areas, 

 and the growth rates were measured in terms of 

 increase in shell length during the experimental 

 period of 1 year. 



Experimental areas were eslablislied in Bedroom 



Cove and in the center of Sagadahoc Bay (fig. 1). 

 In each area we planted native clams and clams 

 from the other area. For a further comparison we 

 planted in each area clams from two other flats, 

 Western Beach and Meetinghouse Cove (fig. 3). 

 Western Beach is a sandy flat at the mouth of the 

 Scarboro River where seed clams are abundant ; the 

 growth rate of clams at Western Beacli is inter- 

 mediate between that in Sagadahoc Bay and that 

 in Bedroom Cove. M(>etingli()use Cove is a silty 

 area in the Medoniak River system; seed clams are 

 extremely abundant there and the growth rate is 

 low, but better than in Bedroom Cove. 



