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Fishery Bulletin 97(2), 1999 



10KV X17 1000U 001 06082 UM 



Figure 1 



Scanning electron microscopy (SEM) of the shell surface of a wild (A and 

 B) and cultured (C and D) juvenile softshell clam. Mya arenana (length 

 ca. 15 mm). The wild clam was sampled from a mudflat in Roque Bluffs, 

 Maine, in September 1992. The cultured clam was reared at the Beals 

 Island Regional Shellfish Hatchery and planted in May 1990, in a mudflat 

 at the mouth of the Chandler River, near the town of Jonesboro, Maine. 

 Photo B, taken near the umbo region of the wild clam, shows uninterrupted 

 concentric ridges and a lack of pits and amorphous grooves. Photo C is an 

 example of "the hatchery mark." It is a continuous, ca. 50-micron groove 

 that extends along the ventral slope (anterior to posterior) of both valves 

 and appears at that point on the shell surface associated with the time the 

 animal leaves the hatchery and is placed in the soft-bottom benthos. Photo D, 

 was taken along the anterior-posterior groove that appears at the interface 

 before the period when new shell is deposited once the individual is trans- 

 planted to the field. The white bar indicates a length of 1000 n for A and C and 

 100 \i for B and D. 



