180 MARINE FISHERIES OF NORTH CAROLINA 



centimeters in length can dig to depths of five or six inches. During these 

 stages they frequently wander short distances on the surface. Once an 

 adult clam buries itself, it rarely comes out on the surface again. The 

 anterior end containing the mouth is buried deepest while the posterior end 

 is upward, the siphons extending to the surface through which the clams 

 gather in their food and exchange water. 



ECOLOGY 



TYPE OF BOTTOM. Soft clams grow best in a bottom composed of a firm 

 mixture of mud and sand in which they burrow with some ease. Loosanoff 

 (1943) considers a mixture of fine sand and mud in a ratio of two parts 

 of sand to one part of mud as the most desirable type of soil. The con^- 

 sistency of the bottom should be firm enough to prevent ready shifting. 

 Clam flats are sometimes composed of various types of bottom from sand or 

 hard clay to rocky or gravel beaches. The young clams often work their 

 way down between roots of grass or other vegetation making it difficult to 

 dig them out. 



SALINITY. The soft clam can endure salinities ranging from brackish to 

 salt water. It is found growing in waters of a salinity as low as six to eight 

 parts to as high as twenty-eight parts of salt per thousand. Adult clams can 

 apparently be transferred from one extreme to the other without detriment. 



RATE OF GROWTH. A marketable clam of more than two and one-half 

 inches can be produced in two years in the New England region. Shell 

 growth may occur throughout the year in some localities, but in New 

 England the most rapid growth is during the summer months. The age 

 limit of soft clams is estimated to be ten to twelve years (Loosanoff, 1943). 



SOFT-SHELL CLAM CULTURE 



These clams are hardy and lend themselves to cultivation which has been 

 successfully carried on to a limited extent in New England. Unproductive, 

 barren areas can be restored or replenished with small clams. Circulation 

 of water is essential for a supply of oxygen, and a good current is necessary 

 for rapid growth. A knowledge of the clam's life history and microscopical 

 examinations of the water aid in getting the suitable materials overboard 

 at the proper time to allow clams to attach. After a set of clams has been 

 secured, it is necessary to move them before they begin to burrow. The 

 natural set is usually sufficient to supply seed. These are gathered by sifting 

 the clams out of the sand, digging shallow trenches into which the tide will 

 wash them or by transporting both soil and clams from areas with thick sets. 

 The bottom should be cleared of weeds and softened by raking to allow 

 the clams to burrow more easily. About two hundred and fifty bushels of 



