tide. Because they can exist on almost every kind of bottom and over a wide 

 depth range, possibilities for clam farming are promising. Nearly all 

 develop as males, but, usually during the 2nd yr, about half change to female. 

 Some may spawn at 3 or 4 months, but most hard clams spawn at 1 yr. Spawning 

 begins when water temp reaches about 7 3°F. Spawning season is longer in 

 southern waters. Several million eggs, 1/325 inch in diam, can be discharged 

 by a female in one season. Setting takes place in 10 to 14 days, depending on 

 temp. At 1/8 to 1/4 inch young clams burrow into the bottom; they can crawl, 

 but are essentially stationary. Growth is affected by currents, depth, 

 salinity, and temp. Good currents are needed to provide food and oxygen and 

 to keep beds clean. Natural beds are in brackish water of salinity 10 to 

 28°/oo. in the intertidal zone clams do not feed when exposed, and growth is 

 retarded. Most clams become inactive when water temp falls to 42°F and remain 

 inactive until spring. Thus, in northern waters clams grow only from May to 

 mid-Nov. Growth is fastest from mid-July through Sept. Growth varies with 

 locality. In New England average size at end of first growing season usually 

 is less than 1/4 in. Size increases to about 1.1, 2.0, 2.5, 3.0, and 3.2 in 

 at ages 1 1/2 to 5 1/2 yrs respectively. The few clams which reach 5 1/2 

 inches are 20 to 25 yrs old. Principal enemies are Neverita duplicate* and 

 Poliniees heros, which perforate the shell in the umbo region, and Fulgur 

 caniculatus and F. cariaa which break the edges of the clam shell and insert 

 the probiscis to feed on the meat. Sea stars attack and devour clams lying 

 on the bottom, but are not dangerous to clams in their burrows. Waterfowl 

 and some bottom-feeding fishes also are predators. At present the supply of 

 hard clams exceeds demand. Cultural methods could be used to increase the 

 supply. A hard-clam farm could yield up to 600 bu of 2 1/2-inch clams per 

 acre per yr. Chief requirements are good water circulation and sufficiently 

 firm bottom. At least 3 ft of water at low tide is best, to avoid effects of 

 severe winters. Water should be clean and well protected from wind and rough 

 water. A nearby source of seed clams is important. Hard clams usually set 

 less abundantly than soft clams. Seed should not be planted in cold weather 

 because they will not burrow. Bottom should be cleaned of debris and 

 predators. In good water circulation as many as 25 seed clams/ft^ of bottom 

 can be planted. The edible portion makes up about 16 to 19% of the total 

 weight. About 12 pints of meats can be obtained from a bushel. - J.L.M. 



1112 



Loosanoff, "Victor L. 1950. 



Variations in Long Island Sound oyster set. Atl. Fisherman, Jan. 1950, 30: 

 15, 47. 



(Identified by a footnote as excerpts from a paper by Dr. Loosanoff.) Good 

 sets of oysters in Connecticut are infrequent. It is concluded that absence 

 of proper' food may be the cause. This is supported by the observation that 

 if predation were the cause, larvae of clams (not identified, but almost 

 certainly Mercenaria (Venus) mercenaria) and other mollusks would have 

 suffered a similar fate, which they do not. In the laboratory, oyster larvae 

 apparently could not assimilate certain plankton forms, and did not grow, 

 although the same foods were readily assimilated by clams. This was true 

 even if oyster larvae were the dominant mollusk in cultures. In the field, 

 clam larvae of all stages are almost always present during summer, but oyster 

 larvae seem to disappear within a few days of hatching. - J.L.M. 



1113 



Loosanoff, V. L. 1954. 



New advances in the study of bivalve larvae. Am. Scient. 42(4): 607-624. 



The work had 5 principal objectives: to open up a field for studies of 

 physiological and ecological requirements; interest in heredity and selective 

 breeding; identification of mollusk larvae in plankton collections; study of 

 larval diseases and parasites and their control; and preliminary steps toward 

 producing commercial supplies through artificial propagation. Methods of 

 spawning, food requirements, effects of temp and other environmental factors, 

 and larval diseases and parasites are discussed. Data are given for hard clam 

 (Mercenaria mercenaria) and other molluscan species. - J.L.M. 



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