batch at about 1 mm were 267.5 u at planting, 216,750 in a batch, size 

 1,219.5 y when moved outside, 42.5 days of growth, and 66.9% survival. Over 

 about 1 mm in size spat were held outside. Animals are sorted from time to 

 time to maintain individuals of about the same size together. Flow is about 

 1.2 1/min in a tray with base area 900 cm2 . The number of clams per tray is 

 related to size of animals, 2.5 mm or 0.005 g about 40,000 clams per tray, 

 10 mm or 3.5 g about 2,500 per tray. Growth at Conway starts about early 

 May and continues until the end of August. Clams 5 mm long at the beginning 

 of the growing season have reached about 30 mm at end of growing season. 

 Survival in the first two yrs was 70 to 90%. Clams grown in Menai Straits 

 and at Conway grew about the same, from a mean size of about 16 mm in January 

 1965, to about 45 mm in May 1967. Coverage was necessary to avoid predation. 

 Major problems were, mesh could be blocked by growth of weed and Ascidians, 

 or the frame could be covered by a layer of silt. These investigations have 

 demonstrated that larvae of Mereenaria mereenaria can be reared in substantial 

 numbers and spat can be cultured with only moderate losses. Satisfactory 

 growth and survival can be obtained in a number of places in England and 

 Wales. Expected growth and survival of 1,000,000 clams after 3 yrs are 20 

 to 34 mm and 80,000 animals. - J.L.M. 



1935 



Walne, P. R.,and G. J. Dean. 1972. 



Experiments on predation by the shore crab, Cavcinus maenas L. , on Mytilus 

 and Mereenaria. J. Cons. 34(2): 190-199. 



Unprotected plantings of hatchery-reared quahogs suffer heavy mortality. 

 Rates of destruction were measured in the laboratory by placing one crab each 

 in a series of boxes, each box containing 15 clams, 5 of each of 3 size 

 groups, held in running seawater. Numbers of clams eaten per unit time were 

 affected by a number of factors, illustrating the difficulty of measuring 

 predation rates in laboratory studies. Clams allowed to burrow in sand or 

 mud were less vulnerable than unprotected clams. A substrate of mud offered 

 better protection than sand. Competition may be important, as suggested by 

 one experiment in which 10 crabs in one container ate far more clams each 

 than 5 crabs in separate containers, although ratios of crabs to prey were 

 the same. By inference from more extensive experiments with mussels, other 

 things may be assumed for quahog : rate of predation is a function of water 

 temperature, crabs from some areas are more voracious than those from others, 

 numbers of prey of a certain size eaten by crabs was a measure of ease of 

 attack and not of size structure of clams available, crabs tend to select the 

 smaller prey, larger crabs can open larger bivalves, rates of consumption 

 varied from zero to more than 4 clams/day. Quahogs used in these experiments 

 varied in length from 2 to 26 mm, crabs from 15 to 79 mm in carapace width. 

 Highest rate of predation was by the smallest crabs on the smallest clams. 

 - J.L.M. 



1936 



Walsh, Dennis. 1974. 



The responses of the bivalve Mereenaria mereenaria to declining oxygen 

 tensions. Thesis presented to School of Marine Science, College of William 

 and Mary. 



Oxygen consumption, pumping rate, and filtration efficiency of Mereenaria 

 mereenaria were measured and compared at low and high oxygen tensions. Re- 

 sults indicated Mereenaria could maintain a constant O2 consumption in 

 declining oxygen tension, but critical oxygen tension (P c ) at which this 

 respiratory regulation ceased appeared to depend on the clam's size and sex. 

 Three modes of respiratory regulation were observed and described. The 

 efficiency with which the cilia of the gill were able to remove particles 

 was found to be independent of pumping rate, oxygen consumption and the 

 oxygen tensions. - M.C. (Confirmed by examination of original thesis. - 

 J.L.M.) 



540 



