was 6,000 bu, in 1960 it was 10,000 bu, and catch has remained essentially 

 stable since. In 1969 42 commercial shellfish licenses were issued, 1,344 

 resident licenses, and 856 non-resident. Total harvest was 23,875 bu of 

 quahogs . This is the most important commercial shellfish species in 

 Wellfleet Harbor. The 1969 commercial harvest of 10,500 bu was about 44% 

 of total harvest. (Abstracter's note: there is some confusion here. Table 

 24 gives commercial harvest as 22,900 bu, which, when the family harvest of 

 975 bu is added, comes to a total of 23,875 bu, but on the same page it is 

 stated that 1969 commercial harvest was estimated at 10,500 bu by the Town 

 Shellfish Constable. This figure is consistent with an earlier statement 

 that the harvest has been about stable since 1960.) Some areas had 

 concentrations of 7 to 8 quahogs/yd 2 , but average concentration was less 

 than 1 clam/yd 2 . Environmental conditions were favorable for quahog growth 

 and development. Ten-foot tides move large volumes of water over the beds, 

 providing sufficient food, oxygen, and waste removal. Salinity range was 

 20 to 34°/oo. Water temps exceeded 49°F from April through Oct, a 7-month 

 growing season. Water temps in low 70s in summer were adequate for 

 spawning. This is the most northern area to support a continuously active 

 quahog fishery. - J.L.M. 



418 



Currey, J. D. 1975. 



A comparison of the strength of echinoderm spines and mollusc shells. 

 J. Mar. Biol. Assn. U.K. 55(2): 419-424. 



In general mollusk shells were stronger than those of echinoids. 

 Meraenaria meraenaria shell had: dry specific gravity (s.g.) 2.80; 

 effective s.g. 1.77; 7 specimens tested; crushing strength 181.9 MN/m 2 , 

 standard error (s.e.) of mean 13.4; strength/s . g. 65.0; effective 

 strength/s .g. 102.8. Bone is 250 MN/m 2 , concrete 50 MN/m 2 , cast iron 

 800 MN/m 2 , and glass 1,000/m 2 . - J.L.M. 



419 



Currey, J. D., and J. D. Taylor. 1974. 



The mechanical behaviour of some molluscan hard tissues. J. Zool., 

 London 173(3): 395-406. 



Shells or other hard parts of several gastropod and bivalve species, 

 including Meraenaria meraenaria, 1 cephalopod, 1 insect, and 1 mammal, 

 were tested for tensile strength, modulus of elasticity in bending, and 

 modulus of rupture. Hard clam shells were fine crossed-lamellar to 

 homogeneous in structure with parallel orientation. M. meraenaria had 

 median values for tensile strength and modulus of rupture, and above 

 average for elasticity. - J.L.M. 



116 



