between the valves which kills the clam there is no evidence to support 

 this. Penetration and consumption of the clam is purely mechanical. The 

 soft parts are consumed by rasping and swallowing. In the laboratory 6 

 conchs opened and consumed 17 Venus meroenaria in 23 days as well as 69 

 mussels, 3 soft clams, and one razor clam. Quahogs were 2-5 cm long. In 

 another laboratory experiment consumption of quahogs 2 to 7.5 cm long 

 buried in sand was nearly 1 clam per week. In an experimental site in 

 Little Egg Harbor, N.J. conchs were present at a density of 1 per 100 ft2. 

 In a 47-day experiment, in which caged bivalves of various species were 

 exposed to oyster drills, moon snails and conchs, quahogs were penetrated 

 only in the absence of thinner shelled prey. Oyster drills and moon snails 

 grew much faster when they fed on mixed bivalves than on hard clam alone. 

 In the field Busyoon consumed 0.35 hard clams per week in summer, in aquaria 

 0.86 clams per week in winter. In the field Poliniaes consumed 0.15 hard 

 clams per week in summer. The higher rate in aquaria is explained by the 

 absence of alternate foods. Field experiments showed that 91 conchs (the 

 density found on a 75 by 125 ft area of bottom) could consume 700 quahogs 

 from May through September. Although conchs and other predators prefer 

 other prey, conch is the most serious enemy of large quahogs. In field 

 experiments a small blue crab entered a cage of Busyoon and mixed bivalves, 

 molted, and could not escape. It opened and consumed 4 quahogs. This and 

 other unpublished cage studies confirm the damage that can be done to hard 

 clam and other bivalves by blue crabs. In one experiment a 12 cm caged 

 blue crab consumed 6 quahogs 3 to 4 cm long in a week. Each predator leaves 

 its signature on the empty valves. Photographs are included to show the 

 relatively straight-sided hole made by Urosalpinx , sharply beveled hole of 

 Polinioes , smooth chipping by Busyoon , and jagged chipping by Callinectes . 

 Blue crab is probably a more serious enemy of hard clams than Busyoon. 

 (Abstracter's note: probably the most serious enemy of adult quahogs.) - J.L. 



274 



Carriker, M. R. 1951. 



Ecological observations on the distribution of oyster larvae in New Jersey 

 estuaries. Ecol. Monogr. 21: 19-38. 



Bottoms of estuaries along the Atlantic coast of N.J., especially in the 

 southern 2/3 of the State, where estuarine development is extensive, are 

 inhabited by Crassostrea virginioa and Venus meroenaria. In warmer parts 

 of the year bivalve larvae dominate the plankton and identification is 

 difficult. Biologists in N.J. are certain that they can identify larvae 

 of Mercenaria and 7 other species. - J.L.M. and M.W.S. 



275 



Carriker, M. R. 1952. 



Some recent investigations on native bivalve larvae in New Jersey estuaries. 

 Proc. Natl. Shellf. Assn. (1950): 69-74. 



Studies were carried out in Little Egg Har. , N. J. , the last 3 summers. The 

 Harbor is 4 mi wide, 10 mi long with average depth at mean low water 4-7 ft 

 in the largest part, only one prime inlet, and a deep, narrow channel. 

 Tidal range in spring is about 3 ft. Salinity is usually uniform in the 

 entire southern 2/3 and changes during the tidal cycle only about 17" 

 except near the negligible influence of small tidal creeks. Temp also is 

 relatively uniform. Current velocities are 130 cm/sec in the inlet, about 

 12 cm/sec in the middle. A large concentration of hard clams in the 

 southeast portion of the Harbor was sampled at least from 10 June to 4 Sept. 

 At straight-hinge stage larvae were approximately 1 day old. They grew from 

 about 98 u to 200 u in about 7 days, but with considerable variation, 

 reaching setting stage in 5 to more than 10 days. Growth of large swarms 

 was fairly uniform up to 140 u. This took about 4 days. Then the size 

 range expanded. Greatest concentration seen was about 2,500 early stage 

 larvae/100 liters. in July. Oldest stages were so scarce that it was nec- 

 essary to pump 500 to 1,000 liters of water to find them. Rarely were more 

 than 5 ready-to-set larvae found/100 liters. Setting occurred over most of 

 summer and in relatively small concentrations. The phenomenal sets of local 

 folklore were not encountered. Larvae of extensive spawnings were found 

 throughout the Harbor and at all tidal stages. Larvae from smaller 



74 



