1956). Wigley (1956) reported that C. pinnulatum is the main prey 

 item of haddock. 



REPRODUCTION AND GROWTH: Cockles grow steadily 

 except during the coldest months. Most are hermaphroditic (Abbott 

 1968). 



Pitar morrhuanus Linsley, 1848 



DESCRIPTION: Morrhua Venus clam: 2.5-3.8 cm in length, 

 oval-elongate, moderately plump; numerous heavy lines of 

 growth. Color dull-grayish to brownish red (Abbott 1974). 



morrhuanus, are important food sources of both the blue. Callinec- 

 tes sapidus, and green. Carcinus maenas. crabs and the drilling 

 moon snails. Polinices spp. (Abbott 1968). 



REPRODUCTION AND GROWTH: The Veneridae are prolific 

 and are adapted to survival under difficult conditions. Sexes are 

 separate and fertilization is external (Gosner 1971). In general, 

 they spawn when the tide is out and usually during a part of the 

 month when the tidal fluctuation is small. The larvae swim and 

 crawl over the bottom until a suitable mud-covered, hard surface is 

 found. They then secrete a byssus and remain attached for about a 

 week until siphons develop (Abbott 1968). 



DISTRIBUTION: Gulf of St. Lawrence to North Carolina 

 (Abbott 1974). 



HABITAT: Fairly common; dredged from sand at 6-183 m 

 (Abbott 1968). 



In the New York Bight apex. Pilar morrhuanus was collected 

 from depths between 19 and 37 m. It inhabited all sediment types 

 but was most common in fine sands; total counts in high and low 

 organic areas were almost equal, however, the largest concentration 

 of P. morrhuanus was found at a high organic station. Pilar mor- 

 rhuanus was the third most abundant bivalve, after Nucula proximo 

 and Tellina agilis. collected in the Bight apex (Fig. 20; Table 1). 



FEEDING ECOLOGY: P. morrhuanus is a suspension feeder. 

 drawing in food-laden seawater. Youna Veneridae. includina P. 



4010- 



Figure 20. — Distribution and abundance of Pilar morrhuanus in the New York 

 Bight apex. 



Spisula solidissima (Dillwyn, 1817) 



DESCRIPTION: Atlantic surf clam; commercial size individ- 

 uals are approximately 12-15 cm in length, the largest bivalve in 

 the Middle Atlantic Bight. Shell is strong, oval and smooth except 

 for light irregular growth lines: color is yellowish white with a thin 

 yellowish brown periostracum (Abbott 1974). Over 70% of all 

 clams harvested in North America are the Atlantic surf clam from 

 the Middle Atlantic Bight. 



DISTRIBUTION: Nova Scotia to South Carolina (Abbott 1968). 



HABITAT: The surf clam is common below the low water mark 

 on ocean beaches. After violent winter storms, they are cast ashore 

 in numbers estimated as high as 50 million clams along a 10 mi 

 stretch (Abbott 1974). NMFS surveys show Spisula solidissima to 

 be abundant north of Hudson Channel in depths of not more than 18 

 m. It also occurs on coarse bottoms of Georges Bank. From New 

 Jersey south, populations extend to depths of 46 m. Very dense 

 beds at an average depth of 12 m occur off Point Pleasant and Cape 

 May. N.J. The beds of the Delmarva Peninsula form a bank 24-28 

 km off the coast at a depth of 27-35 m, and currently support the 

 bulk of the U.S. fishery. 



Abundance of this clam is strongly correlated with coarse sedi- 

 ments. Parker (1967) and Parker and Fahlen (1968) reported that 

 catches in gravel were 2.5 and 2 times those in sand, and 5.5 and 3 

 times those in silt-clay. Their size and burrowing ability give them 

 advantages over other bivalves in unstable sediments. 



In the New York Bight apex, primarily juvenile S. solidissima 

 were collected in depths between 9 and 25 m. They were most 

 abundant in medium and fine low organic sands. Very few occurred 

 in coarse sand and none occurred in silt or high organic areas (Fig. 

 21; Table 1). 



Wass (1965) stated that S. solidissima only occurs at salinities 

 >28% under natural conditions, but may be able to tolerate much 

 lower salinities. Schechter(1956) placed the minimum tolerance of 

 both eggs and sperm of 5. solidissima at "40% seawater" or about 

 15% . Eggs in the polar body stage, however, disintegrate at this 

 salinity. In laboratory experiments. Castagna and Chanley (1973) 

 found that some surf clams survived direct transfer to salinities 

 between 15 and 30% . After acclimation, many survived salinities 

 as low as 10% . The authors believe that 5. solidissima does not 

 inhabit the lower extremes of its potential salinity range because of 

 larval predation. not salinity intolerance. They state that when lar- 

 vae of this species colonize inshore areas, they rarely develop 

 because of intense predation by crabs, carnivorous gastropods, and 

 bottom-feeding fish: this prevents the establishment of permanent 

 populations of 5. solidissima in estuarine areas. 



14 



