~J 100-ldV 



7350 



Figure 21. —Distribution and abundance of Spisula solidissima in the New York 

 Bight apex. 



FEEDING ECOLOGY: S. solidissima is a filter feeder; it lies 

 near the sediment surface and extends short, fused siphons into the 

 water. Stephens and Schinske (1961) reported that their experi- 

 ments with S. solidissima indicate that, during a 16-h period, the 

 removal of the amino acid glycine from solution took place in the 

 mantle cavity of adult surf clams with an efficiency of 87%; the 

 ecological significance of this remains to be fully examined. The 

 food of larval S. solidissima consists of diatoms, green algae, and 

 naked flagellates (Hirano and Oshima 1963). 



Surf clams, when under stress of crowding or predator attack, 

 may come to the surface and perform leaps of several feet. Preda- 

 tors of this clam include the moon snails, Lunatia hews, in deep 

 water, and Polinices duplicates, in shallow water. Smaller surf 

 clams provide food for fish, including cod and haddock, and for 

 diving ducks (Saila and Pratt 1973). Franz (1977) compared the 

 size distribution of S. solidissima valves with and without bore 

 holes of L. heros. In specimens collected off Long Island, he found 

 that predation by L. heros is largely limited to clams <80 mm in 

 size and under 5 yr of age. However, older and larger clams are not 

 completely immune to attack, since bored valves to 160 mm in 

 length were occasionally observed. 



Thorson (1957) stated that communities where Spisula elliptica 

 is dominant may have extremely high productivities; in European 

 waters, these areas are growth centers for young flounder. The yield 

 to man of S. solidissima-dom'maled bottoms in terms of fish food is 

 probably lower in the Middle Atlantic Bight because much of the 

 area where S. solidissima is most abundant is south of the range of 

 the mass marketed groundfish such as cod, haddock, and yellowtail 

 flounder. 



REPRODUCTION AND GROWTH: According to Ropes 

 (1968). sexes are separate in S. solidissima and it has been reported 

 that two annual spawnings occurred in three successive years off 

 New lersey, a major one from mid-July to August and a minor one 

 in mid-October to November. In a cool year ( 1965). a single spawn- 

 ing was observed during September and October (Ropes et al. 

 1969). Larvae took 19 d to reach setting size in the laboratory at 

 22 C C (Loosanoff and Davis 1963). 



Initial growth is rapid and clams can grow to 4.4 cm by the end of 

 their first year (Yancey and Welch 1968). Clams reach commercial 

 size of about 12.5 cm in 5-6 yr after which they grow at a much 

 slower rate for as long as 17 yr. Maximum length is only 7.5-10 cm 

 for specimens off Cape Cod but is about 17.5 cm for those off Long 

 Island and to the south. 



ADDITIONAL INFORMATION: The modern fishery which 

 developed after World War II utilizes highly developed, efficient 

 hydraulic dredges. Yearly landings of surf clam meats for 1978 off 

 New Jersey totaled 6,904 t, which sold at a price of about SI ,093/t 

 (Current Fisheries Statistics 1978). This was a drop from 5 yr 

 before when total New Jersey landings were 9,792 t, which sold for 

 a low price of about $277/t (Current Fisheries Statistics 1973). 

 Much of the stock in the New York Bight apex is closed to fishing 

 by the U.S. Food and Drug Administration because of bacterial and 

 chemical contamination. 



The surf clam is particularly well adapted to withstand mechani- 

 cal stress, however, little is known about its ability to withstand 

 other types of stress, either as larvae or adults. For example, during 

 the 1976 New York Bight oxygen depletion phenomenon, thou- 

 sands of S. solidissima were found dead during surveys, with some 

 recolonization by juveniles reported in the summer of 1977 (Steim- 

 le and Sindermann 1978; Steimle and Radosh 1979). 



Tellina agilis Stimpson, 1857 



DESCRIPTION: Northern dwarf tellin; 0.8-1.3 cm in length; 

 moderately elongate, compressed, fairly fragile; glossy-white to 

 rose externally with an opalescent sheen. External sculpture of 

 faint, microscopic concentric, impressed lines (Abbott 1968. 

 1974). 



DISTRIBUTION: 



1974). 



Gulf of St. Lawrence to Georaia (Abbott 



HABITAT: Common; in sandy mud, 0.9-45 m (Abbott 1968). In 

 Long Island Sound, Franz (1976) found Tellina agilis to be charac- 

 teristic of medium sand. In samples taken near the mouth of Dela- 

 ware Bay, T. agilis was among the three most numerous species 

 collected, occurring in the transition zone between pure sand and 

 mud facies (Kinner et al. 1974). In Delaware's coastal waters, it 

 was the most abundant and frequently occurring bivalve in clean 

 medium-coarse sand (Maurer, Leathern. Kinner, and Tinsman 

 1979). The occurrence of T. agilis in large numbers throughout a 

 wide sediment range indicates that it has a broad tolerance for sedi- 

 ment particle size. 



Wass (1965) has determined that T. agilis prefers salinities 

 > 18% under natural conditions. However, in the laboratory, it tol- 

 erates a wide salinity range (2.5-30% ). In nature, it may not 

 inhabit its potential salinity range because of biological interactions 

 such as predation, competition from other species, or special envi- 

 ronmental requirements, i.e., high levels of dissolved oxygen, low- 

 levels of suspended sediments, suitable bottom type. etc. (Castagna 

 and Chanley 1973). 



15 



