7-15 



Annual variability of Mq.i wn;; pronounced at the East Shore tran- 

 sc^ct. It showed highest jiumbers at Long Wharf and East Shore after 

 1973, reaching over 200()/in ' l:or three years in Octob(jr samplings. The 

 high October abundances relative to spring, indicate a heavy spring/sum- 

 mer settlement and overwinter mortality. This coincides with Mya spawn- 

 ing in southern New England from May through November (Ropes and Stick- 

 ney, 1965) . After a planktonic life of about three weeks the larvae 

 settle on a wide range of sediment types and establish themselves as 

 sessile filter feeders where they are preyed upon by birds, bottom fish, 

 Limulus , larger polychaetes, and crabs (TRIGOM, 1973). Individuals 

 normally establish burrows at about 25 cm and subsequently spawn (Dowe 

 and Wallace, 1957) . Size data, as discussed above, indicate that Mya 

 did not establish mature populations on the New Haven Harbor transects 

 studied (Table 7-5) . Mya populations apparently recruit from some other 

 area in New Haven Harbor or Long Island Sound. 



The gem clam (Gemma gemma) was the second most numerous bi- 

 valve in New Haven Harbor intertidal samples. It was most abundant at 

 Sandy Point where it occurred from 1971 through 1973 (Figure 7-2) . In 

 1974 and 1975 Gemma was numerous only at Long Wharf. In 1976 and 1977 

 it was found in low numbers at all stations . Gemma does not have a 

 planktonic larval phase since the young are released from a brood as 

 juveniles and settle in the immediate area inhabited by the adults 

 (Sellmer, 1967). Because of this reproduction mode, dense, highly- 

 localized colonies of Gemma tend to form. Brood release occurs about 

 mid-Slimmer and juveniles may grow to 2 mm by late fall (TRIGOM, 1973) . 

 If initial brood releases occur in mid-summer in New Haven, individual 

 Gemma are probably too small in October to be retained on the 2 mm 

 sieves used in this study. The populations of Gemma are probably sub- 

 ject to the same predatory pressures as described for Mya. 



The macoma clam (Macoma balthica) was abundant at Sandy Point 

 in 1971 and 1972 and at Long Wharf from 1973 to 1977 (Figure 7-2) . 

 Macoma spawns in late spring after which its planktonic larvae live in 

 the water column about a month before settlement. Adults have been 

 reported to live up to 25 years, feeding on detritus and other sediment 



