7-7 



Gemma gemma, Ilyanassa obsoleta, and Macoma balthica (Table 7-2) were 

 consistently the most conmon taxa collected. Species richness and 

 density showed seasonal fluctuations with fall maxima. Sandy Point 

 station showed the greatest species richness and highest density of 

 individuals of the three stations sampled (Tables 7-3, 7-4) , while East 

 Shore usually showed lowest numbers and lowest species richness. 



Species density generally increased from spring to fall with 

 low values again the following spring. Fall maxima were related to 

 spring and summer recruitment which was often heavy for certain dominant 

 taxa. Spring recruitment was usually not evident in May because the 

 newly settled juveniles were too small for retention by the 2-mm mesh 

 screen used for sieving. The low spring densities relative to those in 

 the fall seen in many years are indicative of either predation or 

 natural overwinter mortality. The most severe overwinter mortalities as 

 evidenced by reduced spring density occurred at East Shore in 1971, 

 1972, 1973 and 1977. Winter mortality was pronounced in Mya arenaria , a 

 dominant species for which size data are available (Table 7-5) . Mya 

 grow about 10 mm per year, on the average, for about seven years (more 

 in the first year, less after 3 years) (Newcombe, 1935) . Mya in New 

 Haven Harbor seldom survive past the length of 25 mm, indicating mor- 

 tality in either the first or second year. At East Shore absence of 

 clams in 1972 and spring 1973 and smaller clams in spring 1974, suggests 

 an inability to overwinter (Table 7-5) . At Long Wharf, spring clams 

 were consistently larger than fall clams, suggesting overwinter success 

 and growth. High winter mortality occurring at East Shore was probably 

 related to the station's exposure to winter north winds which pile ice 

 on intertidal areas and increase wind and wave erosion. Both Sandy 

 Point and Long Wharf are lee shores with respect to northwest winds and 

 may not be as heavily impacted by winter weather. 



Annual variability in density characterized the intertidal 

 community over the seven-year study period. The overall variation was 

 most pronounced at East Shore and Long Wharf (Table 7-3) due to large 

 fluctuations in Mya density. The highest densities of Mya were observed 



