5-36 



navalis disappeared at all stations. The reason for its disappearance 

 is not clear, but other studies have recorded wide fluctuations in the 

 Teredo abundance pattern in the Long Island Sound area (Clapp, 1937) . 



Mytilus edulis 



Mytilus edulis, the common blue mussel, is widely distributed 

 around the world in temperate waters (TRIGOM, 1973) . Distribution at 

 New Haven Harbor showed abundances decreasing from outer to inner harbor 

 stations for all years (Figure 5-14) . 



Mytilus is considered to be fairly tolerant of organic pollu- 

 tion (Anger, 1976), but is sensitive to high summer temperatures. The 

 optimum temperature for the species is between 5-20°C (TRIGOM, 1973) 

 (sometimes exceeded by late summer temperatures in New Haven Harbor) , 

 and it has an absolute upper lethal temperature of 30°C (Van Winkle, 

 1973 in NAI, 1977b). The adult mussel's ventilation rate drops at 

 temperatures in excess of 20°C (Widdows , 1973). Mytilus spat, however, 

 live four times as long as adults at 28 °C (Pearce, 1969) . Settlement of 

 mytilids is largely temperature dependent and does not normally begin 

 until early summer when water temperatures exceed 13°C (WHOI , 1952). 



New Haven Harbor Mytilus distributions were consistent with 

 other observed mytilid distributions in Long Island Sound. Short-term 

 panel data (Figure 5-3) indicated that settlement occurred primarily in 

 the summer but overlapped the spring and fall of some years. Millstone 

 Harbor panels showed that Mytilus settled in September (Battelle, 1974). 

 Mytilus is common in Long Island Sound, occurring at Bridgeport (NAI, 

 1973b) , Millstone, and New Haven Harbor; it is absent only at Stamford 

 (NAI, 1973c) . Within New Haven Harbor, Mytilus showed percent occur- 

 rences of 64, 35 and 22 percent at Fort Hale, Harbor Station and Long 

 Wharf respectively (Table 5-5) . Abundances also showed a gradient 

 decreasing from Fort Hale to Long Wharf (Figure 5-14) , probably related 

 to poorer water quality in the inner harbor. 



