5-35 



Teredo navatis 



Teredo naval is , the shipworm, is common on the east coast in 

 temperate waters (Turner, 1966) . It was an abundant species in New 

 Haven Harbor prior to its sudden absence from the panels beginning in 

 September 1976. Recent data (July 1978) from subsequent studies in New 

 Haven Harbor indicate a return to previous densities (NAT, in prepara- 

 tion) . Figure 5-13 shows a decreasing abundance gradient from Fort Hale 

 to Long Wharf, which may be related to poorer water quality in the inner 

 harbor . 



Success and cosmopolitan distribution are attributable to the 

 habit of brooding young, and the wide salinity and temperature tolerance 

 of T. navalis (R. Turner, 1966) . Roch (in Clapp, 1937) reported con- 

 siderable tolerance to low dissolved oxygen and salinity and attributed 

 this to the ability of T. navalis to seal off its burrow in an incom- 

 patible meditim; it was observed to withdraw for up to 33 days in poor 

 conditions. Boring activity decreased in low-salinity water, silty con- 

 ditions, or temperatures less than 5°C or greater than 25°C (Roch, in 

 Clapp, 1937). T. navalis normally spawns at temperatures between 17.5 

 and 30°C and retains the embryos in burrows, releasing larvae from 13 to 

 30°C (Culliney, 1975). 



Distributions of T. navalis in New Haven Harbor and greater 

 Long Island Sound were consistent with literature reports. Percent 

 occurrence values were 65, 62 and 32 percent at Fort Hale, Harbor Sta- 

 tion and Long Wharf, respectively (Table 5-5) . Figure 5-13 indicates 

 early summer maxima at all stations with decreases in August and sub- 

 sequent increases in the fall. Data from Niantic Bay (Battelle, 1974) 

 showed consistent monthly infestation with a maximum in July followed by 

 an August decline. Short-term panels in New Haven Harbor showed Septem- 

 ber and October settling in 1971, 1973, 1974, 1975 (Figure 5-3). 

 Niantic Bay data for 1973 indicated August and (primarily) September 

 settlement. Teredo settled at a similar time in a New Jersey estuary 

 (Hoagland, et al., 1977). After August 1976 in New Haven Harbor, T. 



