9-19 



DISCUSSION 



Much work has been done on the biology of Crassostrea vir- 

 ginica, but little of it deals with the hypotheses and variables that 

 have been addressed in this study. Most of this historical work has 

 dealt with the commercial aspects of oyster development and culture 

 (MacKenzie, 1970a, b, 1977a, b; Loosanoff, 1932, 1965, 1966). Galtsoff 

 (1964) summarized the Icnowledge of oyster biology and included a section 

 in his monograph on the effect of "pollution" on oyster populations. 

 Many recent investigations focus on the effect of changes in specific 

 physical or chemical parameters on oyster populations (Davis, and Cala- 

 brese, 1964; Lough, 1975; Frazier, 1975; Diaz, 1968) . As previously 

 described, this study investigates the potential impact of the operation 

 of an electric generating station on oyster growth and mortality in New 

 Haven Harbor. Three factors are discussed below with respect to the 

 determination of possible pre- and post-operational effects of the New 

 Haven Harbor Station, and in relation to the hypotheses and variables of 

 this study. These factors are mortality, growth and condition index. 



Mortality was statistically analyzed for the years 1974-1977 

 and found to be independent of station but dependent on year. This 

 indicates that differing environmental conditions at the two experi- 

 mental sites, including any environmental modification due to the oper- 

 ation of New Haven Harbor Station, had no effect on overall oyster 

 mortality. Mortality was significantly higher in 1975 at both sites 

 than in any other year tested. This may have been associated with the 

 low condition indices observed in the initial control oysters in 1975 

 (Table 9-1) . Since mortalities were high in June and July (Figure 9-4) 

 it is possible that the oysters purchased were not as healthy as in 

 previous years, and thus were more easily subject to disease or preda- 

 tion. Data from several other program elements were examined to deter- 

 mine if there was any correlation between the observed high oyster 

 mortality in 1975 and variations in occurrence of known predators or 

 food supply. Table 9-9 shows monthly measurements of chlorophyll a for 

 1974-1976 at Harbor Station. The patterns for all three years are quite 



