9-15 



results shown in Table 9-5 indicate that mortality in 1976 and 1977 was 

 siynif icantly lower than mortality in 1975. 



Change in Length (Growth) 



Figure 9-5 shows mean oyster length by month at each station 

 during the period 1974-1977, and Table 9-5 shows net growth (mm) of 

 oysters at each station during the same time period. These data appear 

 to indicate that net growth was high at both stations in 1975, 1976 and 

 1977 although mean length was low in 1977. Net growth in Table 9-6 has 

 not been adjusted for initial length as was done in the covariance 

 analysis test of hypothesis (2) . Table 9-7 expresses the results of the 

 test of this hypothesis (see statistical appendix) as a series of in- 

 equalities relating adjusted net growth and year, while Figure 9-6 com- 

 pares the pattern of growth by station and by year. These results 

 indicate that growth at both stations was greatest in 1976, least in 

 1977 and intermediate in 1975. Thus, yearly variation was highly sig- 

 nificant but between-station variation was not. The station-by-year 

 interaction was not significant at a nominal alpha level of 0.05. 



Within-year growth patterns (Hypothesis (3)) were tested using 

 a complex analysis of variance technique with pairwise multiple compari- 

 sons to determine those months between which mean length differed sig- 

 nificantly. Table 9-8 and Figure 9-7 show the results of this analysis. 

 The multiple comparisons showed that significant growth took place 

 during the same time periods at both experimental stations in 1975, 1976 

 and 1977 with the exception that in 1975 the first significant growth 

 increase took place one month later at Fort Hale than at Harbor Station. 



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