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Fishery Bulletin 102(2) 



changes in the average size of shrimp within the nursery 

 over time. 



We tested this hypothesis by comparing mean growth 

 rates among months after controlling for initial length as 

 a covariate. For these analyses, the 1998 data from PO and 

 SC were pooled because there was no evidence of a differ- 

 ence in growth rates between these two creeks; the 1999 

 data from EF and WF were analyzed separately because 

 mean growth rates differed between these two systems. 

 After removing the effect of initial size, there was no sig- 

 nificant difference among months in 1998, nor in 1999 at 

 EF, but significant differences in mean growth remained 

 detectable among months at WF (Table 3). The findings 

 from WF also were unusual in that the covariate (initial 

 length) was not a significant factor in the analysis. Post 

 hoc multiple comparisons (Bonferroni, experiment-wise 

 <*=0.05) of mean growth rates among months (without 

 accounting for the covariate) indicated that the specific 

 growth rate in July (0.021) was significantly greater than 

 thai in the other months (0.007 to 0.011). This was the 



only statistically significant evidence of seasonal varia- 

 tion in growth apparently not associated with shrimp size 

 distributions. 



With respect to spatial variation in growth rates of ju- 

 venile shrimp, the most notable observation in this study 

 was the relatively low mean growth rate observed at EF 

 compared to the other sites. This difference could have 

 resulted from the larger mean initial size of individuals 

 tagged at EF (61.3 mm) compared with those at WF (56.0) 

 in 1999. However, a similar difference in mean initial sizes 

 of marked shrimp between tidal creek subsystems (SC, 

 64.2 mm; PO, 59.6 mm) in the previous year did not result 

 in a significant difference in growth rates. When we con- 

 sidered the structural characteristics of each tidal creek at 

 a landscape level, the EF subsystem had the largest tidal 

 drainage area (119.5 ha. ) compared to the other sites ( 58.6 

 to 104.9 ha.), but proportionally less of that area was inter- 

 tidal drainage. There was a stronger correlation between 

 mean growth rate (pooled across all individuals within a 

 creek) and the proportion of the drainage area that was 



