sample size, was 0.055. Although the ANOVA test detected 

 differences between plots, paired comparisons and multiple range 

 tests could not detect which of the plots differed from each 

 other, again, because of the low power associated with small 

 sample sizes. 



In summary, while there was a significant difference in 

 growth rates between plots for Amblema plicata and while trends 

 are evident for other effects (mortality and damage) and other 

 species, results must be considered inconclusive until we obtain 

 larger samples of marked mussels and allow more time for growth, 

 damage, and mortality to occur. The additional sampling in 1985, 

 and any subsequent sampling, will increase the number of 

 recaptures and enable us to draw more definitive conclusions. 



With the above cautions in mind, we next present graphs 

 showing trends in shell damage, mortality and growth rates of 

 Amblema plicata , the species with the most data, and, where 

 appropriate, all species pooled. In general, most of the other 

 species showed similar trends. Since only five marked mussels 

 were recaptured from the unfleeted upstream control, they were 

 not included in the graphs of recapture data. 



SHELL DAMAGE IN MUSSELS COLLECTED FOR THE FIRST TIME 



The highest damage rate (14 of 116 live mussels, 12.1%) was 

 in the upstream, unfleeted control plot (Figure 4). None of the 

 41 mussels initially collected at the upstream control in spring 



28 



