expt_block  date        mussel_density  prey_eaten  carap_width  sex  parasite  
6           2012-07-20  2               2           11.7         M    No        
6           2012-07-20  4               1           11.6         F    No        
6           2012-07-20  6               0           13           M    No        
6           2012-07-20  8               2           12.6         F    No        
6           2012-07-20  10              0           13.4         M    No        
6           2012-07-20  16              0           10.8         M    No        
6           2012-07-20  24              1           10.1         M    No        
6           2012-07-20  32              8           10.5         F    No        
6           2012-07-20  2               0           11           F    Yes       
6           2012-07-20  4               1           11.1         F    Yes       
6           2012-07-20  6               0           11.7         F    Yes       
6           2012-07-20  8               5           11           F    Yes       
6           2012-07-20  10              1           11.3         F    Yes       
6           2012-07-20  16              0           12.3         F    Yes       
6           2012-07-20  24              5           11           F    Yes       
6           2012-07-20  32              1           11.9         M    Yes