expt_block  date        mussel_density  prey_eaten  carap_width  sex  parasite  
12          2012-07-27  2               1           11.9         M    No        
12          2012-07-27  4               2           13.3         M    No        
12          2012-07-27  6               0           12.5         F    No        
12          2012-07-27  8               3           11.6         F    No        
12          2012-07-27  10              5           12.6         M    No        
12          2012-07-27  16              5           11.2         F    No        
12          2012-07-27  24              7           11.7         F    No        
12          2012-07-27  32              10          14.8         M    No        
12          2012-07-27  2               1           10.3         M    Yes       
12          2012-07-27  4               0           9.5          F    Yes       
12          2012-07-27  6               1           12.4         M    Yes       
12          2012-07-27  8               2           11.4         F    Yes       
12          2012-07-27  10              1           9.8          F    Yes       
12          2012-07-27  16              3           12.6         F    Yes       
12          2012-07-27  24              1           11.9         M    Yes       
12          2012-07-27  32              2           11.6         F    Yes