expt_block  date        mussel_density  prey_eaten  carap_width  sex  parasite  
2           2012-07-18  2               0           12.2         M    No        
2           2012-07-18  4               0           13           F    No        
2           2012-07-18  6               0           11.5         F    No        
2           2012-07-18  8               3           11.6         M    No        
2           2012-07-18  10              1           12.1         M    No        
2           2012-07-18  16              7           12.6         F    No        
2           2012-07-18  24              1           12.9         F    No        
2           2012-07-18  32              0           11.8         F    No        
2           2012-07-18  2               0           13           M    Yes       
2           2012-07-18  4               0           13.1         F    Yes       
2           2012-07-18  6               0           11.4         F    Yes       
2           2012-07-18  8               0           11.9         M    Yes       
2           2012-07-18  10              1           12.5         M    Yes       
2           2012-07-18  16              0           12.6         F    Yes       
2           2012-07-18  24              0           12.2         M    Yes       
2           2012-07-18  32              6           12           M    Yes