An operation can reduce the likelihood of biological contamination by

An operation can reduce the likelihood of biological contamination by purchasing seafood from approved, reputable suppliers

Explanation:

There are many operations that reduce the probability of having the biological contamination.The simple yet effective operations are: cleaning the cooking utensils properly, properly wash hands with soap water before preparing foods, always seek the food from certified suppliers etc.  By following this simple operation one can easily reduce the risk by big amount of having the biological contamination because contamination is caused by the contact of food to the dirty place containing the bacteria and other infectious organisms.