Which of the following is a method of fish preservation?

Concept: Fish preservation is a way of extending the shelf life of fish and other fish products in order to maintain the fish in a healthy and fit-for-human-consumption state after it has been caught. 

Drying, salting, pickling, and smoking are methods used for fish preservation still used today, although the more modern methods of freezing and canning have gained a lot of traction.

Hence, option 4 is the correct answer.