All fish (aside from Fisher Kings) that you catch are considered fresh fish and will turn rotten at reset unless you smoke them. With the addition of Fishology, you have the ability to temporarily store any fish you catch in a freezer at the Hot Buns Bakery. For each class you have studied in Fishology, you will be able to store one fish, up to a maximum of 1,000. Any fish stored in the freezer will not go rotten, so if you do not want to smoke your fish right away, or would like to try selling fresh, you can list them on the marketplace and then (if unsold), place them in the freezer right before reset. For more information on smoking fish, click here.