All fish you catch (aside from Fisher King) are considered fresh fish and will go rotten at reset unless frozen or smoked. To smoke any fish fresh, you need to visit the Smokehouse in Georgetown. You will need 50 study points in Meat Curing in order to be able to enter the Smokehouse. At the smokehouse, you will be able to create Smoked Fish Medleys. The medleys can be used to create troops for the clearing.

For each 10 medleys you smoke it will cost you 1 motivation.

Here is a chart that shows how many medleys each type of fish can smoke "into to."

Bull Head 0.1
Cutterthroat Trout 0.2
Char 0.3
Trout 0.4
Rainbow Trout 0.5
Minnow 0.6
Smelt 0.7
Lukefin Trout 0.8
Black Bass 0.9
Catfish 1.0
Giant Trout 1.1
Darter 1.2
Loach 1.3
Crucian 1.4
Ayu 1.5
Dace 1.6
Sculpin 1.7
Rudd 1.8
Blue Gill 1.9
Dark Chub 2.0
Salmon 2.1
Spotted Trout 2.2
Snakehead 2.3
Great Carp 2.4
Eel 2.5

Another option to smoking your fresh fish is to freeze them so that they do not go rotten. To learn more about freezing, click here.