I have been smoking fish for the last 60 years. I have found that using a brine that is so called Saturated Solution of 80 to 90 % is a good rule of thumb. A simple wsy to determine this so called saturated solution, is to add salt to your brine, and stir it in well. Plsce a raw egg into your brine, and if it floats, you have the right amount of salt.
In the Fall, Winter, and Spring, I smoke lots of Steelhead Rainbows tsken from a local stream off Lake Erie. Most fidh on the average run spprox. 4 thru 6 lbs. I chunk the fish, not filleting. If you are first starting out, learn how to make a basic fish brine, and once you find whst you like, stick with it.
I use an approx. 1 1/2 Gal brine consisting of 1/2 gallon generic apple juice, 3 tablespoons ground black pepper, an approx 16 oz box of uniodized table salt ( or Kosher Salt ) approx. 3/4 bag of Dark Brown Sugar, 1 cup regular sugar, 2 teaspoons crushed red pepper, and 1 gal tap water. This 1 1/2 gal brine will do well for any size fish. The most important things to remember is that if you place a sponge into a bucket of water, the sponge can only hold do much water, so as the fish, can only hold so much brine.
Fillets can be soaked in brine fo approx. 4-6 hours snd you sre set to go, while large chunks or whole larger fish will need more time, perhaps overnite thru a second day.
Before you start, cold is the word for brine, and a good safe quality smoking job. I brine in a 5 gal plastic utility pail placed in a refrigerator during warm weather, and in cold winter weather, I sometimes leave outside covered, or in the garage if it is 40 degrees or below. * REMBER * NEVER SCALE YOUR FISH, The skin holds your fish together
After the fish sre brined, take a knife, and run it down the fish piece with the scale pattern , not like the scaling durection. This will remove all brining slime. Quickly rine the fish pieces, don't soak them. I drain them in a collander for 10 minutes, pat dry, and into the cooker they go.
I make gourmet Smoked Trout , and it is all in the flavor, and finish. Use a vinyl glove and rub cooking oil on the skin only to prevent sticking on your racks. Most importantly, Approx two hours before my fish are done, I rub Maple syrup on the entire piece or whole fish. This step gives great color appearance, and that 30.00 per lb Cabelas Gift Box flavor!
* See Pic
Hope this help!
Bear Lake Bob