To brine the salmon, combine the warm water and the salt in a dish large enough to hold the salmon fillet. Stir until the salt has completely dissolved.
Rinse the salmon fillet and place it, skin side down, in the brine. Allow fish to soak while covered completely in the brine for 20 minutes. Remove the salmon, gently rinse both sides with cold water, and gently dab dry with a paper towel. Set salmon, skin side down, on a wire rack for at least two hours. Your goal is to have a tacky glaze form on the fish - this keeps it from drying out while you smoke it.
While the salmon is in the brine, make your marinade by combining juice and zest from limes, salt, pepper, olive oil, and minced herbs. Allow flavors to develop until fillet is ready.
To smoke your fish, set your smoker to smoke and then once you have a good smoke going, set the temperature to no higher than 200 degrees F. When smoker is ready, place salmon with the skin side down on a piece of heavy duty aluminum and curl up edges to catch any juice. Spoon on marinade and cover the top of the fillet best you can. Do not do this until you are ready to smoke your salmon because the acid from the lime will start working its magic right away.
Smoke in prepared smoker until the internal temperature is about 140 degrees F. I usually never test with a thermometer. I test by evaluating the color and firmness of the fish. You don't want it to flake while on the grill because the cooking process will continue even after you remove it, and if it flakes while on the grill, you've over cooked it. You basically want to remove it as soon as it is minimally done.
You can eat your salmon straight out of the smoker with a squeeze of limes or use it for other recipes like in salads, breakfast frittatas, or salmon dip.