Fillet the fish. Keep the skin on the mackerel and make sure to remove the blood line on each fillet. That is the center line on each fillet and can be removed by cutting down both sides of it at an angle and lifting it out.
Sprinkle some salt in a non-reactive dish. Lay the fillet, skin-side down on the salt, and sprinkle some more salt on top of the meat. You only need a little bit of salt. The salt will draw out residual moisture and allow the fish to form a sticky pellicle which will help the smoke adhere.
After 5 minutes, remove the fillet and rinse it thoroughly. Pat it dry with a paper towel.
Brush the skin side of the fillet with olive oil. This will minimize the chances of it sticking to the grill grate.
Add wood chips to the smoker. Aim for a slow and steady trickle of smoke. You don't want large, billowing clouds.
Let the fillet smoke for about two hours, or until the internal temperature reaches 160°F. Remove and serve.
Notes
Selection - Ideally, Spanish, King or Cero Mackerel will be used, but other fish with higher oil contents can easily be substituted.Smoking - If you have never smoked mackerel, then use a light fruit wood like apple, cherry or orange. Too much smoke will over power the delicate fish flavor. Storage - Use in fish dip or add to plastic containers with rice and veggies for lunch throughout the week. If you aren't going to use it all within a few days, wrap in Saran and store in a freezer safe bag for a couple of months.