The first thing you'll need to do before you can smoke your mullet is brine it.
While it might seem odd to take a sea creature out of the ocean only to place it back in a salt solution, this is the best way to introduce the spices and flavors necessary to the barbecuing, as well as to ensure the fish stays moist during the long cooking process.
Rinse the fish inside and out with clean water first, then create a brine solution of 1 cup kosher salt, 1 cup firmly packed brown sugar, 5 crushed bay leaves, and 1 tablespoon of onion powder, mixed with just under a gallon of water in a large bucket.
Mix well, then carefully submerge your fish, adding more water to cover as needed.
Cover the brine and let the fish soak for up to two hours (how long you soak will determine how salty the fish is).
Now that the fish is thoroughly wet, it's time to dry it off. After it's had a chance to brine, remove it from the solution and rinse it off in cold water.
Dry it thoroughly with paper towels before placing the fish on wire racks inside a roasting pan and covering with paper towels.
Place the fish into the refrigerator and let it dry out some (this will take at least two hours).
Near the end of drying, you can start to prep your smoker for cooking.
If you're using wood chips, this is a good time to begin soaking.
Place your charcoal into the smoker and allow it to burn.
The target temperature is around 225 degrees Fahrenheit consistently.
Once this has been reached (and the chips have soaked, if using) fill the water pan and place it and the wood into the smoker, allowing steam and smoke to build up with the lid closed.
Once your fish has dried and the grill is prepped, take the mullet out of the fridge and season it liberally on all sides with freshly ground black pepper.
Let the fish sit at room temperature to warm up slightly before you proceed to cooking.
When warmed slightly, place the fish inside the smoker skin side down and begin smoking with the lid closed.
The target temperature for fish is 145 degrees Fahrenheit, which will take around two hours to accomplish. Check the fish often and monitor the levels of charcoal, wood, and water, adding more of each as needed over the length of smoking.
The fish will be done once the flesh flakes off easily with a fork.
Once the fish has cooked through fully, remove it from the heat and let it rest for ten minutes.