Wash the mackerel, pat dry and cut 3-4 times diagonally on each side.
Cut 4 cloves of garlic into small slices, chop the remaining cloves. Cut the garlic chives into small pieces. Cut 2 lemons into slices, squeeze the third.
Make a marinade from the lemon juice, olive oil, the chopped garlic and half of the garlic chives. Season with salt, pepper and cayenne.
Distribute the lemon slices, garlic slices and the remaining chives in the fish bellies. Pour the marinade over the mackerel. Let it steep in the refrigerator for 3-4 hours.
Before grilling, remove the mackerel from the marinade and grill over medium heat for approx. 20 minutes. Turn more often and brush with the marinade every now and then.
A crunchy summer salad and baguette go well with it.