Marinade: In a bowl add garlic, cumin, cayenne and turmeric. Mix this together with the olive oil, salt and pepper.
Take the fish and make some small incisions into the flesh; not too deep we just want to get some flavour into the flesh. Pour over the marinade. Give it a good rub into the fish and place in the fridge to marinade for 30 minutes.
Salad: In a bowl place the onion, tomato, coriander, chickpeas, salt and pepper, olive oil and lemon juice. Mix together and place in the fridge whilst you cook the fish.
Get the BBQ on a medium-high heat and cook the fish for 5 to 6 minutes on each side. The beauty of mackerel is that the skin can really take the heat so don't be scared of the fish burning.