Fish are very healthy for us. They are good source of omega-3 fatty acids. Two to three times a week, 150 to 175 g, are good.
The average nutrients in 100 g edible mackerel-meat include:

• Water - 68.0 g
• Protein - 18.7 g
• Fat 11.9 g
• Minerals - 1.3 g – sodium 85 mg, potassium 395 mg, magnesium 30 mg calcium 12 mg, iron 1200 micro g, copper 115 micro g, zinc 520 micro g, selenium 40 micro g, iodide 50 micro g.
• Vitamins - vitamins A, B1, B2, B6, B12, nicotine amide, pantothenic acid, biotin, folic acid, vitamins D, E, K
• Cholesterol 75 mg
• Purine 145 mg

Prepare as you like. The fish protein is damaged very quickly in room as well as in warm temperatures. So it must be fresh or frozen before you cook.

Fish is a good food for all.