Water-soaked is good. As for the nutritional value, in layman's terms, tuna is rich in protein, fat, vitamin D, and calcium, phosphorus and iron and other minerals are also high; tuna fish back contains a large number of EPA, the front of the middle abdomen is rich in DHA, the proportion of DHA contained in the fish is the crown, is an excellent brain food; tuna contains a large number of myoglobin and cytochrome, fatty acids are mostly unsaturated fatty acids.