Tuna tastes good for a good reasons and when you know what you are doing it can taste great. It looks pretty standard to find tuna in almost any sushi restaurant all over the globe. There are obviously different types of tuna species, and the costs of a tuna fish corresponds to size, quality and region. There are also many other factors that influence price.

The hands of a sushi chef are one of those cost factors, but the fisherman’s hands and technique make all the difference. The one thing about Japan that separates it from the rest of the world’s fishing community lies in the details. When you see a fisherman working on a Japanese vessel he has a clearly defined protocol. There is little to no margin for error.

Tuna is warm-blooded and their internal temperature remains constant at about 28°C for their whole life. Their average body temperature changes according to the ambient water temperature and their feeding and activity rates.

Under certain conditions, such as during stress and struggle during capture, their body temperature may rise for short periods to 35°C to 40°C. Unlike mammals, tuna have few temperature control methods. One way they lower their temperature is to position themselves in colder water. They conserve their internal heat by a combination of managing their blood flow and body cell function. As a result tuna are usually hotter in their core and cooler toward the extremities.

After death, this elevated body temperature is detrimental to flesh quality as it can speed up the onset and progression of bacterial growth and biochemical deterioration. Before death, tuna can suffer a build up of metabolic products such as lactic acid. This is formed during the struggle as the fish is landed.

Lactic acid is a waste product of muscle exercise and needs to be removed before it causes damage to the exhausted muscle tissue. This damage can include a change in meat appearance from translucent to cloudy, softening the texture and giving a bitter flavor to the meat.