Why This Type Of Fish Is Considered 'The Pig Of The Sea'

Tuna is of two reputations. Thanks to the marketing job done by Big Sushi and mainstream fish media, it's a luxury food. Yet with regards to the canning industry and casserole country, tuna is a commodity. Hefty whole tunas can sell for millions, but 88-cent tuna keeps dinner affordable. For the fish to be everything to everyone, little of it can go to waste, which is why some people call it the "pig of the sea." Everything from offal to loins to tails  and underrated tuna heads can be used to feed people.

Tuna butchering is done in five primal cuts, before being broken down into a multitude of others. Of those five cuts, you have the back loin, belly loin, pelvic fin, bones, and collar. After these are separated from the carcass, they can be butchered into other cuts. For example, the belly is transformed into a popular and cherished tuna cut called otoro, while the back loin becomes various styles of akami. The top of a tuna's head may instead be butchered for noten, a fatty and rare delicacy, or cheek meat (called hoho-niku or kama, depending on where it's cut from). Even the meat scraped from tuna rib bones finds a purpose. It's called nakaochi, and it's incredibly rich in flavor.

Similar to like pigs, tuna is butchered for its offal, with many organs going on to become delicacies in their own right. For instance, in the Mediterranean, tuna heart is a part of culinary traditions. Sardinians sparingly use tuna heart (known as cuore di tonno) to shave overtop of various dishes after it has been salted, pressed, and cured until hardened.

Unlike pigs, some tuna also carry eggs, which means that roe is a valuable and celebrated offal part often butchered from tuna. In the Mediterranean, this roe is known as bottaraga, and it's cured and toughened up in a similar way to the heart. In Japan or Taiwan, however, tuna roe is known as karasumi. Here, it's a bit stodgier and softer, given that the drying and curing practices are a bit different.

One part of tuna that occasionally makes its way to plates is the milt, or the seminal sacks of male tuna. It is a highly-prized, seasonal delicacy called shirako. The texture and color of shirako is often compared to brain, though the flavor is distinct; it's creamy, custard-esque, and typically served steamed, tempura-fried, or put right on top of sushi.

While you may not find eggs or sperm sacks coming from pigs, other parts of tuna — such as the bones and skin — find similar uses. Though pig skin may become chicharrones or crackling, some innovative chefs have begun to try and use tuna skin in the same ways. Shredded bones, alternatively, find their way into everything from soup and stock bases to fertilizer and soil amendments.