Even with “white tuna,” not everything is always as it seems. For a myriad of unknown reasons, restaurants will sometimes sell something under a different name, confusing the customer (at best) and hurting them (at worst). Often, they get away with it, but sometimes… Well… You read the news.
I bring this up because there is an item often served at sushi restaurants called “white tuna” (shiro maguro), or “super white tuna,” that is sometimes supposed to be albacore tuna, which is very light in color (hence why it is called white tuna) on the menu. However, sometimes you may be served a different fish, called “escolar” (AKA “butterfish”) which is often called super white tuna) however I can’t begin to tell you how often I’ve seen escolar served but simply called “white tuna” on the menu. When I order white tuna I always ask the staff if it is escolar or albacore, so it actually is easy to clear up any confusion should you be ordering this item. Legal requirements aside, it’s bad enough to sell a product that people think is something a different fish, but it is particularly significant with escolar, as some people just aren’t able to handle that the different types of fats in the fish very well. As evidenced by an Australian Government’s article warning people of the issue, there are oils and various fatty esters in that fish which are not in most fish, or in the same quantities, which can cause significant gastrointestinal distress in some individuals.
Even if you are able to eat a small portion of escolar with no issues, in larger quantities if eaten in quantity *that* may lead to spending an evening in the washroom. This will not be a fun time if you are planning a night out and are less able to digest the types of fats in this fish efficiently. Of course if you are of the perspective, many a not very nice practical joke has been played on people by others loading their unwitting friends’ plates with super white tuna in anticipation of the results. I don’t find it to be a particularly funny thing to do to someone, but the results are very real and can be quite distressing for some.
Sushi can confusing enough for newcomers, and even those who are very familiar with the dish are sometimes not aware of practices such as this. And this is not to say that all white tuna is escolar and every restaurant serves escolar without including the word “super” in the item name, but you never know, so it’s typically good to ask. But if you happen to get it as a surprise, and you have a more sensitive tummy, you’ll unfortunately know soon enough.