When dining at a sushi restaurant, you'd expect that the fish you order is the fish you'll be served, but this is not always the case, especially when it comes to white tuna.

The term "white tuna" can mean you'll receive albacore tuna, but it can also refer to escolar, which isn't tuna at all. Often, escolar is mislabeled as white tuna at restaurants.

Escolar is caught as a byproduct of the tuna fishing industry. The fatty, mild-flavored fish is actually two species of snake mackerel and is a budget-friendly sushi-grade fish.

However, 90% of escolar's fat content is a waxy, indigestible substance called gempylotoxin. Consuming it can lead to stomach discomfort and digestive issues.

If you want to eat escolar, keep portions small to stay safe — preferably under six ounces. It's worth noting that Japan and Italy have banned it due to its potential side effects.

The color of white tuna reveals the fish's true identity, as albacore tuna is pale pink, while escolar is opaque white. Check with your server before ordering.