I work at an incredible sushi restaurant, and I can tell you this is very poor quality sushi. What sushi place PRE CUTS their fish!!!!!!! And beware of their super white tuna! Sometimes it's under the name "butterfish," "oilfish," or "waloo/walu." Sushi restaurants occasionally serve it as "super white tuna" or "king tuna", and it's actually Escolar. It's a very cheap fish!
Escolar is a type of snake mackerel that cannot metabolize the wax esters naturally found in its diet. These esters are called gempylotoxin, and are very similar to castor or mineral oil. This is what gives the flesh of escolar its oily texture. As a result, when full portions of escolar are consumed, these wax esters cause gastrointestinal symptoms.