is that the name for white tuna, or albacore? i'm confused, because i don't think this was albacore--this was very different from albacore tuna i've had, the kind you eat with ponzu sauce. the texture of this particular piece of fish was more like mackerel (saba), but the taste was, like i said, buttery and sweet.

White tuna is a term that may apply to two different species eaten in Japanese cuisine :

* Albacore tuna, Thunnus alalunga - the pale-fleshed tuna favoured by the canning industry, also known as shiro maguro, bin-naga maguro, or bincho maguro
* Escolar, Lepidocybium flavobrunneum - which is a snake mackerel, not a tuna. It has been banned in some countries, including Japan, because of the laxative effect of the wax esters in its flesh.

"Super white tuna" refers to the escolar but not the albacore.

Escolar is consumed in several European and Asian countries, as well as in the USA, sometimes raw as sushi or sashimi. It may be sold as "white tuna" - a term also used for the albacore - or as "super white tuna" to distinguish it from the albacore.[1] Escolar is also sold misleadingly as "butterfish", "oilfish" and "Hawaiian butter fish"; in Hawaii and Fiji, it is known as walu. Like oilfish, a related species with similar consumption consequences, Escolar is also sometimes deceptively sold under the name of an entirely different species of fish, most commonly "codfish" or "orange roughy".

Strictly Speaking COLOR of the fish:
Which is the semi-translucent, and which is the *actually opaque* white?

I've had the semi-translucent "white tuna" for decades...but only this past year been sevred the *actually white in color* tuna - which was REALLY delicious!