Fish That Is the Source of Most Caviar

Puzzle 7 of Making Sushi Pack

Question is: Fish That Is the Source of Most Caviar

and the answer is: STURGEON

Word Meaning:

STURGEON — Any marine or freshwater fish of the family Acipenseridae that are prized for their roe and are endemic to temperate seas and rivers of the northern hemisphere, especially central Eurasia.

Definition source: Wiktionary (CC BY-SA 4.0)