What is the usual depth limit for the epipelagic zone occupied by yellowfin tuna?

Often down to about 200 meters

Yellowfin tuna predominantly inhabit the epipelagic zone, which is the uppermost layer of the ocean characterized by sufficient light penetration necessary for their primary prey base. This zone typically extends from the surface down to approximately 200 meters. While they are primarily associated with these surface waters where they forage actively, the species demonstrates remarkable vertical mobility. Researchers have documented them capable of descending to depths greater than 500 meters. These deep dives are hypothesized to relate to thermoregulation, allowing them to moderate their body temperature, or to exploit transient deep-water prey aggregations. However, their ecological niche and main feeding ground remain anchored within the 200-meter depth limit of the sunlit zone.