second study was . Behavior Although mainly found in deep offshore waters, yellowfin tuna may approach shore when suitable conditions exist. Mid-ocean islands such as the Hawaiian archipelago, other island groups in the Western Pacific, Caribbean, and Maldives islands Indian Ocean, as well as the volcanic islands of the Atlantic such as Ascension Island and Saint Helena, often harbor yellowfin feeding on the baitfish these spots concentrate close to the shoreline. Yellowfin may venture well inshore of the continental shelf when water temperature and clarity are suitable and food is abundant. Yellowfin tuna often travel in schools with similarly sized companions. They sometimes school with other tuna species and mixed schools of small yellowfin, and skipjack tuna, in particular, are commonplace. They are often associated with various species of dolphins or porpoises, as well as with larger marine creatures such as whales and whale sharks. They also associate with drifting flotsam such as logs and pallets, and sonic tagging indicates some follow moving vessels. Hawaiian yellowfins associate with anchored fish aggregation devices and with certain sections of the 50-fathom curve. Diet and predation Yellowfin tuna prey include other fish, pelagic crustaceans, and squid. Like all tunas, their body shape is particularly adapted for speed, enabling them to pursue and capture fast-moving baitfish such as flying fish, sauries, and mackerel. Schooling species such as myctophids or lanternfish and similar pelagic driftfish, anchovies, and sardines are frequently taken. Large yellowfins prey on smaller members of the tuna family such as frigate mackerel and skipjack tuna. In turn, yellowfin are preyed upon when young by other pelagic hunters, including larger tuna, seabirds, and predatory fishes such as wahoo, shark, and billfish. Adults are threatened only by the largest and fastest hunters, such as toothed whales, particularly the false killer whale, pelagic sharks such as the mako and great white, large Atlantic blue marlin and Pacific blue marlin, and black marlin. The main source of mortality, however, is industrial tuna fisheries. Yellowfins are able to escape most predators because of their speed, swimming at up to . Unlike most fish, tuna are warm-blooded. Their unique cardiovascular system, warm body temperature, elevated metabolism, and well-developed lymphatic system are all involved in their ability to engage in both rapid bursts and long periods of swimming. When swimming rapidly, a tuna's fins retract into grooves to form a smooth aerodynamic surface and increase its speed, due to