Skipjack tuna are widespread in Australia's oceanic waters. The global distribution of skipjack tuna includes all tropical and subtropical waters except for the eastern Mediterranean Sea and the Black Sea. However, adults are sometimes present waters as cold as 15 C. Skipjack tuna also need a dissolved oxygen level of 2.5 ml per 1 of sea water to maintain a minimum swimming speed and require higher levels when active. This requirement generally restricts skipjack tuna to water above the thermocline and in some areas, such as the eastern Pacific, may exclude them from surface waters. The depth range of skipjack tuna can be from surface waters to 260m during the day, but at night it is much shallower.
Skipjack tuna are a schooling fish having a general tendency to school by size.
Skipjack tuna are thought to spawn in the Coral Sea off north Queensland and in waters off north western Australia. In equatorial waters spawning occurs during all months, but in sub-tropical waters the season is restricted to summer and early autumn. In tropical waters reproductively active female skipjack tuna spawn almost daily. Ripe skipjack tuna eggs are about 1mm in diameter and transparent and buoyant. Estimates of the number of eggs released at each spawning range from about 100,000 eggs for the smallest mature females to 2 million for the largest fish.