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Aggregations of this species tend to be associated with convergence, boundaries between cold and warm water masses (i.e., the polar front), upwelling and other hydrographic discontinuities. Normally inhabit waters with surface temperatures of 20°C to 30°C (Ref. 28951). However, adults are sometimes present in waters as cold as 15°C (Ref. 168, 28950). Stay near the surface at night. School near the surface with birds, drifting objects, whales, sharks, and other tuna species and shows characteristic behaviors like jumping, feeding and foaming. Opportunistic feeders preying on any forage available. The feeding activity peaks in the early morning and in the late afternoon.
Skipjack tuna also need a dissolved oxygen level of 2.5 ml per liter of sea water to maintain a minimum swimming speed, and require higher levels when active (Ref. 28952). 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 (Ref. 28952).
The warm East Australian Current distributes skipjack tuna larvae into subtropical waters off eastern Australia (Ref. 28956). The larvae are generally limited to the upper 50 m of water and are most common in the sub-surface layers (Ref. 6390). Juvenile skipjack tuna less than 15 cm TL inhabit the same areas as larvae but generally move to cooler waters as they grow to maturity (Ref. 28956).
There is little information on migration patterns for skipjack tuna in Australian waters. Skipjack tuna tagged in the Coral Sea, off Norfolk Island and off New South Wales have been recovered in waters off the Solomon Islands, New Caledonia, French Polynesia and New Zealand (Ref. 28959). The recapture in Australian waters of a few fish tagged in New Zealand and Papua New Guinea indicates that there could also be significant movement of skipjack tuna into the Australian Fishing Zone from the greater South Pacific (Ref. 6390). Epipelagic oceanic. Forms shoals associated with flotsam and whales. Distribution of adults is dependent on temperature within 15°C isotherm. Feeds on pelagic fishes, crabs, larvae, anchovies, krill and squids. Feeding usually occurs at moderate depths in the water column, peaking in the early morning and late afternoon (Ref. 9773). |