Skipjack tuna important prey species for sharks and large pelagic fishes and is often used as live bait when fishing for Marlin. It has no scales, except on the lateral line and the corselet (a band of large, thick scales forming a circle around the body behind the head). It commonly reaches fork lengths up to and a weight of . Its maximum fork length is and maximum weight is . Ageing skipjack tuna is difficult, and the estimates of its potential lifespan range between 8 and 12 years. Skipjack tuna is a batch spawner. Spawning occurs year-round in equatorial waters, but
Kathryn (skipjack) middle, and a flat transom stern. Like all present-day skipjacks she has a stern-mounted push plate to allow operation with a pushboat. She is fore-and-aft-planked, unlike most skipjacks, which are cross-planked. Her flush deck follows the standard skipjack plan, with a main hatch abaft the mast, followed by dredging gear, a smaller hatch, a doghouse over a very low cabin, the steering gear and a set of davits for the pushboat. The cabin is finished with varnished tongue-and-groove paneling, and has a bunk on each side under the deck. Steering gear is hydraulic. The "Kathryn" carries the standard skipjack rig