New Zealand Sea Fishes

Skipjack Tuna – Katsuwonus pelamis – Powerful barrel-shaped body

Skipjack Tuna – Katsuwonus pelamis

Other Names:

Arctic bonito, oceanic bonito, striped tuna, or victor fish. Aku (Hawaiian). Skipjack is a different species from bonito.

Recognition Features:

The upper back of the skipjack tuna is a dark blue/black colour. The flanks and underbelly are silver/white. There are four to six horizontal lines running along the sides below the lateral line. Freshly caught skipjack can appear a brilliant shimmering metallic silver colour. The presence of stripes on the belly and none on the back make them easy to distinguish from and other tuna species. The pectoral, dorsal and anal fins are all short compared with other tunas. 

Although skipjack caught in the western pacific can reach 35kg (80lb), those caught in New Zealand waters are generally juvenile fish measuring between 45 and 60cm in length and weighing between 2.5 kg and 7.5 kg.

In the 2000 edition of the World Record Game Fishes published by the International Game Fish Association the heaviest skipjack tuna recorded was a fish weighing 19kg (41 lb 14 oz) at Pearl Beach, Mauritius on 12 November 1985 by Edmund K.R. Heinzen.

The 1991 edition of the New Zealand Record Big Game Fishes booklet published by The New Zealand Big Game Fishing Council (INC), as it was known then, records the heaviest skipjack as a fish weighing 8.95 kg (19 lb 11oz) caught by G. Hill on 6kg line off Whakatane on 13 April 1989. 

Skipjack Tuna Distribution:

Found worldwide in tropical and subtropical seas. They are a wide-ranging, schooling, pelagic, deepwater species. In the Pacific and Indian Oceans skipjack often schools with yellowfin tuna (Thunnus albacares)

Skipjack tuna is another one of the many fish species that can only be found in the warmer waters off the North Island coast.  We just don’t get them around the South Island where the sea temperatures are too cold.

They migrate south to northern New Zealand in search of prey during the warm summer months – between late December and early April. Water temperature is important with their expected range, according to Peter Goadby in Saltwater Gamefishing Offshore and Onshore, being between 15℃ and 30℃. This species undertakes considerable long-distance migrations. 

On the Talleys.co.nz website it says that water temperature needs to reach 19 degrees Celsius before they appear. Certainly, most of the information I have read on this species says that 19℃ is the magic water temperature that must be reached in our waters for skipjack tuna to be present. Water temperatures vary from year to year so the timing of their arrival and departure depends on sea conditions.

Skipjack tuna have been caught as far south as Cape Farewell at the northernmost tip of the South Island. 

Known areas where you can expect skipjack in New Zealand are off Great Barrier Island, the Bay of Plenty, with schools reaching as far south as Gisbourne of the East Coast, and New Plymouth on the West Coast.

Skipjack Tuna Fishing Methods

Commercially, skipjack is caught by purse seine netting at depths between 150 and 250 metres. They are also taken commercially by pole-boat fishing in which berley is tossed from the vessel to keep the skipjack interested. They are then caught with a small wooden hookless lure trolled behind the fishing boat with a long pole and short line. The tuna are then “flicked” up onto the deck by the fishermen. Pole-boat fishing is obviously exhausting and labour intensive, though a highly productive fishing method.

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Sport anglers must be aware that skipjack tuna have relatively soft mouths. If played too hard on heavy gear the hook can be ripped out of the fish! 

The most common way sport anglers catch this species is with trolled lures. Smaller sized lures in the 50mm size (two-inch) work best for both trolling and spin fishing. Pink or silver lures are usually effective. Renowned New Zealand angler and fishing writer Sam Mossman in Serious About Gamefishing – Bluewater Techniques for New Zealand recommends anglers use a couple of metres of clear 24kg monofilament as a leader when trolling. This will not only prevent abrasion on the line but will also act as a bit of insurance should something larger hit the lure! 

General:

Skipjack feed on small fishes and crustaceans. While in New Zealand waters their main food source is euphausiid shrimp Nyctiphanes australis – also known as krill or whalefeed. Great numbers of these reddish coloured shrimps form enormous clouds in the sea. During summer many of the kahawai, mackerel, skipjack tuna and other pelagic species caught are literally stuffed to the brim with these little shrimps. 

The flesh of this tuna species is dark red with a medium texture that whitens when cooked. Tuna steaks sold in South Island supermarkets over summer sell for NZ43.00 per kilo making them one of the most expensive fish you can buy in most stores! Skipjack is good eating if cleaned and chilled quickly after capture. However, many recreational anglers regard their flesh as oily and a bit soft preferring the better-eating quality of albacore tuna instead.

The smaller skipjack is pound for pound one of the most powerful fish in the sea. Their red flesh is nearly all muscle making them an exciting prospect for anglers when taken on lighter spinning gear and saltwater flyfishing tackle.

Interesting Facts

Skipjack tuna are extraordinarily prolific breeders. A female can produce a million eggs every day during the breeding season for months on end. They breed at two years of age and life for about four years.

This species can maintain its body temperature as much as 15℃ higher than the surrounding water temperature. Their biology means they can swim faster and for longer than other cooler blooded pelagic predatory species like mackerel and kahawai for example. This feature gives the powerful little skipjack a definite edge in the battle for survival when it comes to following and catching its prey. 

Skipjack Tuna as Bait

 The species is held in high regard by anglers as live and dead bait for big game species including billfish and sharks like the mako and porbeagle. 

Skipjack makes excellent oily cubing bait for other species of tuna, as well as trevally, snapper, and most other desirable target species.

The oily skipjack makes great surfcasting bait but can easily become mushy after being frozen and thawed in the hot sun.

Video: Commercial Pole-Boat fishing for skipjack tuna.

This post was last modified on 02/03/2021 2:36 pm

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