Yellowfin Tuna – Thunnus albacares
Ahi (fire in Hawaiian), yellowfin, Allison tuna (the large adults of this species with long sickle-shaped fins were once thought to be a separate species – Thunnus allisoni.
The most obvious feature of the yellowfin tuna is the yellow sickle-shaped second dorsal and anal fins. There are also at least 15 bright yellow finlets edged with black running along the top and bottom of the body behind the second dorsal and anal fins. The pectoral fins are quite long reaching the second dorsal fin. But they don’t go as far back as the finlets as they do with the albacore. The first dorsal fin has 12-14 spines, and the second dorsal fin has 13-16 rays.
The upper body is black, fading to metallic dark cobalt blue, and then becoming a lighter blue. There is often a yellowish stripe running the length of the body just above the lateral line. The body is metallic silver from the centreline down. The skin is covered with small scales.
There are often 20 or so rows of white spots running vertically from the centreline down under the belly. These spots usually disappear after capture. There is a distinct notch in the centre of the trailing edge of the tail.
Although a powerful, robust tuna, yellowfin are generally more slender than a bluefin or big-eye tuna of the same length.
Finally, unlike the bluefin, there are no striations on the bottom of the liver.
The IGFA All-Tackle World Record for yellowfin tuna is a 176.35 kg (388 lb 12 oz) fish caught by Curt Wiesenhutter off Isla San Benedicto, Revillagigedo Islands, Mexico, on 37 kg (80 lb) line on 1 April 1977. The heaviest yellowfin caught in New Zealand weighed 95 kg and was caught in the Bay of Plenty. However, most yellowfin caught in northern New Zealand waters are much smaller with the average specimen weighing about 15 to 45 kg.
Considered by marine biologists to be a tropical and sub-tropical species, yellowfin tuna are found worldwide anywhere between 18°C – 30°C (62°F-86°F). They are migratory, following warm ocean currents in search of food. Their prey includes flying fish and other pelagic fishes, along with squid and crustaceans.
They usually show up in New Zealand by mid-December and can be found on the North Island’s West Coast as far south as New Plymouth, and on the East Coast as far south as Napier over the summer months. They obviously don’t like colder water. Perhaps with global warming, we may begin to see them further south!
Yellowfin Tuna Fishing Methods:
Lures: Yellowfin will often take trolled lures intended for marlin along with a wide range of other artificial lures. They will also go for trolled dead fish baits and squid. Yellowfin will take poppers with some huge monsters being caught from the rocks, particularly in Australia.
Metal jigs in the 150 to 200g range cast near a “meatball” in the Bay of Plenty and allowed to flutter down like a wounded baitfish have also proven deadly. “Meatballs” are tightly packed terrified baitfish that are being herded near the surface by yellowfin tuna and other predators.
Downriggers: According to expert New Zealand tuna angler and writer Sam Mossman, the use of a downrigger is a big asset when it comes to trolling lures for tuna, and yellowfin in particular. Mossman says that lures trolled with the aid of a downrigger outfish surface lures at a rate of 4:1. A lot of depth isn’t necessary. Around 40-50 feet down to the cannonball is about right, along with a trolling speed of 7-8 knots. Yellowfin have been timed swimming at 40 knots! He says the best lures fished from a downrigger are bullet heads and minnows. Bibless minnows like the Elliot’s Mackerel Mauler can be trolled at faster speeds of up to about 16 knots.
Saltwater Fly: Well-known New Zealand angler Mark Kitteridge caught a 37kg (81 lb 9 0z) yellowfin on 10kg tippet back on 28 February 1999 off Moutohora Island (Whale Island) in the Bay of Plenty. This fish was an IGFA Tippet Class Saltwater Fly Rod World Record world.
Bait: One of the best ways of catching yellowfin tuna is by cubing. This technique entails chopping up oily baitfish, skipjack tuna are ideal, into 0ne inch cubes and dropping them over the side of the boat. As each cube begins to disappear out of sight another is released over the side – so you will need a good supply. At the same time, one of the cubes is rigged with a 5/0 hook and sent over the side with the reel in free-spool. When a tuna takes your hook put the reel into gear and set your hook.
Yellowfin tuna are very rapid growing. According to the International Game Fish Association World Record Game Fishes, is not unusual for a four-year-old fish to weigh 63kg (140 pounds).
Although subjected to very heavy commercial fishing, particularly in the Pacific, the species appears so far to have withstood this, although numbers have been reduced over the last couple of decades. They no longer appear in the Bay of Plenty in the numbers they once did.
Working in favour of the yellowfin’s survival is that 1. They breed at a young age from two years onwards. 2. As mentioned above they are fast-growing. 3. They are also prolific spawners with females producing over one million eggs per week for several months during the breeding season.