This is Shark *Bait* Week. It’s a bit of a twist on last year’s Shark Stamp Week.
I’ll be sharing some information about shark prey animals that have appeared on stamps from around the world. And sharing stamps, too, of course.
I hope you enjoy this week!
In 2021, I organized the stamps by country since so many issue sets of shark stamps, this time I’m organizing by subject, so the countries will jump around a bit.
Today’s subject is the yellowfin tuna, Thunnus albacares, is also called ahi, from the Hawaiian name for the fish.
This stamp is from Saint Helena’s Marine Life series. It was issued July 12, 1985 and has a Scott number of 436.
The stamp is watermarked.
It is a commemorative with a comb perforation of 13 x 13½, and was printed by offset lithography. It has a face value of 33 Saint Helena pennies.
Yellowfin are one of the larger tunas, and can weigh over 400 lb (180 kg). They can also grow up to 7 ft 10 in (2.4 m) long. Only the bluefin tuna are larger.
Yellowfin are epipelagic fish, which means they inhabit the mixed, warmer, surface layers of the ocean. Tracking has found that yellowfin tuna mostly range in the top 330 ft (100 m) of the water column.
Reportedly swimming depth can vary with time of day. During the night, they stay in water shallower than 289 ft (88 m), but during the day they may spend some time down to 620 ft (190 m).
Yellowfin tuna dive more deeply infrequently, but they can dive to considerable depths. An individual tagged in the Indian Ocean made three dives almost 4000 ft (1,100 m). The deepest yellowfin dive recorded is 5,223 ft (1,592 m.
This stamp from Tokelau’s marine fish series is a commemorative issued on October 3, 2012.
The comb perforation is 13¾ x 13½.
Printed by offset lithography, it has a face value of 40 New Zealand cents.
Despite staying relatively near the surface, yellowfin tuna are found mostly in deeper offshore waters, though they sometimes come inshore in special conditions.
Mid-ocean islands such as the Hawaiian islands, the Maldives, and places such as Ascension Island and Saint Helena, may have schools of yellowfin feeding nearshore where baitfish congregate.
Yellowfin tuna usually travel in schools with similarly sized fishes. Schools of young yellowfin and skipjack tuna are common.
Yellowfin will often school with dolphins and porpoises, as well as with larger whales, and even whale sharks.
The stamp here is from the French Southern and Antarctic Lands tuna fishing series.
Issued on January 2, 2017, this commemorative has a comb perforation of 13¼ x 13
Printing was by offset lithography and recess printing.
The stamp has a face value of 0.44 Euro, and had a print run of 46,000
The fish can also be found around drifting flotsam, such as logs and pallets, even follow moving vessels. Smaller fishes often use such places as shelter, so the predatory yellowfin take advantage of that.
Prey of the yellowfin tuna include other, smaller fishes, pelagic crustaceans, and squid.
Like all tunas, their body shape is adapted for speed, enabling them to pursue and capture fast-moving baitfish including flying fish, sauries, and mackerel. Schooling fishes such as anchovies, and sardines are frequent prey.
Large yellowfin will prey on smaller tunas such as frigate mackerel, and skipjack tuna.
In turn, yellowfin are preyed upon when young by other pelagic hunters, including larger tuna, seabirds, and predatory fishes such as wahoo, sharks, and billfishes.
Adults are threatened only by the largest and fastest hunters, such as toothed whales, particularly the false killer whale, pelagic sharks such as mako and great white, and large marlin.
Industrial tuna fisheries are their most deadly predator, however.
From Madagascar comes this 1982 fishes series stamp, with a Scott number of 650. It was issued on December 14, 1982
This commemorative has a comb perforation of 11¼.
Offset lithography was the printing method, and it has a face value of 50 Malagasy francs.
Yellowfins are very fast fish swimming up to 47 miles per hour (20.8 m/s).
One of the most surprising things, for many, is that tuna are warm-blooded, or endothermic. Their muscle movement at least partly contributes to this. The muscles are in essentially constant movement propelling their bodies through the water, and this generates heat. Their body retains some of this, and they can bring their bodies to quite impressive temperatures. In fact, tuna brought onboard a fishing boat must be quickly iced down so that their body heat does not start cooking the dead fish.
They are a frequently eaten tuna, and yellowfin is widely used in raw fish dishes like sashimi. They are also excellent for grilling, often served seared rare.
Seafood sustainability advocates come to different conclusions about whether yellowfin fishing is sustainable. The Audubon Society lists troll-caught tuna as “OK”, but labels long-line caught as “Be Careful”.
Greenpeace meanwhile, lists yellowfin on its seafood red list.
Despite this bit of controversy, yellowfin is becoming a popular replacement for the severely depleted supplies of southern bluefin tuna.
Thank you for joining me for this, part of Shark *Bait* Week 2022. I hope you enjoyed it
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