By Scotty Kyle

I am one of the largest, fastest and most aggressive tunas. Almost everyone in the western world has heard of my species, either in the context of sport fishing, or food, and many millions of people rely on us for sustenance. Around the Gulf of Mexico alone, I am reputed to be worth around 7 billion dollars a year to the local economy through “sport fishing” – and then there is the heinous practice of eating my species cooked or even raw as “sushimi”. I am a yellowfin tuna.

Who Are You, Mr. or Mrs. Yellowfin Tuna?

Humans named me Thunnus albacares. The first part of my name puts me in the Genus Thunnus, which also contains most other tunas, and “albacares” refers to my magnificent white meat. All of us, along with most mackerels and bonitos, are part of the Scombridae family, and share some common family features such as body shape.

Anatomy of a Trophy Catch: Slick, Big, Fast 

Cylindrical and elongated, we are built for speed, and everything about us reflects this. Turning sharply is not our strong point, but surprising and catching other incredibly fast fish, like the flying fish, is what we do routinely.

Our eyes are large, round and smooth against the surface of our body, our mouths are not very big and close beautifully into the front of our heads leaving no water resistance. Our fins fold neatly into grooves along our bodies when we move at speed.

Talking of fins, no other fish can equal our distinguishing feature, our magnificent, bright yellow, second dorsal and anal fins. When we are mature, that makes us easy to distinguish from other species, as these fins curl backwards and, at times, even look sickle shaped. This helps us to turn rapidly and also drives our ladies wild.

Our bodies are covered in tough, small, shiny, smooth scales and our upper areas are dark metallic blue while our flanks and bellies are silvery white. The dark protects us from detection from above and our lighter tummies hide us from predators below.

In terms of size, we can reach an impressive 2.4 m. (7 ft. 10 in.) with a greatest mass of 180 kg. (400 lbs.). That’s big, but not quite as big as our cousins the bluefin tuna, who scare us – those can reach incredible sizes of around 450 kg. (990 lbs.). Sadly, as with most of our family, large specimens are now rare except in remote areas as fishing pressure often kills us before we can reach our full potential.

Hunting Strategies: How Yellowfin Tuna Feed and Behave

We are voracious predators and begin life eating plankton as we float in the top layers of the ocean and then we gravitate to eating tiny shrimps and crustaceans. We quickly, however, develop a taste for fish, which become our favourite food items unless a tasty squid or other large invertebrate appears.

Among fish, some of our staple dishes are anchovies and small mackerel, but our absolute favorite is the flying fish. They speed out of the water as we chase them, glide along over the surface where we track them and, as they must return to the water, we are waiting to ambush them.

Our favourite feeding method is to locate a large shoal of small fish and then charge. We usually live and hunt in groups of similar-sized individuals and try and confuse large shoals by darting into them and breaking them into smaller sized groups. We then move this shoal away from the mother shoal and then try to catch individual fish. When our strike is successful, we generally gulp the catch whole.

We are quite tolerant of other predators, and often hang out with other tunas, wahoo, and even dolphins. Hunting together benefits all of us by completely disorientating the prey, confusion reigns, and a true feeding frenzy can result as the prey lose their shoal and are quickly engulfed. This often takes place near the surface, where birds will spot the splashing and join in the fun. Unfortunately, any passing humans can also interfere, and try to catch some of us in turn. 

Yellowfin Tuna Don’t Only Swim Fast: Life Cycle and Breeding

Humans know little of our reproductive behaviour except that we spawn multiple times per year with a peak of activity in summer. They assume that similar-sized individuals gather in large groups near the surface of the ocean and go around each other in circles, releasing eggs and sperm. Fertilised eggs float within the water column and hatch in a few days.

Fish larvae drift with ocean currents, but grow rapidly and quickly learn to feed on any creatures small enough to be swallowed. This is fairly near the truth and the reality is that we yellowfin tuna lead a fast, voracious lifestyle and have an exciting and prolonged sex life.

We grow rapidly throughout our lives and mature at around one metre (3 ft.), but this can be reached at anything from about one to five years. In some areas food is abundant and we reach the adult size quickly, while in others growth is much slower. As we are found around the globe, in both tropical and sub-tropical waters, there is great variation in many aspects of our lives.

Global Hotspots: Best Locations for Yellowfin Tuna Fishing

We have been recorded in over 165 countries, making us one of the most widespread of fish species and, with global catches estimated at over 4.9 million tons, we are one of the most economically important fish species commercially, and probably also from the sport perspective. 

Hawaii and Baja California, Panama, the Gulf of Mexico, much of Australia, southern and eastern Africa, Cape Verde and other Macaronesian islands, the Maldives and Seychelles in the Indian Ocean, are all places where, humans say, there’s good fishing for my species. Some travel even greater distances to the exotic – from people’s point of view – locations like the Ascension Island and Fiji, rather than leave me alone. 

We, in turn, are ready to travel, too, and we are known to migrate massive distances. Off Australia, a cousin that humans have tagged travelled over 1,000 km in a year. However, some of us just wander about over a limited area, and we’re seen as local residents in many places. 

Conservation and Sustainability: Yellowfin Tuna Under Threat

Humans also say that, as we are fast growing and have a high reproductive output, we can be a prime target for fisheries. In reality, we are so popular, and people got to be so efficient in catching us, that our populations are greatly reduced in some areas. It is estimated that our biomass globally has decreased by 50% since 1950. Most commercial fishing for my species is carried out in open areas of the Indian and western Pacific Ocean. The Indian Ocean stocks are under especially severe pressure.

Our biggest threat is from commercial fishing, and this has moved from the traditional line and pole fishing, catching individual fishes, to much more efficient methods such as “long-lining”. Here strong lines, often kilometres long, with many thousands of baited hooks, are set for several hours and then recovered. Smaller boats often work with nets and take catches to large “mother ships”. Large nets, mostly purse seine and gillnets, capture whole shoals. These fish can be sold fresh, frozen or canned.

Humans often worry about “by-catch” in these fisheries as birds, turtles and dolphins are routinely caught on long lines and in nets. Efforts are made to release these species live, but any tuna fishing will result in collateral damage on other species; “dolphin-friendly” methods may actually kill more birds. 

Tactics and Techniques: How to Catch Yellowfin Tuna

Humans seem to want to catch me so much, that they invented numerous ways of catching me, from primitive rod and line setups to enormous seiner nets. Recreational anglers, however, seem to prefer trolling. Those who can’t boast of owning an appropriate boat, hire fishing charters. They cruise at speeds of 5 to 10 knots, dragging behind lures or bait rigs designed to mimic our natural prey. 

Popular artificial lures include cedar plugs, feather lures or skirts, often in vibrant colors like pink, blue, and white to grab our attention in the water. Hard-bodied diving lures, like those with deep-running lips, are excellent for trolling at varied depths. Live bait such as sardines, mackerel, or skipjack is ideal, and even dead baits, including rigged ballyhoo or squid, can be highly effective. 

We have been fished for so often, though, that we can be hard to fool, so the most experienced captains use elaborate setups such as spreader bars or daisy chains. Ingenious anglers often enhance their setups with teasers, splash bars, or birds to create additional commotion, misleading us into thinking that a feeding frenzy is in progress, and attracting whole schools.

The trick in yellowfin tuna fishing is to locate a school, which is often signaled by diving seabirds or pods of dolphins. Modern boats, especially off the Gulf Coast, have advanced equipment that can find our shoals and even deliver tasty looking morsels right in front of our noses. We can be a secretive species, but slowly the humans are getting to know, understand and predict our behaviour and movements.

They know that we are usually in the upper 200 meters of the water column no matter how deep the water. We live mostly in the open ocean and shun shallow coastal waters and reefs and yet we just love some structures. We cannot pass things like buoys, floating logs or oil rigs without stopping to have a good look around.

The Unforgettable Thrill of the Catch

With so much attention from humans, it’s fortunate that we do grow rapidly and recruit well. It is possible for my species to maintain good numbers and sizes if simple management guidelines are implemented, and excesses are avoided. What’s unfortunate is that too few recreational anglers practice catch and release when they hook a yellowfin tuna. Rest assured, I will do my very best to avoid striking anything that looks vaguely like a bait. But it would be even better if humans practiced a little moderation when it comes to catching me – so that my species can keep supplying humans with delicious food and unforgettable thrilling moments while fishing for years to come. 

Next in “Life History of a Fish” series:

Life History of a Fish: Wahoo

By Scotty Kyle

I am a popular, valuable and much sought-after, game fish found in warmer waters throughout the world’s oceans. Scientists call me Acanthocybium solandri and place me in the Scombridae family, along with tunas, barracudas and mackerel. They describe me as an offshore, pelagic species, even though they have little real knowledge of our migratory movements. 

Humans regard our flesh as tasty, with a pleasant texture, and we are one of the top target species for boat-based sport fishing. When we take a bait or lure, the line peels off so rapidly that the reel screams and the angler often also shouts out loudly in his delight – Wahoo! And that’s how I got my name. CONTINUE READING