How Old Are Tuna Typically When Caught?

The age of a tuna when it is caught depends heavily on the species, with a range so wide it surprises most people. The skipjack tuna that fills the majority of the world’s canned tuna is typically caught at just one to three years old. A yellowfin pulled aboard by a rod-and-reel angler averages roughly three years of age. At the other extreme, southern bluefin tuna hauled in by Japanese longliners in the Tasman Sea include a significant proportion of fish over 25 years old. The species you are eating, the gear used to catch it, and where it was fished all shift the answer dramatically.

Skipjack, the Youngest Tuna on Your Plate

Skipjack tuna account for more than half of the global tuna catch. They are the default tuna in most canned products, and they are overwhelmingly young fish. Skipjack grow fast, reproduce early, and have comparatively short lifespans. In subtropical waters, young skipjack become vulnerable to fishing gear mainly in the first quarter of each year, meaning the fish entering the catch are often less than two years old.¹ Most skipjack are believed to live no more than about eight to twelve years in the wild, so even the older individuals in the catch are still relatively young compared to other tunas. Their rapid turnover is one reason skipjack populations have generally held up better under heavy fishing pressure than their larger cousins.

Yellowfin Tuna and the Gear Effect

Yellowfin tuna are the second most commercially important species, and they illustrate something that applies across all tunas: the type of fishing gear dramatically shapes the age of the fish you end up eating. A large study of yellowfin caught in the U.S. Gulf of Mexico and western Atlantic found that fish taken by rod and reel had an average age of about 2.9 years, while those caught on pelagic longlines averaged 4.9 years.² The longline fish were also substantially larger on average, around 141 cm compared to 112 cm for the rod-and-reel group.

This two-year gap makes sense when you consider how each gear works. Purse seines and surface gear tend to catch schooling yellowfin near the surface, which skew younger. Longlines set hooks deeper in the water column, where older, larger yellowfin spend more of their time. If you buy a fresh yellowfin steak from a longline fishery, you are probably eating a fish somewhere between three and seven years old. If you eat yellowfin caught by a sport-fishing charter or a pole-and-line vessel, it is more likely two to four years old. Yellowfin can live to about 15 to 18 years, but fish that old are relatively rare in the catch.³

Atlantic Bluefin, the Trophy Fish

Atlantic bluefin tuna are the giants of the tuna world and the fish that command jaw-dropping prices at auction. They are also caught at a much wider range of ages than skipjack or yellowfin. In Norwegian waters, where Atlantic bluefin have recently returned after decades of absence, the fish being caught are predominantly adults between 6 and 14 years old, weighing anywhere from about 120 to 465 kilograms.⁴ In the Mediterranean, where bluefin are caught and transferred into sea-cage ranching operations for fattening, estimated ages of harvested fish ranged from 5 to 18 years.⁵

Atlantic bluefin can live more than 30 years, so even the older fish in those catches are not geriatric by the species’ standards. The fish that fetches top dollar at Tokyo’s Tsukiji (now Toyosu) market is typically a large adult, often over a decade old, because the fat content prized for sashimi and sushi takes years to accumulate. In contrast, the smaller bluefin sometimes caught recreationally off the U.S. East Coast can be as young as two or three years.

Pacific and Southern Bluefin

Pacific bluefin tuna have their own distinct catch-age profile. Recent data from the Taiwanese longline fishery, which targets Pacific bluefin in their spawning grounds, showed a notable concentration of fish aged 8 to 12 years from 2020 to 2023, reflecting a recovery in the spawning stock.⁶ Meanwhile, on the other end of the age spectrum, wild juvenile Pacific bluefin as young as zero to two years are caught off Japan specifically for use as seed stock in aquaculture operations.⁷ So the Pacific bluefin catch spans from juveniles under a year old to mature spawners well into their teens.

Southern bluefin tuna push the age envelope further than any other tuna species. Research using otolith aging showed that southern bluefin live to at least 40 years, which is twice the longevity scientists previously accepted for the species.⁸ The age distribution of southern bluefin caught by Japanese longliners in the Tasman Sea indicates that a significant proportion of the fish in that area are over 25 years old.⁹ When you order southern bluefin tuna at a high-end restaurant, you could well be eating a fish older than many of the people at the table.

Albacore and Blackfin

Albacore, sometimes marketed as “white tuna” in canned products, fall somewhere in between skipjack and bluefin in terms of catch age. A study of North Pacific albacore examined fish ranging from 1 to 15 years old, with an overall average size of about 89 cm.¹⁰ Most albacore in the commercial catch are young adults, roughly two to six years old, though the species can survive to around 13 to 15 years. If you are buying canned “white” tuna, the fish inside is probably in that two-to-six range.

Blackfin tuna, a smaller species found mainly in the western Atlantic, have a similar longevity profile. Recent research in the Gulf of Mexico estimated blackfin at over 13 years old, a big jump from earlier estimates that capped them at about 7 years.³ Blackfin are primarily a recreational catch rather than a major commercial species, and most are probably taken at two to five years of age.

How Scientists Know a Tuna’s Age

You might wonder how researchers actually determine the age of a fish that does not carry a birth certificate. The primary method relies on otoliths, which are small, hard structures in the inner ear of bony fish. Otoliths grow in layers throughout the fish’s life, somewhat like tree rings, and scientists count those layers under a microscope. This technique has been refined over decades and has revealed that tunas across the board live longer than anyone used to think. For years, maximum age estimates for many tuna species were based on limited samples and less precise methods. More recent work with larger sample sizes and validated counting techniques has pushed longevity estimates upward for nearly every major species.

Validation is the tricky part. Counting rings is only useful if you can confirm that each ring really corresponds to one year. One method that has proven effective is post-bomb radiocarbon dating. Nuclear weapons tests in the mid-twentieth century released a pulse of radioactive carbon-14 into the atmosphere and oceans. That pulse peaked in the 1960s and has been declining since. Researchers can measure the carbon-14 level in the core of a tuna’s otolith, which formed when the fish was born, and compare it to known carbon-14 levels in the environment at different dates. If the birth year estimated from ring counts matches the birth year indicated by the carbon-14 signature, the aging method is validated. This approach has been used successfully for Pacific bluefin tuna¹¹ and Indian Ocean yellowfin tuna, where it confirmed otolith-based age estimates for fish between about 2 and 10 years old.¹²

The practical upshot of these validation studies is that the age estimates quoted in this article are not educated guesses. They are backed by independent chemical evidence that the ring-counting approach works. That said, the radiocarbon signal is gradually fading as the bomb pulse dissipates, so scientists are racing to use this technique before it becomes too weak to be reliable.

Why the Age of Your Tuna Matters for Mercury

Mercury accumulates in fish tissue over time through a process called bioaccumulation. Older, larger tuna have had more years to build up mercury from the prey they eat. This is not an abstract concern. A study of reared Atlantic bluefin tuna in the Mediterranean found that total mercury concentrations ranged from 0.49 to 1.60 milligrams per kilogram and showed a clear positive relationship with both the size and age of the fish.¹³ The researchers found that the safety threshold was exceeded in all size and age groups they tested, and recommended limiting weekly consumption to no more than 400 grams.

In practical terms, the species of tuna you choose is a rough proxy for mercury exposure. Skipjack, caught young and small, tends to carry the lowest mercury levels among tunas. Albacore runs higher. Bluefin, particularly large adult specimens, carries the most. If you eat canned “light” tuna (usually skipjack), you are eating a fish that was probably one to three years old and has had comparatively little time to accumulate mercury. If you eat bluefin sashimi, you are eating a fish that may be a decade old or more, with correspondingly higher mercury levels. This is why public health agencies generally advise eating smaller, younger tuna species more frequently and limiting consumption of the larger species.

How Fishing Regulations Shape What Ages Get Caught

Fisheries management bodies set minimum size limits, seasonal closures, and catch quotas that directly influence the age composition of landed tuna. For Atlantic bluefin, the International Commission for the Conservation of Atlantic Tunas (ICCAT) imposes strict size minimums that effectively exclude the youngest fish from legal harvest. In the Mediterranean, the minimum size for bluefin is generally 30 kilograms or 115 cm, which corresponds to a fish of roughly three to four years old. This pushes the average catch age upward compared to what it would be in an unregulated fishery.

For Pacific bluefin, Japan has implemented catch limits on small fish (under 30 kg) to protect juveniles, because the fishery had become heavily reliant on catching very young fish. The goal is to allow more juveniles to survive to spawning age, which for Pacific bluefin is around five to six years. Recent evidence of more 8-to-12-year-old fish in the spawning stock suggests that these management measures may be working.⁶

Skipjack fisheries, by contrast, have relatively few age-based restrictions because the species’ fast growth and high reproductive rate make it more resilient to heavy fishing. The result is that skipjack catches remain dominated by very young fish, which is both an ecological reality and a deliberate management approach.

Tuna Ranching and the Question of “Caught” Age

An increasing share of the world’s high-value tuna, particularly bluefin, passes through aquaculture ranching operations before it reaches consumers. In Mediterranean tuna ranching, wild bluefin are captured by purse seines and then transferred alive into floating sea cages, where they are fattened on baitfish for months or even over a year before slaughter. The fish entering these operations in the Mediterranean have estimated ages of 5 to 18 years.⁵ In Japan, a different model takes wild juvenile Pacific bluefin at under two years old and grows them to market size in pens over several years.⁷

This means the “catch age” of a ranched bluefin can be misleading. A tuna captured at age six and fattened for 18 months is functionally a seven-and-a-half-year-old fish when you eat it, but the initial capture happened at six. The ranching period adds weight and fat but also adds time for mercury accumulation, which is part of why that Mediterranean mercury study found elevated levels even in ranched specimens. For the consumer, knowing whether your bluefin was ranched does not change the fundamental age-mercury relationship: it is still an older, larger fish carrying more mercury than a young skipjack.

When Longevity Estimates Keep Climbing

One of the more interesting trends in tuna science over the past two decades is the steady upward revision of how long these fish actually live. As recently as the early 2000s, southern bluefin tuna were thought to max out at about 20 years. Updated otolith work doubled that to at least 40 years.⁸ Blackfin tuna went from an assumed maximum of about 7 years to over 13.³ Yellowfin and bigeye tuna have both seen their estimated maximum ages revised upward to 15 to 18 years. Researchers have noted that both temperate and tropical tunas appear to have greater longevity than previously believed, and that earlier estimates were constrained by small sample sizes and unvalidated methods.

These revisions matter for fisheries management because population models depend on knowing how long fish live, how fast they grow, and when they start reproducing. If a model assumes a species lives 20 years but it actually lives 40, the model will underestimate how many older fish should be in the population and may set catch limits too high. The southern bluefin tuna stock was severely overfished for decades, and the underestimation of longevity likely contributed to overly optimistic assessments. Getting the age right is not just academic bookkeeping; it has direct consequences for whether a fishery is managed sustainably or driven toward collapse.

1
ICES Journal of Marine Science. Estimation of birthdates and catch-at-age using length frequency analysis (LFA), with application for skipjack tuna (Katsuwonus pelamis) caught in the Southwest Atlantic
2
Marine and Coastal Fisheries. Age and Growth of Yellowfin Tuna in the U.S. Gulf of Mexico and Western Atlantic
3
Marine and Coastal Fisheries. Age, growth, and mortality of Blackfin Tuna in the Gulf of Mexico
4
Fisheries Research. The comeback of Atlantic bluefin tuna (Thunnus thynnus) to Norwegian waters
5
Aquaculture. Age structure and growth of bluefin tuna (Thunnus thynnus, L.) in the capture-based aquaculture in the Mediterranean Sea
6
Fisheries Research. Spawning stock recovery of Pacific bluefin tuna (Thunnus orientalis): Evidence from length, age and catch data of Taiwanese longline fishery in 2010–2023
7
Aquaculture. Detection of bluefin tuna blood flukes (Cardicola spp.) from wild juvenile Pacific bluefin tuna Thunnus orientalis caught for aquaculture
8
Fisheries Research. Age and growth in southern bluefin tuna, Thunnus maccoyii (Castelnau): Direct estimation from otoliths, scales and vertebrae
9
ScienceDirect. Age and growth in southern bluefin tuna, Thunnus maccoyii (Castelnau): Direct estimation from otoliths, scales and vertebrae
10
ScienceDirect. Age and growth of North Pacific albacore (Thunnus alalunga): Implications for stock assessment
11
Fisheries Research. Use of post-bomb radiocarbon dating to validate estimated ages of Pacific bluefin tuna, Thunnus orientalis, of the North Pacific Ocean
12
Marine Ecology Progress Series. Age validation of yellowfin tuna Thunnus albacares in the Indian Ocean using post-peak bomb radiocarbon chronologies
13
PubMed. Mercury concentrations in reared Atlantic bluefin tuna and risk assessment for the consumers: To eat or not to eat?