Tuna
Tuna are a type of highly migratory saltwater fish that inhabit tropical to warm temperate waters around the world. They are heavily fished and support major fisheries around the world, but overfishing is putting their safety at severe risk.
Agile, fast predators, with streamlined, torpedo-like bodies, the various species of tuna feed mainly on small fish, crustaceans, and shellfish. Most tuna are offshore, ocean pelagic fish, living in open ocean waters away from the coast.
Tuna are in the mackerel family, Scombridae. There are fifteen species in total, of which eight are considered “true tuna”. These are included in the genus Thunnus. True tuna that can be found in the waters of the Pacific Northwest include the albacore, Pacific bluefin, bigeye, and yellowfin tuna. Albacore tuna is the primary species in the Pacific Northwest and supports a fishery; the other species, along with two more species from the greater tuna family, the skipjack tuna and the Pacific bonito, are rare and occasional visitors.
Warm-blooded fish
Tuna are special in that although they are technically cold-blooded, they can regulate their body temperature to maintain it at a higher level than the water surrounding them thanks to a specialized circulatory system.
As a result, it is especially important that tuna are processed correctly when caught and that their body temperature is lowered quickly to prevent damage to the fish. Tuna should be bled, gutted, and iced, ideally in a saline solution, as quickly as possible. It’s a good idea to ask about what methods were used when purchasing a whole fish.
Species
Tunas
Albacore tuna (Thunnus alalunga)
Pacific bluefin tuna (Thunnus orientalis)
Rare species
Yellowfin tuna (Thunnus albacares)
Bigeye tuna (Thunnus obesus)
Skipjack tuna (Katsuwonus pelamis)
Bonitos
Pacific bonito (Sarda lineolata)
Albacore tuna
Albacore tuna (Thunnus alalunga) are the smallest of the true tunas, growing up to about 1 m (3 ft) in length and weighing 40 kg (80 lbs). Excluding bonito, albacore makes up less than 5% of the total global tuna catch (skipjack makes up a whopping two-thirds).
Albacore are fished in the Atlantic, Indian, and Pacific oceans, with majority caught in the Pacific Ocean. For our purposes, we’re looking at the North Pacific albacore population. In recent years, about 66% of the albacore caught in the North Pacific Ocean was landed by Japanese fisheries, followed by the United States with about 14%. More than three-quarters is caught south of Washington state; in the Pacific Northwest, albacore is primarily landed in Oregon waters.
The species is currently not considered threatened. It is thought that albacore tuna are more resilient due to their quicker growth rate and reproductive cycle (in contrast with bluefin tuna). North Pacific albacore stocks are currently not considered overfished, but proper management is key to their future sustainability.
Albacore season
Like other tuna, albacore are a highly migratory species and travel long distances over the course of the year as they follow prey and warmer currents.
Young albacore tuna begin to migrate from Japan to the Pacific coast of the United States in late spring and early summer. There is no set season for tuna off of our coast, but it usually starts somewhere around June or July. The season can last until October, with the peak season usually in August and September. Albacore then return to the western Pacific Ocean for fall and winter.
Cooking with albacore
In the US, people are used to eating albacore tuna as a canned fish; most canned tuna is either albacore (often labelled “white tuna”) or the related skipjack tuna (often labelled “light tuna”). However, most of the canned albacore in stores is sourced from South Pacific stocks.
Although commonly canned, albacore meat is high in fat and has a firm texture, which lends itself very well to grilling or raw preparations. For a long time, albacore was not considered a good sashimi fish in Japan and it is still looked at as a lower-quality option, but then again, bluefin tuna suffered from a similar attitude for years, and only gained popularity after World War II. In fact, our local fish are particularly well-suited to raw preparations due to their higher fat content. Our locally-caught albacore is especially high in healthy fats because the fish migrate to our waters to feed on schools of anchovies and sardines. Fat levels in albacore tuna increase when they feed on these fish and are known to peak in the months they are caught in the Pacific Northwest.
Mercury concerns
Many fish accumulate mercury in their flesh as they get older. Because tuna are predator species close to the top of the food chain, the concern is even greater than for small fish; predator fish ingest greater amounts of mercury. Fortunately, albacore tuna from the US Pacific coast are generally juveniles which haven’t had as much time to accumulate mercury: a study from OSU found that locally-caught albacore contained less than half the mercury found in canned albacore tuna.
Related species
The Pacific bluefin tuna is the second-largest tuna species in the world. The largest recorded specimen was 3 m (9.8 ft) in length and 450 kg (990 lbs), though they are normally around 1.5 meters (5 ft) and 60 kg (130 lbs) when mature. The Pacific bluefin tuna (Thunnus orientalis) is best known for its use in sushi; over three-quarters of the commercially fished Pacific bluefin tuna and related (and even larger) Atlantic bluefin tuna is consumed in Japan. The fish is threatened by overfishing and is considered an unsustainable choice of fish. Its habitat ranges up to Alaska and is occasionally caught by fishermen, but it remains an uncommon fish in our region and is mostly likely to be found in the Northern California region of the Pacific Northwest.
Interestingly, archeological evidence of bluefin tuna fishing has been found in middens in northern Washington and British Columbia, which seems to indicate that indigenous groups in those areas had access to the fish prior to the late 1800s. It is possible that the disappearance of bluefin tuna on our coasts is tied to the increase in fishing of the species elsewhere.
Rare tuna species
Two species of true tuna, the yellowfin tuna (Thunnus albacares) the bigeye tuna (Thunnus obesus) are commonly known as “ahi” in Hawaii. Yellowfin tuna, in particular, is a popular choice for sushi and sashimi.
Both species are found primarily in tropical and subtropical waters. Restricted by water temperatures, their presence north of Southern California is associated with El Niño events that bring warmer water into the Northern Pacific. Even with such events, these fish are exceedingly rare and unlikely to be seen above Northern California.
Katsuwonus pelamis, the skipjack tuna, is best known for its use in “katsuobushi", a fermented and smoked fish product used frequently as a broth ingredient in Japanese cuisine. In the Pacific Northwest, though it has been sighted up to northern Washington in El Niño years, it’s a very rare species and there are very few reports of fishermen catching them.
Bonito
Bonito are in the Sardini tribe rather than the tuna tribe, Thunnini, which includes all of the other species listed in this article. However, evolutionary they most closely related to tunas, so I’ve chosen to include them here.
Sarda lineolata, the Pacific bonito, is an inshore species related to tuna. It was formerly considered a subspecies of the South American Sarda chiliensis. Bonito are a small tuna, reaching no more than 11 kg (24 lbs) in weight. Uncommon in the Pacific Northwest, Pacific bonito are most likely to be found off of the coast of Washington. Their population is greatest around Central California but travels north when waters are warmer, reaching even British Columbia.
