It wasn’t until the 1980s that Americans discovered that all tuna didn’t come in a can. Since then, the popularity of fresh and frozen tuna especially yellowfin and bigeye has soared. Today, you can find fresh tuna at almost every good seafood restaurant and seafood counter around the country. Seared on a hot grill and served rare, it’s a sensational seafood.
 
With annual landings of more than 900,000 metric tons a year, yellowfin tuna is the most valuable tuna resource in the world. More than 60% of the yellowfin catch is caught by seiners, which brine freeze the catch and deliver it to tuna canneries. 
 
A truly global resource, yellowfin inhabit warm waters of the Atlantic, Pacific and Indian Oceans. The Mediterranean is the only warm sea where yellowfin are not fished commercially.
 
The Hawaiian name, ahi, refers to both yellowfin and bigeye tuna.
 “Burnt” tuna describes fish that lack a bright red meat color and have more watery, softer flesh. This condition is often associated with yellowfin caught near the surface of the ocean, often in handline or troll fisheries. Although burned tuna sells for a substantial discount because it cannot be served raw as sashimi, after it is cooked it is very acceptable.
 
Whether it’s caught off Ecuador, Hawaii or Bali, almost all of the true “sashimi-grade” fresh yellowfin and bigeye tuna is sold to Japanese buyers who pay a premium price.
 
Japan is the largest market for fresh and frozen tuna, consuming more than 200,000 tons a year. The U.S., on the other hand, consumes about 55,000 tons of fresh and frozen yellowfin and bigeye.
Ecuador exports more than 7,000 tons of fresh yellowfin and bigeye to the U.S. market a year, making it the single largest supplier. Trinidad is next with exports of about 4,000 tons a year.
 
Tuna longliners set their lines at night, fishing waters more than 1,000 feet deep, where larger fish are found. Lightsticks are attached to the line to attract bait fish and hence tuna. During periods of the full moon, fishing with lightsticks is less effective and most boats will deliver during this period, one reason tuna prices tend to be lowest at the full moon.
 
 “Clipper” is a term that is applied to the fleets of longline tuna boats that freeze their fish at -60°F for the Japanese sashimi market. Originally owned and operated by Japanese companies, most of the clipper boats are now operated by Korean, Taiwanese and Chinese companies.
 
California leads the U.S. in yellowfin catches, producing about 5,000 tons of fish a year, most of which is small fish which is canned. Louisiana is also a leading sources of fresh longline yellowfin. Hawaii is the only state that produces landings of both yellowfin and bigeye tuna. Catches in both Louisiana and Hawaii range between 1,000 to 2,000 tons a year. 
 
Yellowfin and bigeye are graded both by fat content and color, which can be an objective exercise, as standards can vary from supplier to supplier, depending both upon the experience of the grader and the condition of the market. Fish with the highest fat content and the brightest red bring a premium price. 
 
The amount of myoglobin in a tuna’s muscle determines its color. The more myoglobin, the redder the flesh. The amount of myoglobin is a function of a tuna’s age, physical activity and species. 
 
After the flesh of a tuna is exposed to air, an iron ion in the myoglobin molecule will start to oxidize, which turns the meat brown. For that reason, it is important to keep tuna loins and steaks wrapped in plastic. 
 
Until recently, frozen tuna had to be held at ultra cold temperatures such as -60°F to retard oxidation and prevent the meat from turning brown (brown frozen yellowfin is called “chocolate” tuna). However, exposing red tuna meat to tasteless smoke for up to 12 hours can fix the red color so that tuna held at conventional cold storage temperatures of 0 to -10°F will not turn brown. 
 
Some tuna suppliers use carbon monoxide (CO) to fix a frozen tuna’s red color. However, with CO the color can also be enhanced, allowing processors to make a lower grade of tuna appear higher than it is. The FDA requires that seafood exposed to either tasteless smoke or CO be labeled accordingly. 
Tuna that are not properly iced after catching and left in the sun can produce histamines. Although histamine poisoning is rarely fatal, it can be extremely uncomfortable.


Back