The body fat of yellowfin tuna larvae has greatly increased after 8 months, which is close to the high commercial value of bluefin tuna skin oil.

Yellowfin tuna can also be made into sashimi, but of course it is not as expensive as bluefin tuna, and because it is caught all year round, it is a common source of sashimi in Taiwan. Yellowfin tuna are now caught by fishing boats, but yellowfin tuna can actually be farmed. The Aquatic Research Institute of the Council of Agriculture has just completed its four-year yellowfin tuna culture program. The aquaculture institute has analyzed the breeding effect along the offshore resources research center. In fact, yellowfin tuna fat has not lost the skin oil of bluefin tuna. The fat rate is nearly 8%, which is more than 15 times that of wild yellowfin tuna, and the culture time is only 8 months, which can not only reduce the cost of capital, but also avoid the breeding risk of typhoon season.

Wu Longjing, director of the Offshore Resources Research Center of the Water Test Institute, pointed out that the four-year plan is from 2014 to 2018. After young yellowfin tuna are caught at sea, they will be cultured in a cage net at sea for about three years. The size of the market can reach 36 kilograms, and the cost of bait during the feeding period of 300 yellowfin tuna is about NT $8 million. However, judging from the market value and consumer preference of yellowfin tuna, there is a lack of interest in yellowfin tuna farming.

But the researchers found that if you don't raise it to 36 kilograms, just raise it to 10 kilograms, which not only reduces the financial pressure, but also achieves the commodity effect, but it depends on the change of consumers' attitudes. According to research records, wild yellowfin tuna has a fat ratio of 0.2% when it is 50 cm long and 2.1 kg, and 0.4% when it is 136 cm long and 36 kg, so yellowfin tuna is a source of low-fat fish.

However, the situation of yellowfin tuna farmed in cage nets is completely different. Young yellowfin tuna are raised from 1.5 kilograms. After four months of fattening, they grow to 66.2 centimeters long and weigh 5.44 kilograms. The fat ratio is as high as 7.47%, which is more than 15 times that of 36 kg yellowfin tuna in the wild, and is higher than 3.99% of the lower abdomen of bluefin tuna sold in the market. This also highlights the commercial value of yellowfin tuna farmed in the fattening process.

The breeding report of the research center points out that the lipid content in the lower abdomen of bluefin tuna is 3.99%, which is the grade of sashimi priced at 1500 yuan per kilogram. If yellowfin tuna is raised for 12 months, the weight of each tail can reach 7 to 11 kilograms, and the fat content of yellowfin tuna can reach 20%. Moreover, the fat of yellowfin tuna is evenly distributed throughout the tail, which is very different from the fat proportion and price of bluefin tuna.

Wu Longjing believes that it is just right for yellowfin tuna cultured in cage nets to reach 10 kilograms, because it takes only eight months to raise young fish to 10 kilograms, and the fattening time of eight months is just enough to avoid the typhoon season. the cage culture is at sea, it is greatly affected by walruses, and it is common for the box net to be damaged by typhoons, so the fattening period of 8 months can avoid the risks caused by typhoons. The financial pressure of the operators is also relatively small.

Although farmers are not interested in cultivating yellowfin tuna yet, with the continuous strengthening of environmental protection and health awareness, yellowfin tuna may one day become one of the species farmed in marine cages. Why is it related to health? Because the worry about eating large migratory fish is that methylmercury will accumulate in the bodies of large fish at the top of the food chain, Wu Longjing said that the amount of methylmercury in the meat of farmed yellowfin tuna is much lower than that of wild yellowfin tuna. it is also much lower than the allowable value set by the Ministry of Health and Welfare.

Comparative data of fat ratio in yellowfin tuna culture experiment

Along the Offshore Resources Research Center, the Water Test Institute has set up a box net with a diameter of about 20 meters at a water depth of about 27 meters in the Hengchun sea area for yellowfin tuna culture. the test box net adopts a sinkable design, which can sink to more than 10 meters in the event of a typhoon.