Method lets more females enter the male-dominated farmed eel world
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NISHIO, Aichi Prefecture–Scientists here say a common food ingredient increases the chances of farmed eels becoming females, which are larger, softer and tastier than their more abundant male counterparts.
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The Aichi Fisheries Research Institute’s inland water fisheries research center said its technology will lead to a more effective use of natural resources and expand the supply of eels produced in Aichi Prefecture.
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For eel farming, elvers, or young eels, are caught in the wild, and their sex is determined in the maturing process, according to the center.
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Although the cause is not known, 90 percent or more of cultured eels become males.
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Male eels are often shipped when they reach 200 to 250 grams because their flesh and skin hardens as they grow, the researchers said.
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In contrast, female eels grow larger and have softer and tastier meat, researchers said.
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The research center in fiscal 2018 started studies on how to farm female eels more effectively. It took advantage of a conventional sex conversion method used to produce eggs for a complete eel culturing cycle.
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When food mixed with soy isoflavone, a substance found in soya products, was provided for the farmed eels, the center discovered 90 percent or more of them became female.
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“Eels can be brought up safely because a material deriving from foodstuffs we usually consume, such as tofu and natto, is used,” said a center representative.
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Nishio and other major farming areas in Aichi Prefecture produced 4,362 tons of eels in 2019, second only to Kagoshima Prefecture.
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Eel populations in the wild have plummeted, and the price for elvers over the last five years was triple to eightfold the cost from 10 years earlier.
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The Aichi prefectural government, working with Isshiki Unagi Gyogyo Kyodo Kumiai (Isshiki eel fisheries cooperative association) in Nishio, plans to start a verification test at a farming pool in fiscal 2021, which starts in April.
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Under the plan, the new method will become widely available for farming agents, and cultured female eels will be delivered to consumers starting in fiscal 2023.
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