Kindai University achieves complete aquaculture of the nodoguro fish: Aims to establish technology

The Aquaculture Research Institute at Kindai University (based in Shirahama Town, Wakayama Prefecture) has become the first in the world to achieve complete aquaculture of nodoguro (Blackthroat seaperch). This marks the 30th fish species to complete the full aquaculture cycle at the institute. Professor Keitaro Kato commented: "Since there have been almost no examples of research on nodoguro aquaculture, we want to develop the basic techniques—including rearing methods, feeding methods, and disease control—and establish stable seedling production technology. nodoguro takes longer to grow than yellowtail and similar fish, requiring three years to reach market size, but this achievement of complete aquaculture has opened the door to selective breeding."

nodoguro is a premium fish so rich in fat it is often called "the toro tuna belly of white-fleshed fish." Because it lives at depths of 100 to 600 meters, bringing it to the surface causes its eyes to bulge out, killing it. As a result, little has been known about its living conditions, and there have been almost no prior attempts at aquaculture.

Research at the institute's Toyama Station began in 2015. In 2016, eggs were successfully collected from nodoguro caught in Nyuzen Town, Toyama Prefecture, leading to successful artificial insemination and artificial hatching—but stable egg collection remained elusive. "Because fishing times and nodoguro spawning times don't align, we could barely collect any eggs," said Kato. In 2018, the institute asked Niigata Prefectural Kaiyo High School and the Joetsu Fisheries Cooperative for cooperation in egg collection and signed collaboration agreements with both. By adjusting fishing hours, stable egg collection became possible. In 2019, egg collection, artificial insemination, and artificial hatching from nodoguro caught off the Joetsu coast were all successful, with 200 individuals surviving to 50 days of age. In 2022, improved rearing techniques led to the production of approximately 10,000 seedlings, and in 2023, more than 30,000 seedlings were produced.

However, the Noto Peninsula Earthquake of January 1, 2024 damaged the facilities and killed some of the nodoguro. Technical Staff Member Naotaka Nakamura explained: "Some of the tanks and oxygen supply pipes were broken, and 3,000 of the 8,000 fish born in 2022 and 5,000 of the 20,000 born in 2023 died." He added: "As a way of expressing our gratitude to the fishers who helped us, we released 8,000 juvenile fish raised from eggs in 2024 and 37,000 in 2025."

In 2025, the nodoguro born in 2022 reached three years of age, so the institute was able to attempt complete aquaculture. In August, the water temperature was raised above 20℃ to encourage natural maturation, resulting in natural spawning—but no fertilization. From late September, hormone treatments were used to stimulate natural spawning, producing a total of approximately 200,000 eggs, but still without fertilization.

On October 4, eggs were collected through hormone-induced maturation (8 rounds from 6 females), yielding approximately 360,000 eggs. Artificial insemination followed, and on October 6, artificial hatching succeeded—completing the full aquaculture cycle. Currently, the institute is raising approximately 7,000 complete-aquaculture juvenile fish.

Kato commented: "Almost all of the artificially hatched nodoguro are male, with females accounting for only about 3%, so we want to advance research on rearing conditions and other methods to increase the proportion of females, in order to maintain a continuous supply of eggs."