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Yellowtail Aquaculture Business Using Artificial Seedlings
"Kurose Yellowtail", a brand of farmed Yellowtail, is the product of maximum utilization of the Nissui Group network.


   

Yellowtail Aquaculture Business Using Artificial Seedlings

"Kurose Yellowtail," a brand of farmed Yellowtail, has met with favorable reception since its launch, due to its adequate amount of fat and the pleasant color of its chiai (deep red flesh near the spine).
Kurose Yellowtail is the product of maximum utilization of the Nissui Group network, which covers every process from the research and development of aquaculture technology and the development and production of feed to maintaining the freshness of fish and hygienic processing.

Home of Kurose Yellowtail along the Japan Current

At the core of the Nissui Group's Yellowtail aquaculture business is Kurose Suisan Co., Ltd. (Kushima City, Miyazaki Prefecture), a 100%-owned subsidiary of Nissui established in January 2004. As of April 1, 2012, Kurose Suisan has 160 employees and over 400 sink-and-float-type fish cages. Kurose Suisan ships 1.2 million Yellowtails per year, and assuming an average weight of 5 kg per fish, it is one of the nation's largest Yellowtail farming companies, responsible for approximately for 5% of all Yellowtail production in Japan.

The home of Kurose Yellowtail, which began shipment in May 2004, is Shibushi Bay in Miyazaki Prefecture. The coastal waters off of Shibushi are constantly washed by the Japan Current and are ideal for the farming of Yellowtail.

The farming of Kurose Yellowtail begins by catching wild mojako (young Yellowtail), which weigh a mere 2 grams. Every April and May, mojako spawned in the seas off Japan are carried by the Japan Current together with drifting seaweed to Shibushi Bay and the Hyuga-nada Sea. They are then caught by the fishermen's cooperatives of Kushima and Uchinoura (Kagoshima Prefecture) and brought to the calm and pristine waters of Shibushi Bay to be raised in the dedicated fish farms.

In fall, when the fish grow to about 1 kg, they are transported to the Kurose fish farm, located in the bay 3 km off the shore of Kushima, until they reach adulthood. The fish cages are 10-by-10 meters and 8 meters deep. The cages are sink-and-float-type fish cages, which are left submerged underwater at a depth of 8 to 10 meters and brought to the surface only for feeding.

By keeping the fish cages submerged underwater, damage caused by typhoons, rough seas, and direct sunlight can be avoided, in addition to reducing the amount of stress on the fish. As Yellowtail are naturally found in medium to deep waters, Kurose Suisan's fish cages, compared to regular fish cages, offer an environment that is closer to the fish's natural habitat.

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Summer is the best season for "Kurose Wakaburi" (2-years-old Yellowtail)

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Since June 2009, Kurose Suisan has been marketing its seasonal product, Kurose Wakaburi, which is intended for consumption in the summer.

The Kurose Wakaburi brand has been made possible through the development of artificial seedling technology, which involves the early collection of eggs from farmed broodstock. This early-collection artificial seedling technology was jointly developed by the Oita Marine Biological Technology Center of Nissui's Aquaculture Business Promotion Office (Saeki City, Oita Prefecture) and the Fisheries Research Agency using water tanks with control over photoperiods (length of light and dark periods) and water temperatures. This technology has made it possible to harvest 2-year-old fish with good flesh quality a few months earlier, and by mating these fish with the 2-year-old fish raised from large wild mojako, it is now possible to produce Yellowtail with good flesh quality even in the summer months.

As farmed Yellowtail, similarly to wild Yellowtail, lay their eggs during May and June when they are 3 years old, flesh quality tends to deteriorate due to the low fat content in the post-spawning summer season. By offering fish with good flesh quality even in the summer months, which has traditionally been the off-season for Yellowtail, Kurose Wakaburi has been well received by numerous customers such as sushi shops, restaurants and retailers, and is increasing summertime shipment. In other words, it is now possible to ship Yellowtail with consistent quality year-round.

In a sensory test conducted by Nissui comparing Kurose Wakaburi with post-spawning wild Yellowtail (3 years old), the 3-year-old fish were found to have a stronger acidic taste and fishier taste and scent under analysis items. Kurose Wakaburi, on the other hand, was found to have a good fat content. Under preference items as well, Kurose Wakaburi tended to be preferred overall. It is particularly noteworthy that the Kurose Wakaburi was preferred for its scent, taste and flavor.

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