Press Release

July 26 , 2013

Incorporated Administrative Agency, Fisheries Research Agency

Success of advanced seed-production techniques in yellowtail fingerlings for aquaculture
- A new approach to prevent from harmful red tide damages to yellowtail aquaculture -

  • SNFRI succeeded in rearing broodstock in yellowtail matures half a year earlier than ordinal spawning period controlling environmental conditions. This technology allowed acquiring fertilized eggs of the fish in November 2011.
  • Using the eggs, SNFRI succeeded in producing much bigger cultured fingerlings of 15-20 cm size in sea cages of warm waters in Tanegashima Island than natural collected juveniles of 5-10 cm on April in 2012.
  • These techniques in yellowtail fingerlings enabled to ship the grown fish before second-year harmful red tide damages.

In Japan, yellowtail aquaculture usually starts in early summer using natural juveniles collected from costal sea areas. About two years later in autumn, they grow up in commercial size and are shipped out to the market. However, summer season just before the shipping overlaps with harmful red tide bloom period which sometimes causes serious damages to finfish aquaculture. Generally one-year yellowtail shows low susceptibility to red tides, however, two-year individuals are severely affected by second-year red tide. Therefore, the fisheries industrial association of yellowtail aquaculturists has been urgently in need of early shipment techniques for yellowtail fingerlings prevent from second-year harmful red tide damages.

Seikai National Fisheries Research Institute (SNFRI), Fisheries Research Agency, succeeded in collecting eggs from reared yellowtail broodstock on November, half a year earlier than usual spawning period of the fish, under the manipulated environmental rearing conditions (water temperature and photoperiod) in 2011. SNFRI also succeeded in growing up the fingerlings to 12 cm in total length by using collected fertilized eggs on March in 2012 (Fig.1).

These fingerlings were transported from SNFRI to Tanegashima Island where sea water temperature is higher than SNFRI area. The fish were cultured until middle April in 2012 in sea cages up to 20 cm in total length, the size is much bigger than natural juveniles, 5-10 cm, of the same season. Then they were transported and cultured at Azuma-Cho Fisheries Cooperative in Kagoshima Prefecture for over a year. Late July in 2013, the fish grew up to commercial size of 4 kg over. These early culture techniques in yellowtail fingerlings mentioned above is the first approach in Japan.

A research project commissioned by Agriculture, Forestry and Fisheries Research Council is now developing stable and low-cost early production techniques in the species, and SNFRI also continues to improve profitability and to establish mass production system to supply yellowtail fingerlings at an industrial level.

Picture: Natural collected juveniles (above), and cultured fingerlings (below) on April 2012 in Tanegashima Island in Kagoshima Prefecture.