First Report on the Use of the Larval Catcher Type Trawl Net for the Efficient Sampling of Juveniles of Two Tuna Species (<i>Thunnus orientalis</i> and <i>T. albacares</i>) in the Offshore Waters of the Nansei Islands, Japan

Establishing sampling techniques for juveniles of tuna species is essential understanding their ecology and population dynamics because only individuals showing rapid growth during larval juvenile stages are able to survive. This study the first report on successful using larva catcher (LC)-type trawl net, a pelagic gear with 10 × 10-m mouth opening, 40-m total length, 5 5-mm mesh size. It was used in research cruise May-June 2009. The LC net horizontally towed 30 min at depths 0 m-10 m speeds about 1.8 m/s. Overall, 66 163 Pacific bluefin (PBT) yellowfin (YFT) were collected; standard length (SL) PBT YFT ranged from 15.0 29.7 mm 11.7 34.8 mm, respectively. operation time trawls LC-type much shorter than that usual trawls; therefore, larger number operations can be conducted day. We concluded collecting its catchability ease operation.