TRANSPORTATION OF FERTILIZED EGGS OF PACIFIC BLUEFIN TUNA THUNNUS ORIENTALIS FROM SPAWNING SITE TO LARVAL PRODUCTION SITE IN FISHERIES LABORATORY, KINKI UNIVERSITY

摘要

Spawning water temperature of cultivated Pacific bluefm tuna (PBT) Thunnus orientalis ranges 25-29 deg C (Seoka et al., 2007). Stable water temperature in this range is also required for high reproductive performance (Miyashita, 2002). The Fisheries Laboratory, Kinki University (FLKU) has two spawning and larval production sites for cultivated PBT in Japan: Amami-Ohshima Island (28 deg 13.3'N 129 deg 12.5'E) in Kagoshima Prefecture and Kushimoto (33 deg 27.4'N 135 deg 47.1'E) in Wakayama Prefecture (Fig. 1). At the latter site, spontaneous spawning has not occurred every year due to low water temperature and/or large fluctuations in water temperature and salinity before/during the spawning season. When no spawning occurs at the Kushimoto site, we have to transport fertilized eggs from the Amami-Ohshima site for larval production as some experiments on PBT larviculture are carried out at this site; however, the most direct distance between the sites is 1,000 km. At the Amami-Ohshima site, PBT broodfish spawn eggs every year but at night time, around 21:00 h and PBT eggs hatch around 24h after fertilization. This limited time period between spawning and hatching makes the transportation of eggs complex. FLKU has developed various procedures for theegg transportation from the Amami-Oshima site to the Kushimoto site. In this presentation, we will show one of the fastest procedures among them.