caa a22 4500 606227652 CHVBK 20210128101159.0 cr unu---uuuuu 210128e20150401xx s 000 0 eng 10.1007/s10641-014-0350-8 doi (NATIONALLICENCE)springer-10.1007/s10641-014-0350-8 Reproductive condition, batch fecundity, and spawning fraction of large Pacific bluefin tuna Thunnus orientalis landed at Ishigaki Island, Okinawa, Japan [Elektronische Daten] [Hiroshi Ashida, Nobuaki Suzuki, Toshiyuki Tanabe, Nobuhiro Suzuki, Yoshimasa Aonuma] In order to illustrate the reproductive activity of Pacific bluefin tuna (Thunnus orientalis) around the Yaeyama archipelago, an area known to be the species' major spawning ground, gonadal condition of large individuals obtained by longline fishing was assessed during the commercial fishery season between late April and early July in 2008 and 2009. Almost all of the specimens landed at Ishigaki Island during these two seasons were larger than 200cm in fork length (FL), and, while the sex ratio was nearly 1:1 in total, a significant bias existed towards males when only individuals with FL values greater than 230cm were considered. All females were sexually mature and sperm was observed in the testes of all males throughout the fishing season. Average spawning intervals (fraction) and average batch fecundity (mean ± SD) were estimated at 3.29days (0.30) and 15.4 ± 10.2 million oocytes, respectively. Ovarian and testicular maturation phase based on histological assessment did not show any significant changes over the two-year study period, while commencement of spawning varied from year to year. We determined that spawning activity of Pacific bluefin tuna around the Yaeyama archipelago persisted throughout the fishing season, and likely varied due to the annual fluctuations in environmental conditions at the spawning ground. Springer Science+Business Media Dordrecht, 2014 Atresia nationallicence Germinal epithelium nationallicence Ovary nationallicence Spawning omission nationallicence Testis nationallicence Ashida Hiroshi Graduate School of Bioscience, Tokai University, 3-20-1 Orido, 424-8610, Shimizu, Shizuoka, Japan aut Suzuki Nobuaki Research Center for Subtropical Fisheries, Seikai National Fisheries Research Institute, Fisheries Research Agency, 148-446 Fukai-Ohta, 907-0451, Ishigaki, Okinawa, Japan aut Tanabe Toshiyuki National Research Institute of Far Seas Fisheries, Fisheries Research Agency, 5-7-1 Orido, 424-8633, Shimizu, Shizuoka, Japan aut Suzuki Nobuhiro Graduate School of Bioscience, Tokai University, 3-20-1 Orido, 424-8610, Shimizu, Shizuoka, Japan aut Aonuma Yoshimasa Research Center for Subtropical Fisheries, Seikai National Fisheries Research Institute, Fisheries Research Agency, 148-446 Fukai-Ohta, 907-0451, Ishigaki, Okinawa, Japan aut Environmental Biology of Fishes Springer Netherlands 98/4(2015-04-01), 1173-1183 0378-1909 98:4<1173 2015 98 10641 https://doi.org/10.1007/s10641-014-0350-8 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10641-014-0350-8 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ashida Hiroshi Graduate School of Bioscience, Tokai University, 3-20-1 Orido, 424-8610, Shimizu, Shizuoka, Japan aut NATIONALLICENCE 700 1- Suzuki Nobuaki Research Center for Subtropical Fisheries, Seikai National Fisheries Research Institute, Fisheries Research Agency, 148-446 Fukai-Ohta, 907-0451, Ishigaki, Okinawa, Japan aut NATIONALLICENCE 700 1- Tanabe Toshiyuki National Research Institute of Far Seas Fisheries, Fisheries Research Agency, 5-7-1 Orido, 424-8633, Shimizu, Shizuoka, Japan aut NATIONALLICENCE 700 1- Suzuki Nobuhiro Graduate School of Bioscience, Tokai University, 3-20-1 Orido, 424-8610, Shimizu, Shizuoka, Japan aut NATIONALLICENCE 700 1- Aonuma Yoshimasa Research Center for Subtropical Fisheries, Seikai National Fisheries Research Institute, Fisheries Research Agency, 148-446 Fukai-Ohta, 907-0451, Ishigaki, Okinawa, Japan aut NATIONALLICENCE 773 0- Environmental Biology of Fishes Springer Netherlands 98/4(2015-04-01), 1173-1183 0378-1909 98:4<1173 2015 98 10641