Shimode S.,University of Tokyo |
Takahashi K.,University of Tokyo |
Shimizu Y.,Tohoku National Fisheries Research Institute |
Nonomura T.,Tottori Prefectural Fisheries Experimental Station |
Tsuda A.,University of Tokyo
Progress in Oceanography | Year: 2012
We investigated the geographical and vertical distribution of the copepodid stages of Eucalanus californicus in the northwestern (NW) Pacific Ocean, and compared life history characteristics against the northeastern (NE) population of the species and the neighboring subarctic sister species, Eucalanus bungii. In the NW Pacific, multi-layered zooplankton samples were collected between 15°N and 49°N. High abundances (>1000inds. m -2) of E. californicus were restricted to an area around 33°N, whereas E. bungii was highly abundant between 36°N and 49°N. The occurrence of E. californicus in the surface layer was associated with seasonal spring ontogenetic vertical migration (OVM), as suggested by previous studies in the NE Pacific. Gonadal analysis of adult females showed that surface reproduction occurs during the spring in the slope water area, which is a region on the continental slope north of the Kuroshio axis, and within the Kuroshio-Oyashio Transition Area (TA). The seasonal OVM strategy of E. californicus in the NW Pacific is characterized by (1) shorter periods of surface reproduction and growth and (2) deep C5 stage dormancy (500-2000m). The former is an adaptive response to relatively high water temperatures and short bloom periods in the TA and slope water area. The latter strategy of deep dormancy is considered to be an adaptation to avoid drift caused by a local oceanic feature of deeper westward (>1000m) recirculation currents, thus retaining the population within the high primary production zones of the TA and slope water area. © 2011 Elsevier Ltd.
Onitsuka G.,Japan National Research Institute of Fisheries Science |
Miyahara K.,Hyogo Prefectural Institute of Technology |
Hirose N.,Kyushu University |
Watanabe S.,Tottori Prefectural Fisheries Experimental Station |
And 5 more authors.
Harmful Algae | Year: 2010
Since 2002, blooms of the harmful dinoflagellate Cochlodinium polykrikoides Margalef have occurred in the eastern San-in area, the Japanese coastal area fronting the southwest Sea of Japan. To investigate the occurrence mechanisms of the blooms, numerical experiments were conducted using a Lagrangian particle-tracking model, under different hydrographic conditions in 2002-2008. The results of Lagrangian simulations revealed that the source region of the blooms was located in the southeast Korean coastal area, >500 km away from the eastern San-in area. They were transported by the Tsushima Warm Current over about two weeks to one month. The blooms in the eastern San-in area were thought to occur only when a series of sequential conditions were met, which included preceding outbreaks in Korean waters, southwesterly winds in the Tsushima Strait, and the nearshore position of the Tsushima Warm Current off the San-in coast, veering eastward from the Korean peninsula. © 2010 Elsevier B.V. All rights reserved.
Tange N.,Tottori Prefectural Fisheries Experimental Station |
Song J.-Y.,Ehime University |
Kitamura S.-I.,Ehime University
Fish Pathology | Year: 2010
We designed a PCR primer set for specific detection of Miamiensis avidus causing scuticociliatosis in Japanese flounder Paralichthys olivaceus. In the PCR targeting the small subunit ribosomal RNA gene of M. avidus, the expected PCR product with 1,433 bp was amplified from four isolates of M. avidus including three different serotypes, but not from other scuticociliates including Pseudocohnilembus persalinus, P. hargisi and Uronema marinum. Detection limit of the present PCR was 125 fg of genomic DNA. When a group of Japanese flounder suffering the disease was examined by the PCR, 90% of symptomatic fish and 50% of asymptomatic fish were found positive. Thus it is considered that the PCR is useful for detection and identification of M. avidus and consequently for diagnosis of scuticociliatosis in Japanese flounder. © 2010 The Japanese Society of Fish Pathology.
Nakamura M.,Kyushu University |
Koterayama W.,Kyushu University |
Masuda S.,Tottori Prefectural Fisheries Experimental Station |
Miyabe S.,Tottori Prefectural Government Kansai Office |
Aso H.,Zeni Lite Buoy Co.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2012
The paper summarizes the design concept and outline of a buoy system for monitoring a coastal sea state. Miniaturization of the buoy was achieved by submerging it in severe sea conditions. The configurations and tensions of the mooring lines in disturbances were calculated, and it was confirmed that the design concept can be realized. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).
Fujino T.,Japan National Research Institute of Fisheries And Environment of Inland Sea |
Goto T.,Japan National Research Institute of Fisheries And Environment of Inland Sea |
Shimura T.,Tottori Prefectural Fisheries Experimental Station |
Yasuma H.,Hokkaido University |
And 4 more authors.
Journal of Marine Science and Technology (Taiwan) | Year: 2013
Egg abundance of Maurolicus japonicus, a dominant mesopelagic fish in the Japan Sea, was analyzed during 1981-2005 as an index of the spawning-adult abundance. There was a major change in egg abundance around 1988/1989, with negative anomalies occurring during 1981-1988 and positive anomalies occurring from l989. At about the same time (1986/1987), the Tsushima Current shifted from cold to warm conditions. Environmental indices were found to be positively correlated with egg abundance two years later. Our results suggest that the abundance of M. japonicus is affected by climatic regime shifts, and that it could be used as an indicator species.