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PubMed | National Research Institute of Aquaculture, Kagoshima Prefectural Fisheries Technology and Development Center, Nihon University, Chiba Prefectural Fisheries Research Center Freshwater Station and 3 more.
Type: Journal Article | Journal: PloS one | Year: 2015

Short-time tracking (one to eight days) of the Japanese eel (Anguilla japonica) using ultrasonic transmitter was performed in the tropical-subtropical area adjacent to the spawning area and temperate area off the Japanese Archipelago. Of 16 eels (11 wild and five farmed) used, 10 wild eels displayed clear diel vertical migration (DVM) from the beginning, while the other five farmed eels tracked for 19 to 66 hours did not. During daytime, a significantly positive correlation between migration depth and light intensity recorded on the vessel was observed in the 10 wild eels, indicating that the eels were sensitive to sunlight even at the middle to lower mesopelagic zone (500 to 800 m). During nighttime, the eel migration depth was observed to be associated with the phase, rising and setting of the moon, indicating that the eels were sensitive to moonlight at the upper mesopelagic zone (<300 m). Two of 10 wild eels were in the yellow stage but shared similar DVM with the silver stage eels. Swimbladders of three silver stage eels were punctured before releasing, but very little effect on DVM was observed. The eels very punctually initiated descent upon nautical dawn and ascent upon sunset, enabling us to determine local times for sunrise and sunset, and hence this behavior may be used for geolocating eels. In fact, estimated positions of eels based on the depth trajectory data were comparable or even better than those obtained by light-based archival tag in other fish species.


PubMed | Japan National Research Institute of Fisheries Science, Kagoshima Prefectural Fisheries Technology and Development Center, Kumamoto Prefectural Fisheries Research Center and Kaneka Corporation
Type: | Journal: Harmful algae | Year: 2016

In this study, the Kaneka DNA chromatography chip (KDCC) for the Alexandrium species was successfully developed for simultaneous detection of five Alexandrium species. This method utilizes a DNA-DNA hybridization technology. In the PCR process, specifically designed tagged-primers are used, i.e. a forward primer consisting of a tag domain, which can conjugate with gold nanocolloids on the chip, and a primer domain, which can anneal/amplify the target sequence. However, the reverse primer consists of a tag domain, which can hybridize to the solid-phased capture probe on the chip, and a primer domain, which can anneal/amplify the target sequence. As a result, a red line that originates from gold nanocolloids appears as a positive signal on the chip, and the amplicon is detected visually by the naked eye. This technique is simple, because it is possible to visually detect the target species soon after (<5min) the application of 2L of PCR amplicon and 65L of development buffer to the sample pad of the chip. Further, this technique is relatively inexpensive and does not require expensive laboratory equipment, such as real-time Q-PCR machines or DNA microarray detectors, but a thermal cycler. Regarding the detection limit of KDCC for the five Alexandrium species, it varied among species and it was <0.1-10pg and equivalent to 5-500 copies of rRNA genes, indicating that the technique is sensitive enough for practical use to detect several cells of the target species from 1L of seawater. The detection sensitivity of KDCC was also evaluated with two different techniques, i.e. a multiplex-PCR and a digital DNA hybridization by digital DNA chip analyzer (DDCA), using natural plankton assemblages. There was no significant difference in the detection sensitivity among the three techniques, suggesting KDCC can be readily used to monitor the HAB species.


Tanaka T.,Kagoshima Prefectural Fisheries Technology and Development Center | Yoshimitsu S.,Kagoshima Prefectural Fisheries Technology and Development Center | Imayoshi Y.,Kagoshima Prefectural Fisheries Technology and Development Center | Ishiga Y.,Kagoshima University | Terada R.,Kagoshima University
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2013

Distributions of seaweed/seagrass communities were determined from 230 sites along the coast of Kagoshima Bay, southern Japan, during a series of surveys in 2006. Sargassum (brown algae) and Zostera (angiosperm) communities were confirmed from 159 and 41 sites, respectively. Of the 19 species of Sargassum and Zostera confirmed in this study, distributional characteristics of 12 major species were also elucidated. Kagoshima Bay is comprised of three different areas (back, central part and mouth of the bay) as defined by the influence of waters entering the bay from the Kuroshio Current. Two Zostera species, Z. marina and Z. japonica, and four temperate species of Sargassum, S. fusiforme, S. hemiphyllum, S. patens, and S. piluliferum, were confirmed from all areas. Meanwhile, six subtropical and warm-temperate species, S. alternatopinnatum, S. crispifolium, S. cristaefolium, S. duplicatum, S. glaucescens, and S. incanum, were not detected in Kagoshima Bay except for some sites, as indicated by a previous survey in 1976; however, we detected them from various sites in the central part and mouth of the bay. We suggest that these species appeared and developed communities in the past 30 years.


Watanabe Y.,Kagoshima University | Nishihara G.N.,Nagasaki University | Tokunaga S.,Kagoshima Prefectural Fisheries Technology and Development Center | Terada R.,Kagoshima University
Journal of Applied Phycology | Year: 2014

Phenology, irradiance, and temperature characteristics of an edible brown alga, Undaria pinnatifida (Laminariales), were examined from the southernmost natural population in Japan, both by culturing gametophytes and examining the photosynthetic activity of sporophytes using dissolved oxygen sensors and pulse amplitude-modulated chlorophyll fluorometer (IMAGING-PAM). Our surveys confirmed that sporophytes were present between winter and early summer, but absent by July. IMAGING-PAM experiments were used to measure maximum effective quantum yield (ΦII at 0 μmol photons m-2 s-1) for each of 14 temperatures (8-36 °C). Oxygen production was also determined over a coarser temperature gradient. Net photosynthesis and ΦII (at 0 μmol photons m-2 s-1) were observed to be temperature-dependent; the maximum ΦII was estimated to be 0.67, occurred at 21.2 °C, and was nearly identical to the optimal temperature of the net photosynthetic rate (21.7 °C). A net photosynthesis-irradiance (P-E) model revealed that saturation irradiance (Ek) was 119.5 μmol photons m-1 s-1, and the compensation irradiance (Ec) was 17.4 μmol photons m-1 s-1. Culture experiments on the gametophytes revealed that most individuals could not survive temperatures over 28 °C and that growth rates were severely inhibited. Based on our observations, temperatures greater than 20 °C are likely to influence photosynthetic activity and gametophyte survival, and therefore, it is possible that this species might become locally extinct if seawater temperatures in this region continue to rise. © 2014 Springer Science+Business Media Dordrecht.


Watanabe Y.,Kagoshima University | Nishihara G.N.,Nagasaki University | Tokunaga S.,Kagoshima Prefectural Fisheries Technology and Development Center | Terada R.,Kagoshima University
Phycological Research | Year: 2014

The effect of irradiance and temperature on the photosynthesis of the red alga, Pyropia tenera, was determined for maricultured gametophytes and sporophytes collected from a region that is known as one of the southern limits of its distribution in Japan. Macroscopic gametophytes were examined using both pulse-amplitude modulated fluorometry and/or dissolved oxygen sensors. A model of the net photosynthesis-irradiance (P-E) relationship of the gametophytes at 12°C revealed that the net photosynthetic rate quickly increased at irradiances below the estimated saturation irradiance of 46μmol photons m-2s-1, and the compensation irradiance was 9μmol photons m-2s-1. Gross photosynthesis and dark respiration for the gametophytes were also determined over a range of temperatures (8-34°C), revealing that the gross photosynthetic rates of 46.3μmol O2 mgchl-a-1min-1 was highest at 9.3 (95% Bayesian credible interval (BCI): 2.3-14.5)°C, and the dark respiration rate increased at a rate of 0.93μmol O2 mgchl-a-1min-1°C-1. The measured dark respiration rates ranged from -0.06μmol O2 mgchl-a-1min-1 at 6°C to -25.2μmol O2 mgchl-a-1min-1 at 34°C. The highest value of the maximum quantum yield (Fv/Fm) for the gametophytes occurred at 22.4 (BCI: 21.5-23.3) °C and was 0.48 (BCI: 0.475-0.486), although those of the sporophyte occurred at 12.9 (BCI: 7.4-15.1) °C and was 0.52 (BCI: 0.506-0.544). This species may be considered well-adapted to the current range of seawater temperatures in this region. However, since the gametophytes have such a low temperature requirement, they are most likely close to their tolerable temperatures in the natural environment. © 2014 Japanese Society of Phycology.


Hamasaki K.,Tokyo University of Marine Science and Technology | Toriya S.,Tokyo University of Marine Science and Technology | Shishidou H.,Kagoshima Prefectural Fisheries Technology and Development Center | Sugaya T.,Japan National Research Institute of Fisheries Science | Kitada S.,Tokyo University of Marine Science and Technology
Journal of Fish Biology | Year: 2010

Variation in the mitochondrial DNA transcriptional control region sequence was investigated in wild and hatchery-released red sea bream Pagrus major from Kagoshima Bay, where an extensive hatchery-release programme has been conducted for >30 years. The programme has successfully augmented commercial catches in the bay (released juveniles have been produced from the captive broodstock, repeatedly used over multiple generations). Samples were also obtained from outside the bay, where limited stocking has occurred. Genetic diversity indices measured as number of haplotypes, haplotype richness, haplotype diversity and nucleotide diversity were lower in hatchery-released fish than in wild fish. Genetic differences in wild fish from the bay, especially in the inner bay, compared with fish from outside the bay were detected in terms of decreased genetic diversity indices and changed haplotype frequencies. Unbiased population pair-wise FST estimates based on an empirical Bayesian method, however, revealed low genetic differentiation between samples from the bay and its vicinity. Mixed stock identification analyses estimated the proportion of hatchery-released fish in wild populations in the inner and central bays at 39·0 and 8·7%, respectively, although the precision of the estimates was very low because of the small genetic differentiation between populations and relatively small sample sizes. Hence, the long-term extensive hatchery release programme has affected the genetic diversity of wild populations in the bay; however, the genetic effects were low and appeared to remain within the bay. © 2010 The Authors. Journal of Fish Biology © 2010 The Fisheries Society of the British Isles.


Kawamata S.,Japan National Research Institute of Fisheries Engineering | Yoshimitsu S.,Kagoshima Prefectural Fisheries Technology and Development Center | Tokunaga S.,Kagoshima Prefectural Fisheries Technology and Development Center | Kubo S.,Kagoshima Prefectural Fisheries Technology and Development Center | Tanaka T.,Kagoshima Prefectural Fisheries Technology and Development Center
Marine Biology | Year: 2012

Although sediment deposition has detrimental effects on macroalgal settlement and recruitment, fucoid algae (mainly Sargassum duplicatum) thrive on rocky reefs always overlaid with fine sediments in sheltered sites of Kagoshima, Japan. The aim of the present study was to assess their ability to settle and recruit onto sediment-covered substrata. A transplant experiment using boulders with Sargassum juveniles attached showed that the 30-day survival rate was as high as 50% even for the juvenile stage (<10 mm) on boulders completely buried with sediment. In addition, an outdoor tank experiment testing the effects of different sediment thicknesses (0-4 mm) on already settled 4-day old S. duplicatum germlings indicated significant reductions in growth by the presence of sediment cover even at 0.5 mm but no significant increase in mortality up to 2 mm. Furthermore, an in situ experiment in which sterilized cobbles were placed at a sediment-covered site to allow sediment to settle over them before the embryo release showed a uniformly high recruitment of Sargassum over the cobbles. This suggests the presence of unknown mechanisms to allow the settlement of propagules on substrata thinly but completely covered by fine sediments. © 2011 Springer-Verlag.


Kawamata S.,Japan National Research Institute of Fisheries Engineering | Yoshimitsu S.,Kagoshima Prefectural Fisheries Technology and Development Center | Tanaka T.,Kagoshima Prefectural Fisheries Technology and Development Center | Igari T.,Kagoshima Prefectural Fisheries Technology and Development Center | Tokunaga S.,Kagoshima Prefectural Fisheries Technology and Development Center
Journal of Sea Research | Year: 2011

Sedimentation can provide indirect benefits to the survival of macroalgae in areas with potentially high grazing pressure. Field studies were performed in an embayment with extensive urchin barrens but also with locally persistent fucoid beds, on the coast of Kagoshima, south-western Japan, to elucidate the physical and biological processes responsible for the maintenance of the beds. Rocky subtidal reefs devoid of fine sediment were almost completely barren and dominated by sea urchins (primarily Echinometra sp. A), while fucoid algae (predominantly Sargassum duplicatum) densely populated cobble sites overlaid with a thin layer of fine sediment (medium grain size: 0.15-0.25. mm). Quadrat samplings in areas intermixed with urchin barrens and sand flats as well as experimental addition of sediment suggested that Echinometra sp. was readily excluded from hard substratum overlaid with even only a thin layer of fine sediment. Quadrat surveys and a transplant experiment conducted at the border area between a cobble bed with a thin cover of fine sediment and a sediment-free boulder one indicated that sea urchins (mainly composed of Echinometra sp. and Diadema spp.) rarely invaded the sediment-covered bed to graze. Wave measurements at the entrance (8. m deep) of the embayment over a 3.5-year period showed that the study area had long-term extremely calm conditions (84% of significant wave heights < 0.1. m) and seasonal or transient moderate disturbances due to relatively high waves (significant wave height: 0.8-1.3. m). However, the 2-year time series of root-mean-square wave orbital velocity estimates at different sites consistently suggested that the wave-action intensities at urchin barrens were still too high for deposition of fine sediments which occurred in more wave-sheltered persistent fucoid area. Nearly 2-year investigations on sediment level change and on cobble substrates together with overlying sediment in the fucoid area suggested that the absence of fatal sediment inundation and maintenance of the thin overlying sediment layer (mean thickness < ca 2. mm) throughout the year allowed settlement and growth of sand-tolerant fucoids by preventing urchin grazing. © 2011 Elsevier B.V.


Ashida H.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Horie M.,Kagoshima Prefectural Fisheries Technology and Development Center
Fisheries Science | Year: 2015

To illustrate the spawning characteristics of skipjack tuna Katsuwonus pelamis in the Northwestern Pacific Ocean, we examined seasonal changes in the histological condition of gonads, spawning fraction, and batch fecundity (BF) of skipjack tuna caught around Amami-Oshima in the northern Nansei Islands, Japan, from May 2011 to July 2013. Females classified as “mature” appeared from June to October, and mature males were present from April to November. Spawning began in June when the sea surface temperature (SST) exceeded 24 °C and peaked in August. Although the SST was still above 24 °C, spawning ended in September when the SST started decreasing continuously. The minimum size (fork length, FL) at first maturity was 40.5 cm for females and 37.6 cm for males. The BF (mean ± SD) and relative batch fecundity (RBF) were estimated at 93,700 ± 21,800 oocytes and 56.8 ± 14.3 oocytes/g, respectively. The total spawning fraction (spawning intervals) during the spawning season was estimated at 0.53 (1.88 days). These results indicate that the spawning activity of skipjack tuna around Amami-Oshima changes seasonally depending on SST. © 2015, Japanese Society of Fisheries Science.


Miwa S.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Kamaishi T.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Hirae T.,Kagoshima Prefectural Fisheries Technology and Development Center | Murase T.,Kagoshima Prefectural Fisheries Technology and Development Center | Nishioka T.,Japan National Research Institute of Fisheries And Environment of Inland Sea
Journal of Fish Diseases | Year: 2011

An outbreak of a disease characterized by a peculiar spiral movement in farmed greater amberjack, Seriola dumerili (Risso), occurred in Kagoshima Prefecture, Japan, in May 2008, immediately after importing the fish from China. Although neither bacteria nor viruses were detected in routine diagnostic tests, histopathological observations of the affected fish revealed severe inflammation in the tegmentum of the brain including the medulla oblongata and the anterior part of the spinal cord. In addition, a microsporidian parasite was observed in the nerve cell bodies or axons in the inflamed tissues. We identified a microsporidian small subunit rRNA gene (SSU rDNA) from the lesion, and the sequence showed 96.1% identity with that of Spraguea lophii. Subsequent in situ hybridization using probes presumably specific to the SSU rRNA confirmed that the parasite observed in histopathology harboured the identified SSU rRNA. Apparently degenerated microsporidian cells or spores were also frequently observed in tissue sections. Thus, the disease was most probably caused by the infection of a hitherto unknown microsporidian parasite that has a genetic affinity to the genus Spraguea, in the central nervous system of the amberjack. © 2011 Blackwell Publishing Ltd.

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