Fukuoka Fisheries and Marine Technology Research Center

Nishi-Tokyo-shi, Japan

Fukuoka Fisheries and Marine Technology Research Center

Nishi-Tokyo-shi, Japan

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Qiu X.,Kyushu University | Yamasaki Y.,National Fisheries University | Shimasaki Y.,Kyushu University | Gunjikake H.,Kyushu University | And 7 more authors.
Thalassas | Year: 2011

We investigated growth interactions between the raphidophytes Chattonella antiqua (Hada) Ono and Heterosigma akashiwo (Hada) Hada ex Hara et Chihara using bi-algal cultures under axenic conditions. The growth of C. antiqua and H. akashiwo each tended to be strongly suppressed when the other species reached early stationary phase. A mathematical model was used to simulate the growth interactions of C. antiqua and H. akashiwo in bi-algal cultures. The model showed that C. antiqua outcompetes H. akashiwo over time in bi-algal cultures under all experimental conditions. Furthermore, despite re-enrichment with nutrients, the filtrate from dense cultures of C. antiqua reduced the maximum growth rate of H. akashiwo and filtrate from dense cultures of H. akashiwo reduced both the maximum growth rate and maximum yield of C. antiqua.


Qiu X.,Kyushu University | Yamasaki Y.,National Fisheries University | Shimasaki Y.,Kyushu University | Gunjikake H.,Kyushu University | And 8 more authors.
Marine Ecology Progress Series | Year: 2012

Growth interactions between the raphidophyte Heterosigma akashiwo and the dinoflagellate Akashiwo sanguinea were examined by using bi-algal culture experiments under axenic conditions. There was a lethal effect of H. akashiwo (initial cell density: 1 × 10 2 or 1 × 10 4 cells ml -1) on A. sanguinea at an initial cell density of 1 × 10 2 cells ml -1. Growth of both species was suppressed concurrently when initial cell densities of H. akashiwo and A. sanguinea were 1 × 10 2 and 2 × 10 3 cells ml -1, respectively. A mathematical model was used to simulate growth and interactions in bi-algal cultures. The model predicted that H. akashiwo would outcompete A. sanguinea over time. A cell-free enriched filtrate prepared from dense culture of H. akashiwo reduced both maximum growth rate and maximum yield of A. sanguinea. A filtrate of A. sanguinea prepared in the same manner only reduced maximum yield of H. akashiwo but did not affect its maximum growth rate. Growth of A. sanguinea in bi-algal cultures under contact conditions was significantly lower than that in mono-algal culture and in bi-algal cultures under noncontact conditions. Morphologically abnormal A. sanguinea cells occurred at high frequency only when A. sanguinea was cultured together with H. akashiwo under direct cell contact condition. Moreover, growth inhibition and formation of morphologically abnormal cells of A. sanguinea were induced in a concentration-dependent manner by allelochemicals (including allelochemical polysaccharide-protein complexes) produced by H. akashiwo. These results suggest that growth inhibition effects, via allelochemicals and direct cell contact by Heterosigma akashiwo, influence bloom formation of Akashiwo sanguinea in the field. © 2012 Inter-Research.


Qiu X.,Kyushu University | Yamasaki Y.,National Fisheries University | Shimasaki Y.,Kyushu University | Gunjikake H.,Kyushu University | And 6 more authors.
Harmful Algae | Year: 2011

We investigated the growth interactions between the raphidophyte Chattonella antiqua and the dinoflagellate Akashiwo sanguinea by using bi-algal cultures under axenic conditions. When initial cell densities of C. antiqua and A. sanguinea both were 1×102 cells ml-1, C. antiqua grew faster and its growth inhibitory effect on A. sanguinea was stronger than that of A. sanguinea on C. antiqua. In other combinations of inoculation densities, the species that was inoculated at lower cell density (1×102 cells ml-1) stopped growing soon after the start of the experiments, and cell density of this species gradually decreased after the other species reached early stationary phase. The mathematical model used to simulate the growth and interactions between the two species predicts that C. antiqua and A. sanguinea will approach an unstable equilibrium point of about 2.16×104 cells ml-1 (C. antiqua) and 1.46×104 cells ml-1 (A. sanguinea). Thus, one of the species always inhibits the growth of the other and their initial cell densities are critical in determining the successful species in growth competition. When one of these two species was inoculated at the cell density of 2×103 cells ml-1 in bi-algal culture experiments under noncontact and contact conditions, its growth inhibitory effect toward the other species was greater under contact conditions than under noncontact conditions. Furthermore, enriched filtrate from dense culture of C. antiqua resulted in both reduced maximum yield and maximum growth rate of A. sanguinea, whereas that of A. sanguinea resulted only in reduced maximum yield of C. antiqua but did not affect its growth rate. © 2011 Elsevier B.V.


Umino T.,Hiroshima University | Ueno K.,Hiroshima University | Mihara T.,Hiroshima University | Koike M.,Chugoku Branch | And 3 more authors.
Conservation Genetics Resources | Year: 2013

Small-scale sillago, (Sillago parvisquamis) form the basis of a traditional recreational fishery in Japan. Historically distributed across a wide range, this species is now limited to a single population in the southwest region of the Suonada Sound in the Seto Inland Sea, Japan. Eleven candidate microsatellite loci were isolated from a small insert genomic DNA library of S. parvisquamis. In a screen of 40 individuals from Buzen Sea, we identified polymorphisms at all loci with levels of variability ranging from 2 to 20 alleles with no evidence of linkage disequilibrium. Observed heterozygosities ranged from 0.45 to 0.95, with no locus exhibiting significant departure from Hardy-Weinberg equilibrium. A test for cross-amplification with Sillago japonica revealed a subset of seven polymorphic loci that were successfully amplified. The polymorphic microsatellite loci developed in the current study will facilitate conservation genetic studies in both species, particularly the endangered S. parvisquamis. © 2013 Springer Science+Business Media Dordrecht.


Yamaguchi Y.,Fukuoka Women's University | Noda K.,Fukuoka Women's University | Fujii T.,Fukuoka Women's University | Shinohara N.,Fukuoka Fisheries and Marine Technology Research Center | And 3 more authors.
Journal of Food Composition and Analysis | Year: 2011

This study aimed to elucidate the relationship between the chemical composition and the growth of a marine alga, Sargassum horneri (Turner) C. Agardh (abbreviated as S. horneri) harvested from the Chikuzen Sea, Fukuoka, Japan, as well as the changes in the chemical composition during pre-heating of harvested S. horneri. Both its length and weight reached maximum levels late in March. The mean chemical composition of S. horneri from December 2004 to May 2005 was 87.7% moisture, 1.0% protein, 0.1% lipid, 3.4% ash and 5.7% total dietary fiber. The ash contents of the male plants were higher in February but lower in March and April than those of the female plants. The lipid contents of the males were higher in March than those of the female plants. The protein content reached its maximum in February. The total dietary fiber content began to increase in February and reached its maximum at the end of March. The total dietary fiber content increased after full growth and maturity. S. horneri is a potential source of dietary fiber and minerals as a food ingredient. © 2011 Elsevier Inc.


Tezuka N.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Kamimura S.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Kamimura S.,Japan National Institute for Land and Infrastructure Management | Hamaguchi M.,Japan National Research Institute of Fisheries And Environment of Inland Sea | And 7 more authors.
Journal of Sea Research | Year: 2012

Although fluctuation and decline in bivalve populations have been reported worldwide, the underlying processes are not yet fully understood. This lack of understanding is partly due to an absence of demographic information for the early post-settlement period. This is the case particularly for annual production of the asari clam (also commonly known as the Manila clam, Ruditapes philippinarum) in Japan, which has greatly decreased in recent years. A remarkable decrease has been observed in the Nakatsu tidal flat, where current yields are less than 0.02% of the maximum yield. Possible explanations for this decline are: 1. limitation on recruitment due to overfishing; and 2. the demographic processes of growth and mortality have been altered by environmental changes, such as rise in seawater temperature or decrease in phytoplankton abundance. However, because of a lack of demographic information (e.g., the initial densities of larval settlement and mortality and growth rates post-settlement), the reasons for the decline, and the relative importance of each period in the life cycle in determining population abundance, remain unclear. Despite the decline, we observed high levels of recruitment of 0-year-class clams on the Nakatsu tidal flat in spring 2005, where more than 10,000 individuals m -2 3-5mm in shell length, estimated to have settled during the previous autumn, were observed. To obtain demographic information on the Nakatsu clams, we investigated two factors. First, we investigated the distribution of the 0-year-class clams and their rate of change in density as a combination of mortality, emigration and immigration on the whole tidal flat after a year. Second, we investigated the rate of change in the density and growth of clams after settlement in the center of the flat for 3years. The rate of decrease in the density of the 0-year-class clams over the whole tidal flat after a year was greater at the stations where the initial density was higher. This suggests that density-dependent processes such as predation or competition may affect population levels. In the center of the flat, the initial density of settlement was more stable than the rate of decrease after settlement. These results suggest that the clam population on this tidal flat is probably suppressed by variable but high mortality rates after settlement, not by recruitment limitation. © 2012 Elsevier B.V.


Tomaru Y.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Fujii N.,Fukuoka Fisheries and Marine Technology Research Center | Oda S.,Fukuoka Fisheries and Marine Technology Research Center | Toyoda K.,Japan National Research Institute of Fisheries And Environment of Inland Sea | And 2 more authors.
Aquatic Microbial Ecology | Year: 2011

Diatoms are prominent primary producers that play an important role in global carbon cycles. Diatom dynamics are, therefore, important for biogeochemistry, fisheries and earth science. Viral infection is now assumed to be one of the most significant factors affecting diatom dynamics. However, few studies, based on practical field data, have focused on the relationship between diatoms and viruses in natural waters. To elucidate on this relationship, we assessed the temporal change in the abundance of diatoms and their viruses on the western coast of Japan from 2004 to 2009. Three species of diatoms were used as hosts to enumerate viruses in water and sediment samples: Chaetoceros debilis, C. tenuissimus and C. salsugineum. Diatom viruses in the water column rapidly increased during C. debilis and C. tenuissimus blooms, maintaining a high abundance throughout the blooming period. These data suggest the potential importance of viruses in controlling the population dynamics of diatoms in natural environments. The number of viruses in sediments fluctuated considerably, even during non-blooming periods, which suggests that virus-infected diatom cells were supplied to the sediments from water-column populations throughout the year. This process might be an important strategy to reduce the impact of viruses on diatom populations. Because diatom populations are thought to have an intimate relationship with their viruses in natural waters, further studies of diatom dynamics should include the effects of viral infections. © Inter-Research 2011.


Watari S.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Ishitani M.,Fukuoka Fisheries and Marine Technology Research Center | Oda S.,Fukuoka Fisheries and Marine Technology Research Center
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2011

A stock assessment of Japanese mantis shrimp Oratosquilla oratoria was conducted using research data sampled by small trawl vessel in the Buzen Sea, Seto Inland Sea, Japan, from 2007 to 2009. The fishing mortality coefficient estimated for every half-year from the 2007 year class suggested that the reduction of population by discard began soon after recruitment. The survival rate after one year of recruitment was estimated as 13.4%. The reduction of individuals before growing to the minimum landing size was large. The yield per recruit and spawning per recruit analyses show that to increase both catch and egg production, reduction of fishing effort until two years after settlement is effective. It is particularly important to reduce the fishing effort during the next summer after settling which includes high discard mortality.


Senjyu T.,Kyushu University | Matsui S.,Fukuoka Fisheries and Marine Technology Research Center | Han I.-S.,South Korean National Fisheries Research and Development Institute
Journal of Oceanography | Year: 2010

Spatiotemporal characteristics of interannual temperature variations in the Tsushima Strait are investigated on the basis of historical hydrographic data applying the same procedures as Senjyu et al. (2006). Empirical orthogonal function (EOF) analysis revealed that the most energetic mode of variation (the EOF first mode), which accounts for about 31. 5% of the total variance, is the in-phase temperature change for the entire strait. The wintertime temperature variation described by the first mode is associated with the wintertime heat flux in the northern East China Sea, while they are poorly correlated in other seasons. The large standard deviation in the time coefficient of the first mode in August suggests a relationship with the horizontal heat advection in summer in the northern East China Sea. On the other hand, the EOF second mode, which explains about 12. 6% of the total variance, is associated with the stratification and baroclinicity in the strait. The time coefficient of the EOF second mode negatively correlates with the baroclinic volume transport through the strait in summer. Comparison of temporal variations among the leading EOF modes for temperature and salinity shows no significant correlations. This indicates that the principal modes of variation in temperature and salinity vary independently within an interannual timescale. © 2010 Springer Science+Business Media B.V.


Tomaru Y.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Toyoda K.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Toyoda K.,Keio University | Kimura K.,Japan National Research Institute of Fisheries And Environment of Inland Sea | And 3 more authors.
ISME Journal | Year: 2012

Diatoms are considered the most successful and widespread group of photosynthetic eukaryotes. Their contribution to primary production is remarkably significant to the earth's ecosystems. Diatoms are composed of two orders: Centrales and Pennales. Thus far, viruses infecting centric diatom species have been isolated and characterized; however, viruses infecting pennates have not been reported. Here, we describe the first isolations and preliminary characterizations of two distinct pennate diatom viruses, AglaRNAV (31 nm in diameter, accumulates in the host cytoplasm) and TnitDNAV (35 nm in diameter, accumulates in the host nuclei) infecting Asterionellopsis glacialis and Thalassionema nitzschioides, respectively. Their genomes contain a single-stranded RNA of approximately 9.5 kb, and a closed, circular single-stranded DNA of approximately 5.5 kb harboring a partially double-stranded region, respectively. Further analysis of these viruses may elucidate many aspects of diatom host-virus relationships. © 2012 International Society for Microbial Ecology All rights reserved.

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