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2020年秋季に宇和島湾で発生したKarenia mikimotoi赤潮と急潮の関係
Get PDF2020年の宇和島湾において，観測史上最も遅い9月上旬から11月中旬にかけて有害渦鞭毛藻Karenia mikimotoiの赤潮が発生した。本種の遺伝子は冬季から検出されていたものの，黒潮の離岸に伴う低水温や競合種の存在によって増殖が遅れ，8月中下旬に発生した急潮が，水温上昇，競合種の拡散，底層への栄養塩供給をもたらすことで増殖を促進した可能性がある。さらに，台風が西風によってプランクトンを宇和島湾奥部に集積させるとともに，日照時間を減少させたため，赤潮の発生に至ったと考えられる。journal articl
Estimation of hemolymph αco2 and pKapp in disk abalone Haliotis (Nordotis) discus discus between 10°C and 20°C
Get PDFWe investigated the effect of temperature on disk abalone Haliotis (Nordotis) discus discus hemolymph CO2 solubility coefficient (αco2) and the apparent dissociation constant of carbonic acid (pKapp). The disk abalone hemolymph was equilibrated with a standard CO2 gas mixture between 10°C and 20°C, to obtain expressions for αco2 and pKapp as a function of temperature. The relationship between αco2 and temperature (T) is expressed as follows: αco2 = 74.005 1.2936 • T 0.00944 • T2 . And the relationship between pKapp and temperature expressed as follows: pKapp = 6.4675 0.08682 • T + 0.003996 • T2 . In these equations, the parameter units are °C for T and µM/L/torr for αco2. The non-bicarbonate buffer values (ꞵNB), obtained as a regression coefficient relating pH and [HCO3 – ], were 2.5 Slykes at 10°C, 2.2 Slykes at 15°C, and 3.4 Slykes at 20°C. These equations enable estimation of hemolymph αco2 and pKapp between temperatures of 10°C and 20°C.編集：水産大学校departmental bulletin pape
Estimation of the uptake of polycyclic aromatic hydrocarbons desorbed from polyethylene microplastics in the digestive tract of the red seabream (Pagrus major) and mummichog (Fundulus heteroclitus)
Get PDFThe vector effects of microplastics (MPs) in natural marine environments and their contribution to polycyclic aromatic hydrocarbon (PAH) bioaccumulation in fish are still unknown. This study, therefore, aimed to evaluate the effects of MPs on carrying PAHs under conditions close to the actual marine environments. The PAH content sorbed onto MPs from seawater positively correlated with the octanol/water partition coefficient (log KOW) in both polyethylene and polystyrene MPs. The desorption rate constant (k2) of PAHs sorbed onto MPs from seawater in the digestive tract was calculated using two marine teleost fish in an in vitro desorption experiment. A negative correlation was observed between the log KOW and k2 of the PAHs. The PAHs with larger log KOW and lower water solubility are easier to sorb onto MPs and less likely to desorb in the digestive tract of marine fish species. The estimation of PAH uptake into the fish body using the k2 of three selected PAHs (phenanthrene, pyrene, and chrysene) indicated that >95 % of the chemicals were uptaken from seawater via gills. It was presumed that there was an additional uptake of PAHs into the fish body (vector effect) due to desorption from MPs in the digestive tract when marine fish ingested MP that was sorbed and concentrated with PAHs. The degree of uptake was, however, much lower than that from seawater via gills. The vector effect of PAHs by MPs in the actual sea may be negligible, and the risk is presently considered to be low.journal articl
Comparative study of experimental infection against koi carp using Carp edema virus.
Get PDFViral edema of carp is caused by Carp edema virus and is a major carp disease listed on the WOAH list of emerging infectious diseases. However, an effective experimental infection method that can control virus copy number has not been established. In this study, we compared three experimental infection methods: immersion infection using gill suspensions from diseased fish (immersion method), infection by rearing water from diseased fish (rearing water method) and co-infection method. Cumulative mortality in the immersion groups ranged from 40 to 60%, while that in the rearing water infected and co-infected groups ranged from 80 to 100%. The rearing water method can be used to control the viral DNA copy number and to perform experimental infections when frozen storage is possible. Thus, we performed the same experimental infection using frozen rearing water and found no disease or mortality, indicating that stable experimental infection using the rearing water method is difficult. The immersion method has a lower mortality rate than the other two methods, and it requires a large amount of gill tissue because of the low number of virus DNA copies that can be obtained from the gill tissue. However, it is possible to control the number of virus DNA copies and to preserve the gill tissue suspension by freezing. Therefore, the imme編集：水産大学校departmental bulletin pape
水素細菌Hydrogenovibrio marinus MH-110の養魚飼料としての生産および利用に向けた培養，成分分析および短期飼育による特性評価
Get PDFProteins from some bacteria are possible candidates for novel aquafeed ingredients. As a preliminary study to utilize the hydrogen-oxidizing bacterium Hydrogenovibrio marinus MH-110 as a fish feed, we cultured the bacterium in a 10L jar-fermenter with a continuous gas-flow system with H2, O2, and CO2 for 10 hours. The cultivation successfully produced 50.7g of H. marinus bacterial cells, which contained 50% protein with a similar amino acid profile to that in a common fish meal-based feed. In a subsequent feeding experiment for 8 days using juveniles of the red sea bream (Pagrus major), the digestibility of the bacterial protein was 83%. These results suggest that H. marinus MH-110 could become a viable
option for a protein source for aquafeed.本研究では独立栄養性の水素細菌Hydrogenovibrio marinus MH-110の量産化と養魚飼料化に向けた第一歩として水素など無機ガス原料を用いた通気培養，菌体成分の分析，およびマダイ（Pagrus major）幼魚への給餌試験と消化吸収率の測定を行った。10L培養槽での 10時間培養で乾燥重量 50.7gの菌体が生産された。菌体のタンパク含量は約 50%でアミノ酸組成は一般的な養魚飼料と類似していた。また菌体を 30%混合した飼料を用いた 8日間の給餌飼育ではマダイ幼魚の摂餌と成長が確認され，菌体タンパク質の消化吸収率は約 83%であった。こうした生産面・利用面の特性から，本菌株は養魚飼料におけるタンパク源の選択肢の一つになり得ることが期待された。ファイル名末尾に”_abs_j”のファイルは和文要旨journal articl
Fine-scale spatial distribution of a fish community in artificial reefs investigated using an underwater drone and environmental DNA analysis
Get PDFAlthough artificial reef (AR) effect evaluation is useful for planning the installation of high-rise ARs and their management, few studies have investigated them quantitatively. The fine-scale 2-dimensional fish distribution in ARs was estimated regarding current fields and vertical structures of 2 high-rise ARs (20 and 30 m high at 62 and 72 m depths, respectively) in Tateyama Bay, central Japan, using underwater drone recordings with vertical line transects and environmental DNA (eDNA) metabarcoding. The species detected by video surveys (21 taxa were identified to species, and 1 to genus) were fewer than by eDNA analysis (103 species and 6 genera), especially for pelagic, small-sized, and cryptic fish. Video surveys revealed that demersal fish increased with decreasing horizontal distance from the AR surface within 20 m, and the richness and total fish density were significantly higher upstream of the ARs. Conversely, the fish eDNA concentration showed different patterns, with significantly higher concentrations downstream of the ARs. The richness peaked at horizontal AR surfaces (e.g. reef top), but density of the dominant species peaked near the bottom by video survey. In comparison, eDNA analysis indicated lower richness and higher eDNA concentration of the dominant species at the reef top. Such discrepancies may be explained by the influence of eDNA transport or its specific behavior or buoyancy. Video surveys revealed the growth stage and sex information of 4 species from their morphology, which is not possible using eDNA analysis. This study shows that the advantages of each evaluation method can complement each other.journal articl