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The student handbook (Gakubu-Annai or Gakusei-Binran) is distributed to all the freshman students in Hokkaido University at the first guidance class. This book provides various instructions on daily student life as well as general information for academic programs given by different undergraduate schools or faculties. In the chapter related to the Department of Fishing Science (DFS), Faculty of Fisheries, precondition sentence, female students are not suitable for DFS or similar sentences, was continuously found in the student handbook from 1980 to 1992. Such a statement presumably gave negative influence on female students, when choosing the undergraduate program to study. Although two female students graduated the department of Food Science and Technology, Faculty of Fisheries, for the first time in 1953, female students who graduated DFS first appeared in 1978. They decided to study fishing science despite the influence of the statement. Here, we examined the relationship between descriptions in the student handbook and percentages of female students in undergraduate and graduate programs of the Faculty of Fisheries Sciences, Hokkaido University.

Time series of the number of infected individuals is measured to understand the dynamics of an infectious disease and to evaluate the effectiveness of countermeasures against it. However, in fish diseases, it is often difficult to record the time series of the infected fish owing to i) ambiguous clinical symptoms during the onset of disease and ii) cost of diagnosis. To address this issue, we established a mathematical modeling-based method to infer time series of the number of infected fish by coupling the experimental infection and field data on the outbreak of the disease. This method enables to reconstruct time series of the number of infected fish using mortality data obtained from the experimental infection. The reconstructed time series enables to estimate the transmissibility of fish diseases. We studied Oncorhynchus masou virus (salmonid herpesvirus 2) disease (OMVD) using Rainbow trout (Oncorhynchus mykiss) as a model for analysis and estimated the lethality rate of OMVD infection and the basic reproduction number (R0), i.e., transmissibility of OMVD. Our results revealed that larger fish (>= 200 g) showed a higher OMVD lethality rate and R0s when compared with smaller fish (

Pathogenicity of a rainbow trout isolate RtNa-0010 of Oncorhynchus masou virus (OMV = salmonid herpesvirus 2) was investigated in salmonids and cyprinids. Immersion method was used to challenge three species of salmonid fish with RtNa-0010 and OMV reference strain 00-7812 at a dose of 100 TCID50/mL for 60 min. Cumulative mortality of rainbow trout was 3 and 51 of 51 fish when challenged with 00-7812 and RtNa-0010 respectively. When six salmonids and three cyprinids were challenged with RtNa-0010 (10(3)TCID(50)/fish) by intraperitoneal injection, mortality rates were 85%, 10% and 0% for rainbow trout, whitefish Coregonus lavaretus maraena and other tested fish respectively.

魚介類の腸内細菌叢に関する研究が進み，近年は分子生物学的手法を用いた解析法が導入され，多くの知見が集積され，その全容解明と働きが徐々に解明されてきている．成長促進や疾病予防に関与するプロバイオティック微生物の発見のみならず，食の安全にまでリンクした研究が展開できるようになってきた．ここでは水産分野でのプロバイオティクス研究の一つとして，種苗生産過程における仔稚魚のウイルス病予防の観点から，抗ウイルス活性を有する腸内細菌を用いた疾病予防についての研究成果を概説する．淡水生活期のサケ科魚類の腸内菌叢の主体を成すAeromonas属細菌を対象に伝染性造血器壊死症（IHN）ウイルスに対する抗ウイルス作用を示す菌株のスクリーニングを行い，90％以上のプラーク減少を示す菌株を3株得た．分離菌は飼料ペレット成分を栄養源として抗ウイルス物質を産生し，ペレットに10％の割合で菌体培養液を混ぜ経口投与すると，腸内容物も強い抗IHNV活性を示した．分離菌添加ペレットを3週間ニジマスおよびサクラマスに投与後，100TCID50/mlのIHNVで浸漬攻撃を行ったところ有意な差が認められた．マツカワやヒラメの腸内細菌であるVibrio属細菌を対象に，抗IHNV，サケ科魚ヘルペスウイルス（OMV）およびウイルス性神経壊死症（VNN）原因ノダウイルス（BF-NNV）活性を調べ，3者に対し強い抗ウイルス効果を示すVibrio sp. 2IF6株を得た．生物餌料のアルテミア卵を次亜塩素酸ナトリウムで消毒後，滅菌海水で孵化させ分離株を添加して培養すると，アルテミアホモジナイズ液は培養2日後にBF-NNVに対して90％の感染価減少を示し，培養液は99％を示した．このアルテミアを給餌したマツカワの腸内容物の10倍希釈は105.8TCID50/mlのBF-NNVの感染価を99.99％以上減少させた．換水率0～300％で60日間飼育したマツカワ仔魚にVNNは発生せず，生存率は通常飼育区より高くなった．シオミズツボワムシの複相単性生殖卵を消毒し，ヒラメの腸内から分離した抗OMV活性を示すV. alginolyticus V-23株添加したワムシをヒラメ仔魚に給餌し，103TCID50のOMVを不活化する最大希釈倍数で抗OMV活性を求めると，給餌20日以降，分離菌添加区のヒラメの腸内容物では対照区の2～5倍，飼育水では対照区の2～4倍の抗OMV活性が測定された．さらに，貝類ではカキの中腸腺から分離したV. neptunis V-176株がNorovirus代替えネコカリシウイルスを，Vibrio sp. V-4株がカキヘルペスウイルス（OsHV-1μVar）代替えOMVを不活化した．これらの細菌をカキの餌料である無菌化キートセロスに添加して給餌すれば，魚類と同様にウイルス病の予防あるいは不活化が期待できると考える．

The success of the methods employed in the detection of Aeromonas salmonicida depends on several factors including detection limits which are not always considered when planning a diagnostic protocol. First, detection limits of A. salmonicida by Coomassie Brilliant Blue Agar (CBBA) culture, Immuno-Fluorescence Antibody Test (IFAT), Coagglutination test (CoAgT) and Polymerase Chain Reaction (PCR) were analyzed, then a controlled wet-lab experiment was conducted using 60 masu salmon (Oncorhynchus masou) fry inoculated with A. salmonicida and based on the results obtained, an epizootiological survey of selected rivers in Hokkaido was then conducted. Detection limits were 10^2 for CBBA, 10^4 for the IFAT, 10^5 for PCR and 10^3 for the CoAgT from an original de A. salmonicida broth culture of 1.3 x 10^8 CFU/mL demonstrating that CBBA and the CoAgT were better at detecting the bacteria at low concentrations. The wet-lab analysis produced results of detection limits of a similar trend, with CBBA, IFAT, PCR and CoAgT at 10^-3, 10^-3, 10^-1 and 10^-3 from kidney samples of 9.9 X 10^4 CFU/g respectively. The results from the epizootiological survey in Hokkaido showed positive from CBBA with IFAT, CoAgT and PCR corroborating them in varying degrees thus demonstrating the importance of a multi-diagnostic approach in scenarios of this nature.

To control the hygienic conditions of fishery products from catching to landing and processing, both qualitative and quantitative bacterial observations at fishing ports must be considered. Thirty-six fishing ports in Hokkaido, northern Japan, were selected and the distributions of coliform bacteria were studied at these sites. Coliforms were observed from all fishing ports, and Escherichia coli were observed from 30 fishing ports. Especially, in relation to the number of coliform bacteria and E. coli, fishing ports which are located near a river show higher levels than any other fishing ports., 漁港における港内海水の大腸菌および大腸菌群の分布に，漁港の形状が与える影響について検討した。北海道内の 36 漁港において全ての漁港内海水から大腸菌群が，30 漁港から大腸菌が分離され，河川が付近にある漁港では特に高い値を示す傾向がみられた。漁港内で分離される大腸菌および大腸菌群は河川水の流入と関係があることが示された。漁港の入り口と河川の位置との関係を中心に 3 漁港を調べたところ，漁港の入り口が河川のある方向を向いている場合に，分離菌数が多くなる傾向が明らかとなった。

冷水病菌，せっそう病菌，IHNVおよびOMVで汚染したニジマス卵を供試して，等調液洗卵の除菌効果を定量的に明らかにするとともに，ニジマス卵を使用した感染試験を行い，卵内感染の防止効果について検証した。その結果，冷水病菌，せっそう病菌ではそれぞれ10(3)CFU/ml，10(5)CFU/ml，IHNVおよびOMVについては10(4)TCID50/ml程度の菌体あるいはウイルスが等調液洗卵により除去されることが明らかとなった。また，シャワー洗卵においては，等調液量を増加させることにより，冷水病菌およびせっそう病菌の除菌量が増加した。さらに，冷水病菌で高度に汚染した卵を濯ぎ洗卵した場合には，卵内感染の割合が低くなり，シャワー洗卵をした卵では卵内感染卵は検出されなかった。これらの結果から，等調液洗卵法は卵表面に存在する細菌，ウイルスの除菌あるいは除去効果があり，卵内感染のリスクを小さくするために有効な方法であることが示された。, Egg-washing with isotonic solution has been used to improve the artificial fertilization in fresh-water salmon aquaculture. Usually, unfertilized eggs are rinsed twice or three times with isotonic solution and showered before fertilization. We investigated the effect of egg-washing using rainbow trout eggs on elimination of some causative agents of cold water disease (Flavobacterium psychrophilum), flunculosis (Aeromonas salmonicida), infectious hematopoietic necrosis (IHNV) and Oncorhynchus masou virus disease (OMV), quantitatively and on prevention of intra-ovum infection with F. psychrophilum. The number of live bacterial cells or virus infectivity titers which were eliminated by egg-washing, was 10(3)CFU/ml in F. psychrophilum, 10(5)CFU/ml in A. salmonicida, or 10(4)TCID50/ml in both of IHNV and OMV. In shower washing, the eliminated extent of F. psychrophilum or A. salmonicida cells increased with increasing isotonic solution volume. The ratio of intra-ovum infection with F. psychrophilum was clearly less in rinsed eggs than in non-treated eggs, and result of detection from showered eggs was negative. These results suggest that egg-washing with isotonic solution is very effective to eliminate the bacteria or viruses on egg surface and is able to decrease the risk of intra-ovum infection.

漁獲から加工場に至る水産物の衛生管理・品質向上を図るうえで，漁港で利用されている海水の実態の把握が重要であり，港内海水の水質，一般生菌数および食中毒菌の生菌数を調査した。調査した羅臼・標津・由比・博多の各漁港の港内海水の水質項目のうち，SS と COD 値は総じて水産用水基準値を上回る結果となった。漁港内海水から大腸菌群・大腸菌が検出され，由比・博多では Vibrio parahaemolyticus が分離された。市場の殺菌海水あるいは海洋深層水からは大腸菌は分離されず，洗浄による除菌効果も認められた。, To control the hygienic conditions of fishery products from catching to landing and processing, both qualitative and quantitative bacterial observations at fishing ports must be considered. Four fishing ports, Shibetsu and Rausu in Hokkaido, Yui in Shizuoka prefecture, and Hakata in Fukuoka prefecture, were selected and the distribution of coliform bacteria and human pathogenic vibrio species were studied at these sites. Coliforms and Escherichia coli were observed from all four fishing ports, while Vibrio parahaemolyticus was observed from Yui and Hakata fishing ports. The number of V. parahaemolyticus in the surface seawater varied seasonally from

A study was carried out in order to reduce the hygienic bacteria from sea urchin Strongylocentrotus nudus viscera. The effect of pre-culturing before shipment using electrolyzed seawater on reduction of Vibrio parahaemolyticus and viable bacteria inhabiting the sea urchin viscera was examined. When 3% salt water suspended with V. parahaemolyticus was electrolyzed, the viable number of V. parahaemolyticus was reduced by more than 99.99% after treatment with 0.23mg/L chlorine for one minute. In the case of sea urchin reared with electrolyzed seawater containing 0.76mg/L chlorine for 2 days, a lot of dejecture was discharged, and the bacteria in the sea urchin viscera were reduced by more than 90%.

Norovirus (NV) はヒトの腸管上皮で増殖するウイルスであり、近年糞口感染が問題となっている。しかし、二枚貝、特にカキがウイルスを濃縮し食中毒を引き起こすことから、水産分野でもその対策が急がれている。カキのNV浄化法の確立を目的として、培養できないNVの代替に、同じ科に属する feline calicivirus (FCV) を用い、環境水中およびカキ消化管中での生存性、紫外線、電解処理および高静圧処理による不活化効果について検討した。FCVの感染価は保持温度が高いほど速やかに減少したが、10℃以下では検出限界以下となるのに2～3週間を要した。さらにカキ消化管中でも感染価は速やかに減少し、抗FCV活性を有する細菌も分離され、消化管内細菌の影響が示唆された。しかし、FCVを99.9％以上不活化するには2.5×10^4μW•sec/cm2の紫外線照射を要した。電解処理では、3％NaCl溶液および海水でそれぞれ有効塩素濃度0.23および0.41mg/L・1分間の処理により感染価が99％以上減少し、ほぼ検出限界以下となった。高静圧処理では、カキの殻を外す条件である80MPa・40℃・5分間の処理で、FCVの感染価が1～2桁減少した。以上の結果から、カキのNV浄化には電解海水を用い、水温を20℃程度とし、高静水圧処理を組み合わせることが効果的であると考えられる。ただし、代替ウイルスによる試験であることから、今後はNVの感染性評価系の確立が急務と考える。, Oysters (Crassostrea gigas) harvested from major culture areas are sometimes contaminated with norovirus (NV). Elimination of NV from oysters is needed to reduce losses for oyster traders and farmers because it causes gastroenteritis in humans by a fecal-oral route. However, there is little information on survival of NV in marine environments and under inactivating conditions because determination of infectivity of NV by cell culture methods is impossible. Nevertheless, cell propagation of feline calicivirus (FCV), a surrogate for NV, is possible. Thus, in the present study, survival of FCV in aquatic environments and virucidal effects of UV irradiation, hypochlorite produced by electrolysis of seawater and high hydrostatic pressure were examined. FCV infectivity decreased quickly with temperature increase in seawater. Above 20℃, for a period of 1 week, infectivity decreased to below detection limits. FCV was more unstable in non-treated seawater than in sterilized seawater. Furthermore FCV is unstable in intestinal contents of oyster. Therefore, FCV was inactivated by antiviral substances produced by intestinal bacteria. FCV was inactivated (≧99.9%) by UV irradiation at closes of 2.5×10^4μW•sec/cm2. At the concentration of 0.23 and 0.41 mg/L of chlorine, produced by electrolysis of 3% NaCl solution and seawater reduced infectivity more than 99% in 1 min, respectively. Seawater electrolyzers have ability to treat large volumes of water and cost performance of this method is better than that of UV irradiation. Challenged with high hydrostatic pressure, FCV was almost completely inactivated at 200 MPa for 5 min. Oysters separated from their shells under a pressure of 80 MPa for 5 min at 40℃. Under these conditions, one to two-log. inactivation of FCV was observed. From these results, it is considered that electrolysis of seawater at 20℃ or above is a useful method for post harvest elimination of NV from oysters. High hydrostatic pressure is also effective for inactivation of NV.

Effect of manipulation of dietary rotifer Brachionus plicatilis bacterial flora on the intestinal bacterial flora of Japanese flounder Paralichthys olivaceus larvae was investigated. Manipulation was done by disinfecting rotifer eggs to reduce viable bacterial counts and then by inoculating hatched rotifers with non-sucrose fermenting Vibrio splendidus strain V-15 to make the bacterium dominant in the rotifers. Flounder larvae were fed the manipulated rotifers and intestinal bacterial flora of the fish was monitored. The dominant intestinal bacterial flora of the flounder became Vibrio spp. These results indicate that intestinal bacterial flora of flounder can be artificially controlled by manipulating bacterial flora in diets., 消毒前のワムシ卵および未処理区の孵化ワムシの細菌叢は，共にFlavobacterium属が主体を成していたことから，孵化前後でワムシの菌叢は変化しないことが示された。また，消毒して孵化させた後にV. splendidus V-15株を添加した区のワムシの細菌叢はVibrio属が主体を成していた。これらの結果から，ワムシの細菌叢は制御可能であることが示唆された。次いで，ショ糖分解能のない抗ウイルス活性を有するV. splendidus V-15株優勢ワムシをヒラメに給餌した。ヒラメ腸管内におけるVibrio属細菌のうち，ショ梼非分解薗の割合は未処理区で62%，消毒区で59%，菌添加区で100%となり，ヒラメの腸内細菌叢も制御可能であることが示唆された。

Special Issue: International Symposium on Koi Herpesvirus Disease : Strategy for Koi Herpesvirus Disease Control. 13 March 2004. Yokohama, Japan., Survival of three salmonid viruses and two marine fish viruses in fish rearing water or coastal sea water were observed at 0, 5, 10 and 15 ℃ for 7 or 14 days. Interaction between viruses and microorganisms present in the rearing water was observed. Infectious pancreatic necrosis virus (IPNV) and fish nodavirus (BF-NNV) were stable in waters used at every temperature tested for 14 days, but it was observed that, for infectious hematopoietic necrosis virus (IHNV), Oncorhynchus masou virus (OMV), and hirame rhabdovirus (HIRRV), as the temperature increased, the loss of infectivity also increased. When IHNV and OMV were suspended in filtrated and autoclaved rearing water, infectivity was reduced in comparison with the untreated water. Subsequently, adsorption of IHNV to mud or small particles was studied. IHNV adsorbed to several clays (kaolin, bentonite, Japanese acid clay) and diatomaceous earth in sterilized water with a wide range of pH (5-11) at concentrations of 1, 10, and 100 mg/mL. Except for bentonite, infectivity of clay-adsorbed IHNV persisted for at least 9 weeks. The clay-adsorbed IHNV also persisted in infectivity to rainbow trout Oncorhynchus mykiss, causing cumulative mortality rates of more than 73 %. Then, inactivation effects of UV irradiation, ozonization, and electrolyzation of water were studied against six fish rhabdoviruses, three fish herpesviruses, one fish birnaviruses, one fish iridovirus, and one fish nodavirus. Six rhabdoviruses, three herpesviruses, and lymphocystis disease virus were found to be sensitive to UV irradiation, ozonization, and electrolyzation. Susceptibility of IPNV, chum salmon virus (CSV), and BFNNV to UV was found to be low. IPNV and CSV were low sensitive to ozonization and electrolyzation. Virucidal effects of six kinds of disinfectants were examined against OMV, IPNV, IHNV, and HIRRV at 15 and 20℃ for 30 sec and 20 min. At 15℃ for 20 min, minimum concentrations showing 100 % plaque reduction of viruses tested by iodophore, sodium hypochlorite solution, benzalconium chloride solution, saponated cresole solution, formaldehyde solution, and potassium permanganate solution were 40, 50, 100, 100, 3500, and 16 ppm, respectively.

To control hygienic conditions at fishing ports, qualitative and quantitative bacterial observations have to be considered. In the fishing port located at Shibetsu town, Hokkaido, where the hazard analysis and critical control point (HACCP) system is performed, the distribution and composition of heterotrophic bacterial flora and coliform bacteria were studied in this hygienically controlled site. There was a little difference in the quallty of water collected from inside and outside of the harbor. The number of viable bacteria in the surface seawater varied seasonally from 10^2 to 10^4 CFU/mL. The generic composition of bacteria collected from back part of the harbor, entrance of the harbor, and the front of the fish market was compared. The generic composition of the bacterial flora included the genera Pseudomonas, Alteromonas and Vibrio, which were observed through the year. Moraxella and gram-positive bacteria were also isolated in front of the fish market. Coliform were isolated inside and outside of the harbor throughout the year, and their counts increased as water temperature increased.

Seawater in a fishing port was electrolyzed to induce hypochlorite up to approximately 1 mg/L for the reduction of viable bacterial count because disinfection of seawater is important for the prevention and control of hazards in seafoods. The number of viable bacteria in a fish holding tank was lowered from 10^4-10^5 mg/L to 10^0-10^1 mg/L after electrolization of seawater and the low level of viable bacterial count was kept for at least 3 hours. The reduction rate of chlorine concentration of the electrolyzed seawater in the fish holding tank was reduced by the addition of ice and by covering with a thermal insulating sheet. However, the chlorine concentration decreased when fish were put into the fish holding tank. In a fisher-boat tank, viable bacterial count remained less than 100 CFU/mL for at least 60 minutes when ice was present. It was also shown that electrolyzed seawater was useful for disinfection of deck or fishing equipment.

10th International Symposium for Veterinary Epidemiology and Economics. 17-21 November 2003. Vina Del Mar, Chile., This study was carried out for the purpose of establishing control methods for furunculosis affecting propagated salmon in Japan. We determined the distribution and prevalence of A. salmonicida among asymptomatic adult chum (Oncorhynchus keta), pink (O. gorbuscha) and masu salmon (O. masou) returning to rivers on the island of Hokkaido and on the mainland of Honshu. During 1979-2002, a total of 22,109 chum, pink and masu salmon were collected from the rivers in Hokkaido and Honshu. We isolated A. salmonicida from the chum salmon in 21 of the 34 rivers examined and the overall prevalence was 12.2 % in the infected stocks. The prevalence of the agent in pink salmon and masu salmon was 4.6 % and 1.4 % respectively. Using CBB medium, we also examined the chum salmon from the Chitose River catching site. The prevalence of the agent on gill surface was high (50%) at the catching site and decreased among fish in the holding pond in the river. The bacteria appear to be spread during fish migration in the river and during transportation of the fish from the capture site to the holding pond. Recently, the agent was isolated from the gill surface of chum salmon caught off the coast of the eastern part of Hokkaido, but the prevalence was low (1.7%). To control furunculosis in salmonids, the fish should be held for maturation in ponds under conditions of low density and the fish should be disinfected to prevent spread of furunculosis before placement in the holding pond.

短報, 水産廃棄物であるヒトデの有効利用を目的に，魚類飼育排水処理施設由来細菌のヒトデ成型骨片への付着性を検討した。5 回洗浄を行った後でも，ヒトデ成型骨片の生菌数は 10^8 CFU/g 程度であった。また，ヒトデ成型骨片と市販ろ材への細菌の付着量を比較したところ，どのろ材も洗浄後の生菌数は 10^7 CFU/g 程度であった。以上の結果から，ヒトデ成型骨片は市販ろ材と同様に細菌付着用のろ材として使用できることが明らかとなった。

The bactericidal and virucidal effects of hypochlorite produced by batch electrolytic system were examined for fish pathogens. Sodium chloride solutions, ranging from 0.5 to 3%, were electrolyzed and the concentration of chlorine produced was measured. Almost same concentration of chlorine was produced when 1.0% or more NaCl solution and seawater were electrolyzed. Fish pathogenic bacteria or virus was added to electrolyzed water and exposed to hypochlorite. More than 99% cells of Vibrio anguillarum, causative agent of fish vibriosis, were killed when the bacteria were exposed to 0.21 mg/l hypochlorite for 1 min. Yellowtail ascites virus (YAV) and hirame rhabdovirus (HIRRV), the causative agents of viral ascites disease and rhabdovirus disease of marine fish, were inactivated more than 99% after treatment with 0.42 mg/l hypochlorite for 1 min. The number of viable bacteria in the hatchery supply-seawater was reduced more than 99% when the water was treated with hypochlorite of 0.54 mg/l for 1 min. And more than 99% cells of viable bacteria in the waste-seawater were killed when the water was treated with hypochlorite of 0.64 mg/l for 5 min. The batch system developed in this study revealed remarkable bactericidal and virucidal effects, which were very similar to those in continuous flow-water system., バッチ式海水電解装置を用い，3%食塩水を電気分解して得られた電解水の魚類痛原細菌あるいはウイルスの殺菌・不活化効果を検討した。同時に飼育用水ならびに飼育排水の殺菌効果も検討した。1%濃度以上の食塩水を電気分解すると海水程度の次亜塩素酸が生成した。有効塩素濃度0.21mg/l，1分間の処理で供試細菌が99%以上，0.42mg/l，1分間の処理で供試ウイルスが99%以上不活化された。飼育用濾過海水については0.54mg/l，1分間の処理で99%以上，飼育排水についても0.64mg/l，5分間の処理で99%以上の殺菌効果が得られた。また，流水式海水電解装置との比較試験により，両装置はほぼ同等の殺菌能力を有すことが明らかになった。

The bactericidal effect of hypochlorite produced by a continuous flow electrolyzer on hatchery waste-seawater was investigated. The number of viable bacteria in the waste-seawater was reduced more than 99% when the water was treated with hypochlorite at 0.6mg/L for 1min, and over 99.9% of bacteria was reduced when treated with 1.0mg/L for 1min. In the next experiment, one part, 2.0m3/h of hatchery waste-seawater was treated with electrolyzer and produced hypochlorite was mixed with the remaining, 16.5m3/h waste-seawater. More than 99% of viable bacterial was reduced after treatment with 0.5mg/L of total residual chlorine for 1min. The bactericidal efficacy of electrolysis was almost the same as that of ultraviolet irradiation (1.0×10^5μW・sec/cm2) or ozonization (TROs 0.5mg/L, 1min) of seawater. Electrolyzation is able to treat a large volume of waste seawater compared with the ultraviolet irradiation or ozonization.

The bactericidal and virucidal effects of hypochlorite produced by electrolysis of salt water were examined for pathogenic bacteria and viruses of fish. A three percent solution of sodium chloride that contained pathogenic bacteria or virus was electrolyzed and the organisms were exposed to hypochlorite. More than 99.99% of the cells of Vibrio anguillarum and Aeromonas salmonicida, the causative agents of fish vibriosis and furunculosis respectively, were killed when the bacteria were exposed to 0.1mg/l hypochlorite for one minute. Yellowtail ascites virus (YAV) and hirame rhabdovirus (HIRRV), the causative agents of viral ascites disease and rhabdovirus disease of marine fish, were inactivated >99.99% after treatment with 0.58mg/l hypochorite for one minute. The bactericidal and virucidal effects of hypochlorite produced by electrolysis (3.5m3/h, 0.1A) are greater than those of the chemical reagent. The purity of the sodium chloride used influences the production of hypochlorite. Sodium chloride obtained as a super grade chemical reagent is more effective than sodium chloride that is used for food. However, a sufficient disinfectant effect was observed in electrolyzed seawater, which could be applied in aquaculture.

This paper presents the methods of the development of fishing ports for the supplying of safe seafood products, based on the some rules on food hygiene control and on the eco-label system which is useful for fishery resource management in Japan. First, we analyzed the issue of the hygiene control for fresh fish on the distribution process from the landing places to the consumers and proposed the method to estimate the hygiene level with the two factors; the water quality, control and the sanitary condition of the working areas at the fishing ports, landing places and the auction halls on the distribution process. Secondly, we proposed the method to select whether fishery products contribute to being sustainable or not, so as to secure the validity of the sea food hygiene control at the fishing ports.

Treatment of supplied water with a high quality ultraviolet (UV) lamp was examined for prevention of scuticociliatosis of farmed juvenile Japanese flounder (Paralichthys olivaceus). In an examination for the ciliate-cidal effect of UV irradiation, scuticociliates showed low susceptibility to UV compared with fish pathogenic viruses or bacteria, the minimal killing dosage being 2.0 × 10^5 μW・sec/cm^2. UV treatment of supplied water to the tank was performed in a flounder farm in southern Hokkaido, where scuticociliatosis frequently occurred. It was revealed that the UV treatment at 3.0 × 10^5 μW・sec/cm^2 was effective to prevent scuticociliatosis.