The brackish Lake Obuchi in Rokkasho-Village, Aomori, Japan, is bordered by nuclear fuel facilities including a nuclear spent-fuel reprocessing plant under construction. Small amount of radionuclides will be released from the reprocessing plant, when it will be in operation. These radionuclides may enter this lake from the ocean by tides, from the land by rivers, and from the atmosphere by fallout. Therefore, it is necessary to evaluate the impact of released radioac tive substances to assess the safety of the surrounding environment and develop a radionuclide transport model in this lake. As the part for constructing for a radionuclide transport model, a 3-D hydrodynamic model was developed for lake current, salinity and water temperature in Lake and calculated from May to October 1998. The numerical results were compared favorably with the field measurements of water current and salinity indicating the validity and predictive capability of the model in this lake. Field ob servations showed that the model could simulate a formation and elimination of the halocline. Moreover, the model could well describe flow to a back swamp in the ebb-current of the lake's lower layer in the spring. However, as a point of the nonconformity, the salinity of middle layer in the model result was estimated a little lower than field measurement, and it was not possible to express internal wave of a short time period (1.5 to 6 hours) in the model results.

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The Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) has a low light imaging capability designed for clouds detection using moonlight. The OLS has two spectral bands (V and TIR) and V band gains are controlled under the con dition of solar elevation and lunar phase and elevation. This unique capability can also detect nighttime lights such as city lights, and fishing boats. The other hand, V band gain control makes difficulties for quantitative analysis. We developed a method to estimate fishing lights power quantitatively with a single frame of V band image by using reported fishing lights power value from voluntary fishing vessels. This method allows you to analyze DN for a single frame of V band quantitatively without the gains setting information and can also be used as one of utilized fishery resource monitoring system. We hope the method will be of help for keeping rule of International fishery convention reso lution.

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This paper describes long-term operating tests of the unit of the source and conceptual design of very low frequency sources below 30 Hz for monitoring global ocean variability of 10 Mm scale in long-term observation over a decade. An accelerated operating test of the driving units was conducted in a short period equivalent to ten years of 70 Hz source. Variation of strain, impedance and displacement-current sensitivity of five driving units were measured every 10,000 cycle drives. As a result, it was found that there was no significant variation for these parame ters during the experiments. Then, the conceptual design of two types of very low frequency sources is shown. One is an ordinary barrel type using several giant magnetostrictive rods with larger diameter and larger pre-stress than the present 200 Hz source. Another is a bender bar type source constructed with giant magnetostrictive plates. The latter is expected to have a smaller size than the former because the displacement of bending plates can be larger than rods. Some theoretical results are shown.

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A time series dataset is important to understand trends such as SST and NDVI fluctuation in global changes and satellite observation data can be used for those purposes. However, how to generate a time series of cloud free dataset with satellite observation data is a big problem. A time composite method, typically 10-day Maximum Value Composite method (lOdayMVC) is used commonly for the solution but it does not guarantee to complete it. A NRF (Noise Reduction Filter) was developed by authors to implement the lOdayMVC dataset and is adapted for a SST-lOdayMVC dataset that was generated from a time series of Defense Meteorological Satellite Program (DMSP) / Operational Line Scan System (OLS)- Thermal Channel (TIR) data. A cloud free SST dataset was generated by NRF and was evalu ated by using the lOdayMean SST of the Japan Meteorological Agency. Significant reduction of cloud influences was confirmed of the dataset. In this study, thermal data from the TIR were converted to SST by an algorithm using regres sion analysis method, and the multi-channel SST (MCSST) derived from the Advanced Very High Resolution Radiometer (AVHRR) carried on the National Oceanic and Atmospheric Administration polar orbiter series of satellite (NOAA-14) was used as standard data for this re gression analysis.

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A three-dimensional oil fate/transport model combined with an oil toxicity model to simulate the biological effects due to an oil spill is described. Specifically, the focus of this paper is on the effect on fish. However, the model formulation can be extended to determine the effects on other species. The model can simulate oil releases from the water surface or from an underwa ter source. The output from the oil transport and fate model along with the oil toxicity data are used by the oil toxicity sub-model to determine the biological effect. The mortality of a fish kind is estimated by using the Additive Toxicity method. From an economical point of view, Tokyo Bay is the most important bay in Japan. There are six ports in Tokyo Bay: Tokyo, Yokohama, Kawasaki, Yokosuka, Chiba, and Kisarazu. It is also a good fishing ground for pelagic fish and benthic shellfish. In this paper, seven scenarios are simulated which use real biological data in Tokyo Bay. These simulations investigate the differ ence in mortality of different species, as well as the mortalities for nighttime vs. daytime spills and a surface spill vs. an underwater spill. The simulations are the worst-case scenarios during a fishing season.

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Deepest Remotely Operated Vehicle ”Kaiko”, owned by Japan Marine Science and Technology Center (hereafter； JAMSTEC), had lost own vehicle during the research operation by the acci dent of snapping the secondary. JAMSTEC and other Japanese governmental organizations searched the missed vehicle as well as we could. However, it has been missing ever since. The search activities, which many Japanese organizations cooperated and carried out, arc summarized in this subject.

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The full ocean depth ROV Kaiko (Fig.l) of Japan Marine Science and Technology Center, JAMSTEC, started construction in 1993 in order to carry out surveys at any depth in the world oceans. On May 29, 2003, after completing its 296th dive at a depth of 4675 m, the Kaiko op erators could not mate the vehicle and the vehicle end of the secondary cable was fractured. The search for the vehicle was carried out until June 21st from the surface and from the air without success. Kaiko, a full ocean depth ROV system which JAMSTEC spent and developed for six years, is the only investigation system capable of reaching the Challenger Deep, the deepest trench in the world. Kaiko symbolizes the latest technology of JAMSTEC. This accident is the worst since JAMSTEC was founded. JAMSTEC has recognized this ac cident as a serious problem, and established an accident investigating committee to investigate the cause of the accident and to suggest preventive actions. Professor Ura Tamaki of the University of Tokyo, Institute of Industrial Science chairs this committee. The committee pre sented the first report to JAMSTEC on July 30. The contents of the first report described the cause of the accident and a proposal for JAMSTEC to implement needed accident management. This paper summarizes the report of the accident investigating committee. In factory testing, we knew two problems. The first one is that there were some structural problems in the cable termination. Secondary, the strength members would deteriorate by bend ing under high pressure exceeding 1000 kg per square cm.

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In order to investigate the possibility of seasonal succession between a grazing food web and a microbe food web, and the seasonal variation of the dominant species of phytoplankton, an ecosystem model is developed. The prcy-prcdator interactions and the interspecies competition are incorporated into this new model. This improved model is applied to analysis of the Lakes Shinji and Nakaumi ecosystem for 1998. In the model results of physical processes, the tendency of water mass change and the density gradient between the upper layer and bottom layer are reproduced well. The simulated results of the biological processes using the ecological model show good agreement with field data. Especially the release of P04-P from the bottom sediment and the formation of oxygen-depleted water in bottom layer of Nakaumi in summer are reproduced well. Sensitivity analysis suggests that the filtration rate of shellfish and the horizontal diffusivity play important role on phytoplankton blooming in winter. The model also suggests the possibility of the succession of the dominant plankton species.

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Current meter data from various depths near the sea bottom collected for about 1 year at time intervals of 1 hour using subsurface buoysystem at a depth at 2,257m on the southeast off of Minami-torishima island, Japan have been analyzed. The results show the existence of Ekman layer in May. During this month, Ekman layer thickness and eddy viscosity are estimated using the angle between 3m and 5m above the sea bottom as follows; Ekman layer thickness: 4.4～7.4m; Eddy viscosity: 0.5～1.4cm＾2/sec

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Bio-logging technology has started from using mechanical Time Depth Recorder (TDR) to measure simply dive depth and duration of marine mammals and birds. However recently it has remarkably advanced as highly sophisticated animal borne observation system. Digital electronic technology enabled us to develop highly sophisticated small data logger system by which we could obtain integrated information on animal behavior, ecology, physiology and environment from underwater, which are still invisible and inaccessible for us. Now we are able to add more ocean observation sensors to the system such as optical sensors, and much more integrated in formation on not only animals but also whole ocean phenomena will be obtained, which will bring us new knowledge about ocean.

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One of the most interesting and challenging mysteries in the fish biology is the homing mechanism of salmon to migrate long distances from the open water to their natal river for spawning, but there are still many unknowns because the lack of a suitable model system to fol low their whole life cycles, especially during the oceanic migration. In addition to chum salmon (Oncorhynchus keta) that migrate from the north Pacific Ocean to Hokkaido, lacustrine sockeye salmon (O. nerka) and masu salmon (O. masou) in Lake Toya, Hokkaido, Japan, where the lake serves as a model ”ocean”, offer good model systems for studying the physiological mechanisms of the homing migration in salmon. Three biotelemetry instruments (ultrasonic transmitter, electromyographic radiotransmitter, and micro-datalogger) have been applied to investigate the homing behaviors of mature chum, sockeye, and masu salmon. Since each instrument has great advantages and/or minor disadvantages, we are developing an automatic salmon-tracking robot boat consisting interrelated four equipment systems; a robot boat, an ultrasonic tracking system, a signal processing and control system, and a telecommunication system between a land base and the robot boat. These new biotelemetry technologies make it possible to clarify the physio logical mechanisms of the homing migration.

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We evaluated the pop-up archival tag data obtained from an adult Pacific bluefin tuna, com paring with the ultrasonic transmitter data of the same tuna. The tag was designed to measure light intensity every two minutes for estimation of daily tag geolocation and ambient tempera ture every one hour. The tag was released from the fish and surfaced at a predetermined date and downloaded data recorded while on the fish via the Argos satellite system. The nine tag geolocation data showed the biases of easterly 1.10 ± 1.46 (mean ± SD) degree and southerly 1.24 ± 3.85 degree from the positions determined by the GPS during tracking of the transmit ter. The geolocation errors were mainly attributed to the vertical migration of the bluefin tuna around sunset and sunrise. The quick upward and downward behavior also affected the ambient temperature data. Despite of these disadvantages, the pop-up tags have value in use for monitor ing basin-scale movement of larger fish like tuna because of their advantage that the recapture of the tags is not needed.

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Mekong giant catfish Pangasianodon gigas is endemic to Mekong River basin and endangered species. It is urgently necessary to learn more about the movement pattern of the catfish to con serve. We started the Mekong giant Catfish Tracking Project (MCTP) in 2001, which is ecologi cal research cooperatived with Thai government. The horizontal and vertical movements of the catfish were measured by ultrasonic depth-sensitive transmitters in the reservoir. Temperature of both the surface layer and bottom, and depth-temperature profile were surveyed using depthtemperature data loggers. The catfish appeared to favor relatively deeper areas horizontally and spent the majority of their time above the thermocline vertically. The catfish exhibited the as cent to the surface at dusk and the descent to the thermocline at dawn in the reservoir. Diel movement patterns of the catfish may be related to the foraging behavior.

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Multi-data sampling on free-ranging animals appears as a valuable tool to investigate under water behavior in relation to environmental features. Using digital cameras and data loggers, diving behavior of free-ranging Weddell seal (Leptonychotes weddellii) mothers was monitored. Field experiments were conducted from November to December of 1999 and 2000 at breeding colonies in Antarctica. Weddell seal mothers showed two patterns of dive behavior: deep dives for foraging and shallow dives for socializing with their pup. Deep foraging dives were analyzed using image data and three-dimensional (3D) dive paths to address the 3D nature of the inter actions between Weddell seals and their prey at the spatial and temporal scales relevant to an individual predator. The recorded images showed that seals encountered prey-like objects at the depths of 250-300 m. The seals' 3D dive paths were affected by the location of breathing holes in the ice and the slope of local bathymetric features.

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Acoustic observation is well-known to be an effective method to detect calls of marine mam mals. We applied this method to observe calls of dugong, Dugong dugon, which has become highly endangered in the world. In this study, we described the technique to detect the arrival direction and the acoustical characteristics of dugong calls. These aspects are needed in design ing the observational equipments. In addition, specifications for an innovative observational de vice were described. A number of dugong calls were recorded around Libong Island, Trang province in Thailand, using two sets of dual channel stereo hydrophones on two research ves sels. The center frequency of dugong calls ranged between about 3 and 8 kHz, and the duration of the calls was classified roughly in two: 100-500ms and over 1000ms. Vocalization interval was classified in two patterns: 0-5s and 20- s between each call. We applied the phase differ ence analysis to dugong calls in order to calculate the arrival direction at the research vessels. These preliminary results suggested that the acoustical analyses on the dugong calls are a pow erful method to locate the vocalizing dugongs without any impact on them at all.

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