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.
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
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
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.
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.
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
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.
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.
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
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.
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.
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.
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.
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.