Disappearance of a spring cohort in a population of the dragonet,Repomucenus valenciennei, with spring and autumn spawning peaks in Tokyo Bay, Japan

1999 ◽  
Vol 46 (4) ◽  
pp. 331-339 ◽  
Author(s):  
Kou Ikejima ◽  
Makoto Shimizu
Keyword(s):  
Tokyo Bay ◽  
Repomucenus Valenciennei

Production of asari (Manila) clams, Ruditapes philippinarum, during the period of harvest decrease in the 2000s in the Banzu tidal area, Tokyo Bay

2020 ◽  
Vol 33 ◽  
pp. 14
Author(s):  
Mitsuharu Toba ◽  
Jun Kakino ◽  
Kazuo Tada ◽  
Yutaka Kobayashi ◽  
Hideharu Tsuchie
Keyword(s):  
Field Investigation ◽  
Ruditapes Philippinarum ◽  
Management Style ◽  
Seed Stock ◽  
Tokyo Bay ◽  
Yearly Variation ◽  
Culture Area ◽  
Stock Biomass ◽  
Tidal Area ◽  
High Level

In Tokyo Bay, the harvestable quantity of asari (Manila) clams Ruditapes philippinarum has been decreasing since the late 1990s. We conducted a field investigation on clam density in the Banzu culture area from April 1988 to December 2014 and collected records spanning January 1986 to September 2017 from relevant fisheries cooperative associations to clarify the relationship between the temporal variation in stock abundance and the production activities of fishermen. The yearly variation in clam abundance over the study period was marked by larger decreases in the numbers of larger clams. A large quantity of juvenile clams, beyond the biological productivity of the culture area, may have been introduced as seed stock in the late 1980s despite the high level of harvestable stock. The declines in harvested quantity began in the late 1990s and may have been caused by decreases in harvestable stock despite the continuous addition of seed stock clams. The harvested quantity is likely to be significantly dependent upon the wild clam population, even within the culture area, as the harvestable quantity was not correlated with the quantity of seed stock introduced during the study period. These declines in harvested quantity may have resulted from a decreasing number of operating harvesters due to the low level of harvestable stock and consequently reduced profitability. Two findings were emphasized. A certain management style, based on predictions of the contributions of wild and introduced clams to future stock biomass, is essential for economically-feasible culturing. In areas with less harvestable stock, actions should be taken to maintain the incomes of harvesters while avoiding overexploitation, even if the total harvest quantity decreases.

MEASURES FOR ENVIRONMENT CONSERVATION IN ENCLOSED COASTAL SEAS

2017 ◽  
Author(s):  
Keizo Negi ◽  
Keizo Negi ◽  
Takuya Ishikawa ◽  
Takuya Ishikawa ◽  
Kenichiro Iba ◽  
...  
Keyword(s):  
Water Pollution ◽  
Water Quality ◽  
Water Mass ◽  
Sea Water ◽  
Red Tide ◽  
Water Environment ◽  
Quality Standard ◽  
Tokyo Bay ◽  
View Point ◽  
High Concentration

Japan experienced serious water pollution during the period of high economic growth in 1960s. It was also the period that we had such damages to human health, fishery and living conditions due to red tide as much of chemicals, organic materials and the like flowing into the seas along the growing population and industries in the coastal areas. Notable in those days was the issues of environment conservation in the enclosed coastal seas where pollutants were prone to accumulate inside due to low level of water circulation, resulting in the issues including red tide and oxygen-deficient water mass. In responding to these issues, we implemented countermeasures like effluent control with the Water Pollution Control Law and improvement/expansion of sewage facilities. In the extensive enclosed coastal seas of Tokyo Bay, Ise Bay and the Seto Inland Sea, the three areas of high concentration of population, we implemented water quality total reduction in seven terms from 1979, reducing the total quantities of pollutant load of COD, TN and TP. Sea water quality hence has been on an improvement trend as a whole along the steady reduction of pollutants from the land. We however recognize that there are differences in improvement by sea area such as red tide and oxygen-deficient water mass continue to occur in some areas. Meanwhile, it has been pointed out that bio-diversity and bio-productivity should be secured through conservation/creation of tidal flats and seaweed beds in the view point of “Bountiful Sea” To work at these challenges, through the studies depending on the circumstances of the water environment in the enclosed coastal seas, we composed “The Policy of Desirable State of 8th TPLCS” in 2015. We have also added the sediment DO into the water quality standard related to the life-environmental items in view of the preservation of aquatic creatures in the enclosed water areas. Important from now on, along the Policy, is to proceed with necessary measures to improve water quality with good considerations of differences by area in the view point of “Beautiful and bountiful Sea”.

scholarly journals Development of training method for vessel traffic service based on cognitive process

2021 ◽  
Author(s):  
Binbing Song ◽  
Hiroko Itoh ◽  
Yasumi Kawamura
Keyword(s):  
Cognitive Processes ◽  
Cognitive Process ◽  
Process Model ◽  
Situational Awareness ◽  
International Association ◽  
Tokyo Bay ◽  
Training Methods ◽  
Training Method ◽  
Oral Transmission ◽  
Maritime Traffic

AbstractVessel traffic service (VTS) is important to protect the safety of maritime traffic. Along with the expansion of monitoring area per VTS operator in Tokyo Bay, Japan, inexperienced operators must acquire the ability to quickly and accurately detect conditions that requires attention (CRAs) from a monitoring screen. In our previous study (Song B, Itoh H, Kawamura Y, Fukuto J (2018) Analysis of Cognitive Processes of Operators of Vessel Traffic Service. In: Proceedings of the 2018 International Association of Institutes of Navigation. IAIN 2018, pp 529–534, Song et al., J Jpn Inst Navig 140:48–54, 2019), we established a task analysis method based on the assumption that the cognitive process model consists of three stages: “situational awareness”, “situation judgment”, and “decision making”. A simulation experiment was conducted for VTS operators with different levels of ability and their cognitive processes were compared based on the observation of eye movements. The results showed that the inexperienced operators’ abilities to predict situation changes were lower. And it was considered that oral transmission of the knowledge is difficult, thus new training methods are needed to help the inexperienced operators to understand the prediction methods of experienced operators. In this study, based on the cognitive process of an experienced operator, we analyzed the prediction procedures of situation changes and developed an educational tool called vessel traffic routine (VTR). The training method learning VTR aims to quickly improve inexperienced VTS operators’ abilities to predict situation changes. A simulation verification experiment of the VTR effect was conducted for four inexperienced operators, who were divided into two groups with and without prior explanation of VTR. By evaluating the cognitive processes of inexperienced operators, it was confirmed that those given prior explanations of VTR were better at detecting CRAs.

Qualitative Discussion of Influences of some Factors on the Occurrence of Wind-Driven Coastal Upwelling Associated with “Aoshio” on the Northeast Shore of Tokyo Bay Using the Developed Analytical Model

2014 ◽  
Vol 641-642 ◽  
pp. 1040-1045
Author(s):  
Zhong Fan Zhu
Keyword(s):  
Analytical Model ◽  
Wind Shear ◽  
Coastal Upwelling ◽  
Tokyo Bay ◽  
Interfacial Friction ◽  
Observation Data ◽  
Shear Effect ◽  
Stratification Effect ◽  
Northeasterly Wind ◽  
Qualitative Discussion

An analytical model based on some solutions in the context of a two-layered fluid was developed to estimate the occurrence of northeasterly wind-driven coastal upwelling associated with “Aoshio” on the northeast shore of Tokyo Bay, and its validity was verified by comparing with observation data [1]. In this study, influences of all of the factors incorporated into this analytical model (including densities and thicknesses of the upper and lower layers, the parameter expressing the influences of interfacial friction and bottom friction) on the model are analyzed. The analytical model is found to express the competition between the wind-shear effect and the stratification effect: when the former dominates over the latter, Aoshio will occur on the northeast shore of the bay. The parameter that can be used to characterize the stratification effect can be simply expressed in terms of the product of density contrast and the square of thickness of the upper layer. Using different values of this parameter corresponding to different months in the model can simply estimate in which months it is easy for Aoshio phenomenon to happen on the northeast shore of the bay, and the result is roughly consistent with an observation phenomenon that Aoshio was frequently observed on the northeast shore of the bay in September and May and relatively less observed in June and July during 1978-2010.

scholarly journals Sediment Oxygen Consumption and Microbial Community Structure in Tokyo Bay

2010 ◽  
Vol 66 (1) ◽  
pp. 1036-1040 ◽  
Author(s):  
Masanori ENDO ◽  
Yukio KOIBUCHI ◽  
Masafumi FUJITA ◽  
Jumpei SUZUKI ◽  
Hisako OGURA ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Community Structure ◽  
Microbial Community ◽  
Microbial Community Structure ◽  
Tokyo Bay ◽  
Sediment Oxygen Consumption
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