A behavioural model of Conger myriaster in Ise Bay is developed which considers the migration effect as well as the growth and the population change. The model is coupled with a hydrodynamic model and a lower-trophic ecosystem model which predict physical environment and water qualities of the target area. In the migration model, the direction of the fish movement is determined by the preference intensities for the environmental factors such as water temperature, dissolved oxygen, and so on. The fish growth is expressed by Von Bertalanffy's formula, parameters of which are tuned so that the formula represents the actual fish size variation. The population change is calculated by a general population dynamics model, in which the fishing mortality is estimated by the actual fish catch data. The model is validated by comparing the annual change of fish catches at major fishing ports. The results of the fish behaviour simulation showed that the areas with high resource density in the simulation corresponded to high CPUE areas in the real world. The relation of environmental factors and fish dynamics, and the situation of resource utilization are also discussed.
There are some sea caldrons in Seto Inland Sea, Japan, whose bottom is formed by muddy sediment and thus which has low productivity of fisheries. A construction of fishing ground by filling the caldrons is proposed as one of the countermeasures. It is necessary to estimate the effect of the construction on aquatic species around new fishing ground. Thus an environmental assessment is conducted by using numerical hydrodynamic model and Habitat Evaluation Procedure (HEP) in order to evaluate the effect on habitats for Branchiostoma japonicum, which is living around the new fishing ground and is also academically valuable. Using a multi-level density flow model, tidal currents before and after filling the caldron are firstly simulated. Then, using resultant flow field, the distribution of maximum resuspended particle sizes on the sea bottom is estimated based on the threshold of sediment movement. Habitat Suitability Index (HSI) is developed for the evaluation of habitat environment for Branchiostoma japonicum. Based on earlier studies and field observations, the median particle diameter and mud content of the sea bed are employed for calculating values of SI, and then HSI is calculated as a geometric mean of SIs. The results show that the values of HSI in the habitats after the construction are equal or larger than those before the construction.
The tsunami that followed the Great East Japan Earthquake caused massive damage to the fishing port facilities. This study introduced the damage conditions and patterns of breakwaters and quay wall of fishing port based on the field survey. Furthermore, based on the hydraulic experiments, i) tsunami wave pressure acting to the breakwater on overflowing condition, ii) characteristics of lift force on waveabsorbing type quay by tsunami and iii) evaluation of required mass of stable armor units for tsunami were investigated to develop the tsunami resistant design for the fishing port facilities.
Placement of protection mounds at the rear-side of breakwaters is one measure for increasing the resistance of the fishing port breakwaters against tsunami. Placement of concrete blocks are necessary to prevent the mounds from scouring due to the overflow of tsunami. Establishment of a practical design method for concrete blocks covering protection mounds of fishing port breakwaters against tsunami overflow is an urgent issue. In this report, two existing design methods, namely, a velocity based method and an overflow depth based method, are reviewed. The influences of the rear-side waver level and the block shape on the armor stability are discussed by using the experimental results. Numerical analysis is conducted to reveal the failure mechanism of the blocks. The activity of the Association for Innovative Technology on Fishing Ports and Grounds is also reported. Hydraulic model experiments were conducted in this activity to determine the stability number for each concrete block and these are used to calculate the required mass of the block against tsunami overflow.
The structure of a "tenacious" breakwater is required from the Great East Japan Earthquake in 2011. The widening work is one of existing reinforcement methods of tenacious breakwaters. However, it also has large cross section in port inside area. Furthermore, scouring due to the overflow decreases the bearing capacity of the rubble mound and it makes the breakwater easy to fall down. In "Tsunami-Resistant Design Guideline for breakwaters", by Ministry of Land, Infrastructure and Transport, the widening work is described, on the other hand, the reinforcing method to resist tsunami with steel pipe piles is proposed too. Therefore, we developed the reinforced method of a tenacious breakwater with steel pipe piles. The breakwater has filling stones between the caisson and the steel pipe piles, and it can resist a tsunami tenaciously. We call the method "Steel Pipe method".
In Hirono town, Iwate prefecture, the wave-cut bench area which was above sea level only at low tide was developed to nursery for abalone and sea urchin. As a result of the promotion of sea farming, the nursery has become major source of income in the town. However, the nursery was seriously damaged by the Great East Japan Earthquake and Tsunami. Sea urchin is one of the specialties of the town. Therefore, all the parties concerned made efforts to restart of sea urchin farming in nursery. By their efforts, 1) the restoration of the nursery, 2) the restart of sea urchin transplantation and fishing, 3) the restart of seedling production of juvenile sea urchin and 4) the restart of sea urchin direct-sales had been done in some months after the earthquake. Now, it passed for 3 years and 10 mounts after the earthquake. Restart of nursery in Hirono town went well. However, we still have some problems. For example, finding un-recovered areas and recovering abalone and sea urchin resources will take some years. Ageing and depopulation of local fishermen are also the problems. To assess the influence of the earthquake early, monitoring is effective. It is necessity to continue the survey for assessment of recovery from damages of the earthquake.
There is little information about the physical properties of gravel beaches habitats for organism. In order to elucidate whether the physical properties in shoreline areas of gravel and sand beaches, how differences in, the saturation level using glass beads gravel equivalent particle size was measured by suction. Also, the sediment hardness was measured using four different measuring instruments, in order to understand the basic physical properties in shoreline areas of gravel beaches. Suction, which increases as the particle size is smaller, the value was small. Also, in the unsaturated state, the saturation level has a substantially constant value vary. 4 kinds of hardness index, increased as the particle size became large, in the unsaturated state, and was almost constant regardless of the saturation level. From these results, the particle size of the gravel equivalent is estimated to be nearly physical properties with saturated, unsaturated and particle size (weight of one grain) is determined, and the value of the suction and sediment hardness due to the variation of the saturation level effects of variation was small.
In this study, the relationship of tidal changes on a sandy coast, and emergence and distribution of sand burrowing an isopod and amphipod was examined over tidal cycles. As a result, the sand burrowing an isopod and amphipod that appeared in this study, moved from the initial fixed point of emergence to offshore as the tide falls. In addition, when the gradient of the shore becomes gentle, distribution area is spread, density fell. Generation point of sand ripples are fixed without moving to the offshore side. These results zonation sand burrowing small crustaceans in sandy coastal shoreline areas is according to the findings of the Sea of Japan (Fluctuations in the suction of change and sediment environment associated with it, Changes in littoral drift behavior typified by the generation of sand ripple and step), variations in tide became clear that affect within the range.
The Award of the Japanese Society of Fisheries Engineering was given for the studies on ecology and restoration of seagrass・seaweed bed along the coast of Japan from the view on Fisheries Engineering. This study is made up of three parts. The first is for methods of submarine forest formation considering local limiting factors of distribution. The second is for seaspace features of "Isoyake area" in southwest Japan. The third is for excellent examples of eelgrass Zostera marina bed restoration continuing along the coast of Seto Inland Sea, Japan. In this paper, outline of contents on the awardee lecture in 30th May 2015 Meeting in Nagasaki were noted.
To understand the capture process of different types of fishing gear, and to design the gear and aquaculture facility to improve the efficiency of fish production, it is important to obtain data on fish behaviour regarding their response to the fishing gear and aquaculture facilities used. There have been a number of research studies on the dynamics and catching capability of fishing gear. On the other hand, owing to the behavioural measurements in fisheries research, and the appearance of biotelemetry and bio-logging technologies, it has become possible to determine the behaviour of fish near/within the vicinity of fishing gear and in an aquaculture facility. To obtain a scientific understanding of the response of fish to fishing gear and aquaculture facilities, it is necessary to detect the position of the target fish to confirm its specific positional relationship with the fishing gear and aquaculture net cage. This paper introduces behavioural measurements using biotelemetry, bio-logging, and video analyses established by the author that can be used to detect the position of a fish for fisheries and aquaculture research. It is believed that these behavioural measurement techniques will be useful for fisheries engineering as a new biological approach.