2006 Fiscal Year Final Research Report Summary
Studies on development of a multiple opening/closing frame trawl for sampling larval and juvenile fish
| Project/Area Number |
17580159
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Tokyo University of Marine Science and Technology |
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Principal Investigator |
HU Fuxiang Tokyo University of Marine Science and Technology, Faculty of Marine Science, Associate Professor, 海洋科学部, 助教授 (80293091)
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| Co-Investigator(Kenkyū-buntansha) |
TOKAI Tadashi Tokyo University of Marine Science and Technology, Faculty of Marine Science, Professor, 海洋科学部, 教授 (30237044)
SHIODE Daisuke Tokyo University of Marine Science and Technology, Faculty of Marine Science, Assistant Professor, 海洋科学部, 助手 (40361810)
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| Project Period (FY) |
2005 – 2006
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| Keywords | larval and juvenile / quantitative collection / estimation of stock abundance / frame trawl / automatic opening / closing / net-frame inclination control / net mouth / cod-end |
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| Research Abstract |
In order to continuously utilize the fisheries resource effectively, it is necessary to estimate the stock abundance of the target fish species accurately. The quantitative collection of the larval and juvenile is pointed out as one of the means. In this research, the new multi-sampling trawls with automatic net-mouth/cod-end opening and closing control system were developed based on the MOHT frame trawl. The results are shown as follows.
1)A new multi-sampling trawl with automatic net-mouth opening and closing control system was developed. It has a rigid-framed of 1.9m x 1.8m on the net mouth and four bag nets of 12.8m long. The net-release controller and battery unit are installed to the bottom of the frame. The memory card inserted in the controller not only controls the motor for the net-opening/closing mechanism, but also records net depth, temperature and filtered volume during the net towing. The command from the memory card open and close four bag nets sequentially at a depth se
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t and/or on time set without any command from the surface through conducting cable or acoustic signal. The flume tank test with 1/3-scaled model and sea trial with the prototype were conducted to investigate the performances of automatic net-opening/closing control system as well as the towing characteristics. From the two experimental results, the frame leaned forward at angle from 5 to 10 degree under several towing speeds ranging from 2 to 4kt, and the tilt angles allow the net bar to drop smoothly. It is confirmed that the dropping bar freely fallen smoothly and then the next net mouth was opened completely when the trigger was released by the command from the controller. In addition, even while the towing speed increasing/decreasing, the change in net depth was extremely small.
2)In this fiscal year, another multi-sampling trawl for opening/closing the cod-end was also developed. It has a rigid net-mouth frame and five cod-ends. The automatic opening/closing device is installed between the front net and cod-ends. The field experiment was carried out using training ship "Hiyodori" of Tokyo University of Marine Science and Technology in the Tateyama bay. From the results, the net maintained almost constant depth under towing speed from 2.0-4.5kt, and the net-mouth frame maintained upright position, similar to the frame sampler MOHT. We have also confirmed that the cod-ends were surely opened/closed smoothly by the command from the controller that was installed to the bottom of net-mouth frame.
As mentioned above, in this research, the purpose was achieved and the developed gears can be towed at high speed to collect larval and juvenile fish quantitatively in the target depth. The spread as the standard gear for resource investigation will be expected in the future. Less
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Research Products
(2 results)
