日本水産工学会誌
Online ISSN : 2189-7131
Print ISSN : 0916-7617
ISSN-L : 0916-7617
52 巻 , 3 号
選択された号の論文の12件中1~12を表示しています
  • 志田 崇, 藤川 義一, 石川 義朗, 今 男人, 桐原 慎二
    2016 年 52 巻 3 号 p. 161-170
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    Seagrass beds are widely distributed in the coast of Aomori prefecture. Seagrass beds serves as fishing ground of the sea cucumber in Mutsu-bay. The artificial shelter was developed for growing both sea cucumber and seagrass with together. Experiment using the artificial shelter was done in the coast of the Mutsu Bay during several months, and the growth of seagrass Zostera caespitosa and japanese common sea cucumber Apostichopus japonicus were observed around artificial shelter. Natural and transplanted seagrass were collected and increasing in growth rates of each organism was confirmed when they were together in the shelter. These results showed the artificial shelter was effective for the increase of seagrass and sea cucumber resources.
  • 江幡 恵吾, 小川 真一郎, 不破 茂, 藤田 伸二, 北野 潔
    2016 年 52 巻 3 号 p. 171-176
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    A fish aggregating device(FAD) is a floating construction installed at sea to attract and aggregate fish. Fishermen conduct an operation of troll lines to catch tuna and skipjack tuna in areas around FADs in southern Japan. It is very dangerous to catch fish near FADs because FADs are moving objects and can collide with fishing boats. Model experiments using a 1/30 model (length 25.0 cm, width 13.0 cm, and height 11.7 cm) were carried out in a flume tank. The movements of the FAD were recorded in top view using a digital video camera. Video images were converted into static images every 1/30 seconds to measure the periods and the distances of the movement of FAD. The flow speed was changed from 9.4 cm/s (1.0 knot) to 28.8 cm/s( 3.0 knots). 8 different size of boards were constructed and installed on the stern side to reduce the movement of the FAD. Amplitude of the movement of the FAD was reduced by installing a rectangular board at the bottom of the stern.
  • 尾形 梨恵, 高木 康次, 御宿 昭彦, 藤田 大介
    2016 年 52 巻 3 号 p. 177-184
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    Restoration of a Sargassum forest was challenged at an enclosed block (10×10 m) on Diadema barren in Uchiura Bay, on the northwest coast of Izu Peninsula, Shizuoka Prefecture. In the block, Diadema was monthly removed and invasion of Diadema was prevented by deploying fences( rolled gill nets). To introduce a mass of Sargassum embryos, thalli of S. piluliferum were installed in the suspended net ( 1.5×3m ) laid at a height of 1 m from the bottom( 4 m in depth) in April and May 2009 and May 2010. In 2009, transplanted thalli of S. piluliferum matured in June;hundreds of juveniles (less than 2cm in height) appeared in August. Although Diadema invaded the block and consumed most of the juveniles before deployment of the outer fences, 20 juveniles survived and grew rapidly on the cobbles covered with small macroalgae. The juveniles grew up to 60 cm in average (180 cm at maximum) in height in May 2010. Although the canopy disappeared in September, juveniles appeared in January. Monthly average of water temperature ranged between 13.7℃ in March and 24.5℃ in August in 2009. In 2010, however, transplanted thalli of S. piluliferum failed in maturation. The higher water temperature (from 14.2 in February to 27.8℃ in August) may inhibit its maturation.
  • 磯野 良介, 島 隆夫, 渡邉 幸彦, 長谷川 一幸, 馬場 将輔
    2016 年 52 巻 3 号 p. 185-187
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    Feeding rate of brown algae Siganus fuscescens reared on rabbitfish Eisenia bicyclis for 17 days at 26 and 29℃ were 32.20% of body weight( BW) /day and 39.05% BW/day. Specific growth rate( SGR) at 26 and 29℃ was 51% and 70% of fish fed commercial dry pellet 2.5% BW/day, respectively. It is considered that S. fuscescens has the ability to utilize nutrients of E. bicyclis, although a large amount of alga would be required to enable growth due to its poor nutritional value.
  • 松下 吉樹
    2016 年 52 巻 3 号 p. 189-195
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    Squid jigging with fish attraction lamps is a selective fishing method that produce high quality squids, but considered to consume large amount of fuel. To secure the profitability of this fishing by reducing energy consumption, we need to perform an energy audit of squid jigging boat. Amount of fuel consumed and landing value for 34 boats of 19-ton class in Nagasaki showed a strong linear-relationship, but its slope was smaller than the past relationship due to a rise of fuel price and installation of more lamps. Voluntary regulated maximum electrical output for lighting for boats operating in a coastal area of Nagasaki has increased to approximately 20 times in 20 years while catch amount has increased to 2-3 times. Thus, excessive use of fuel for lighting power competition has gradually caused difficulty to keep a catch level that is appropriate to the invested value. Fuel consumption in operation processes such as fishing with light and cruising was investigated with considering energy management structure of squid jigging boats. All boats consumed the largest amount of fuel during fishing with light and the amounts consumed were expressed by a linear relationship that was proportional to amounts of electricity used by boat sizes. Fuel saving during cruising process was however efficient in some cases because fuel consumption in operation processes were different by fishing areas and seasons.
  • 四方 崇文
    2016 年 52 巻 3 号 p. 197-203
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    In order to elucidate the process of gathering and capture of Japanese common squid Todarodes pacificus, night-time squid jigging operations were conducted by R/V Hakusan-maru (167 gross tons) equipped with 78 metal halide lamps( 234 kW in total) in the Sea of Japan. The behavior of the squid and the changes in catch per unit effort( CPUE) and density of the squid under the vessel were investigated during each operation. The following results and conclusions were obtained: (1) Squid schools moved around the high-irradiance area formed along port and starboard side of the vessel, and tended to locate in fore and aft areas just before they were caught. Therefore, fore and aft areas with low irradiance are thought to function as an entrance to the shaded area under the vessel for the squid.( 2) When the shaded area was eliminated and deformed by lighting of underwater lamp, the squid moved away from the area under the vessel and CPUE decreased. Thereafter, when the underwater lamp was turned off, the squid immediately gathered under the vessel and CPUE increased. These results indicate that the shaded area is essential for gathering the squid under the vessel and capturing them. (3) CPUE increased with increasing squid density, but the extent of the increase of CPUE greatly differed by operation. When CPUE was extremely high, the increase of CPUE slowed down. The relationship between CPUE and squid density (S) was expressed as CPUE=A・S/(B− 1+S), where A is an upper limiting CPUE and B is catchability of the squid. Furthermore, B was found to vary greatly among operations. For this reason, it was thought that higher squid density does not necessarily bring about more catch.
  • 髙山 剛
    2016 年 52 巻 3 号 p. 205-208
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    Squid jigging fisheries in Japan using fishing lights require large amounts of electric power. To improve energy efficiency, the methodology of this fisheries should be reconstructed through understanding capture processes, but most of capture process of squid jigging remain unknown. In this study, the capture process of this fisheries was discussed based on behavioral experiments and observations of fishing lights by underwater camera.   Results of behavioral experiments indicate that squid responded to the light direction rather than the light intensity. They oriented to light from a horizontal direction, moved toward the light source and remained in the environment where light was coming from above them. Underwater observations showed that far from the boat, the light from fishing lamps reached the camera from a horizontal direction, while nearby the boat, the light reached the camera almost vertically.   From these results, it is considered that the fishing lights of squid jigging boats have two functions. The first is to lead squid toward the boat from a wide area, and the second is to retain the squid under the boat. When improving the fishing light system, arrangement of light source should be planned so as not to impair these functions.
  • 髙橋 晃介, 阿保 純一, 貞安 一廣, 谷口 皆人, 平野 満隆, 髙山 剛, 山下 秀幸
    2016 年 52 巻 3 号 p. 209-215
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    The squid jigging fisheries consume a large amount of fuel for illumination by using conventional metal halide lamps( MH), which reduce a profit due to the rise in fuel price. Light emitting diode( LED) lamps have been proposed as a way to achieve energy savings in jigging fisheries. We compared the catch performance of squid jigging vessels that use either the MH or the LED lamps. For comparison, we adjusted the number of the MH lamps to have the same irradiance of the LED. We investigated irradiance and its distribution around vessels for both the LED and the MH lamps at the port and also by a numerical simulation. Both methods showed the equivalent irradiance distribution. CPUE of operations using LED was 91% of the CPUE of operations when number of MH lamps were reduced to have a same irradiance at the sea-surface where 50 m away from the wheelhouse of the vessel. When MH lamps were reduced to have not only irradiance but also its distribution around the vessel, CPUE of using LED was 93% of CPUE using MH.
  • 田丸 修
    2016 年 52 巻 3 号 p. 217-222
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    In recent years,both of fuel price increase and fish price decrease are giving serious economic damage to Japanese fishermen’s management. Especially,the coastal squid jigging fishery requires much fuel for the long distances cruise and the high powered fishing lamps. The fishermen usually decide their behavior of fisheries operation based on their own knowledge and experience. We considered the simulation study may help fishermen to make optimum decision in the behavior of fisheries and contribute to profit maximization. We conducted the simulation for fishery profit maximization including various factors of the squid jigging fishery,and showed that the profits are very sensitive to several factors such as fish prices,fuel prices,the distances from the ports to the fishing grounds,and the ship speeds. We concluded that development of the simulation study would contribute to optimization of fishermen’s behavior and to maximization of the profits near future.
  • 古原 和明
    2016 年 52 巻 3 号 p. 223-225
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    Squid jigging fishery is one of the key fisheries in Nagasaki Prefecture. This fishery consumes large amount of fuel for the lighting in the nighttime and its high cost has impacted on the financial situation. To improve this condition through the reduction of fuel cost, Nagasaki Prefectural government proposed to reduce the upper limit of lighting power in the voluntary regulation of the Nagasaki squid fishermenʼs council from 160 kW to 120 kW in 2014. Some fishermen however objected to this proposal, so that following plans are under consideration now. 1. To request the relevant organizations to set the 120 kW maximum lighting power in their voluntary regulations, which have an effect all over Japan. 2. To set the voluntary rule in Nagasaki that promotes energy efficient fishing practices such as slow speed navigation to/from fishing ground and fishing with the stage reduced lighting procedure.
  • 串崎 康文, 松下 吉樹
    2016 年 52 巻 3 号 p. 227-231
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    The first author has been operating a squid jig fishing in Tsushima Island, Nagasaki for approximately 30 years since 1980's. Squid jigging fishery has experienced the stagnant squid prices after the asset bubble burst, the lighting power competition among the boats to increase catch amounts and a rise in fossil fuel prices during those 30 years. Consequently, the business performance of squid jigging fishery has deteriorated. We present the fishermenʼs perspective on how the squid jigging fishery should survive in the present condition; 1. combination of fishing practices that operate energy intensive squid jig fishing and energy saving (but labor intensive) longline fishing by considering the cost and benefit properly, and 2. rationalization of squid jig fishing through recent technical improvement such as a use of scanning-sonar and an introduction of fishing lamp consisting of low energy light emitting diodes.
  • 山下 秀幸, 越智 洋介, 高橋 晃介, 大久保 照享, 田添 伸
    2016 年 52 巻 3 号 p. 233-237
    発行日: 2016年
    公開日: 2016/09/01
    ジャーナル オープンアクセス
    The symposium “Discussion among Industry-Government-Academia on Rationalization of squid jigging fisheries at night time.” was held in the annual meeting of the Japanese Society of Fisheries Engineering in May 2015. At the symposium, participants of scientists, fishermen and government administrators made presentations and discussions from the following viewpoints; i.e. the current business environment and problems on the fisheries; clarifications of the fishing operation processes and functions of the fishing light; the progress of LED fishing light development as an energy-saving device; and approaches to improving the profitability of the fisheries.   The discussions are summarized as follows. An energy saving of the fishing lamps, especially by using the LED, is one of the most important approaches on rationalization of the fisheries. It also contributes to reduction of CO2 emissions as the international expectations. For this purpose, equalizing the light condition of LED fishing light to metal halide fishing light should be the first step. Then, an optimization of the characteristics of fishing lamps such as adequate range of wavelengths of light and its distribution that is appropriate both to the behavioral characteristics of squid and the functions of the LED light source, would be required in the next step. In addition to those, the visualization of the energy usage structures on the fisheries to optimize the energy consumption is necessary. To promote the above-mentioned approaches, the consensus-building to avoid the excessive light power competition among fishermen is necessary to realize a reduction in total energy consumption. We must continue these approaches with an industry-government-academia cooperation.
feedback
Top