中型まき網漁業の灯船のスキャニングソナー画像を解析して，魚群反応の画素数から漁獲結果を予測する実験式を得た。この式を用いて集魚中の魚群にした場合に期待される漁獲量（期待漁獲量）を算出し，しなかったときの期待漁獲量を比較したところ，期待漁獲量の増加とともにする確率が高くなった。漁労長は期待漁獲量が 1.5 トン以上の集魚で必ずし，50% の確率でを行う期待漁獲量は 1.3 トンであった。期待漁獲量が 1.3 トンと 1.5 トン以上の集魚回数はそれぞれ全体の 32% と 24% であった。

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Small trawl fishing is an important fishery that supplies a variety of fishery products to the market. The fishing operations are usually carried out in coastal seas. In this study, the authors focused on beam-type small trawl fishing boats in the northern coastal seas of Kyushu. And we conducted a survey about the operating methods and the labor-saving effects by use of fishery machines. By the use of the trawl winch, the shooting net time was shortened compared to the conventional method. Furthermore, applying the OWAS method for the physical burden of skipper, the labor-saving effects are confirmed on net shooting and hauling operations.

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Osaka bay is very congested area, since many fishing vessels catch fishes, and many ferries and freighters come and go. In order to prevent maritime accidents, ship operators, operations managers, and pilots desire real-time positional informations about large vessels, small vessels, and fishing gears. The authors have already achieved information dissemination about positional informations of large and small vessels. However, the authors haven't acquired positional informations of fishing gears yet. The ultimate goal of this study is attaining safety and efficient navigation by providing real-time positional informations. In order to approach the goal, this paper presents an auto extraction method, which picks out the starting and finishing points of fishing using positional information of the fishing vessel. These points are very important to predict real-time positions of fishing gears. The authors focused on fishing vessels for Spanish mackerel drift net fishing, and extracted the casting start point and the hauling finish point. From evaluation results, the auto extraction method indicates the different distance less than 500 meters compared with factual starting/fishing points of fishing. This result is sufficient to achieve safety navigation.

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最終回である今回は,インドネシア共和国のスマトラ島北部に居住しているアラス族の伝統的漁法を,袋網から整理・分析していくこととする。

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  Upstream migration and distribution of freshwater fishes are investigated in the lower reach of an agricultural canal flowing into the sea. The survey on upstream migration was conducted using two fixed nets installed at the drop structure nearest to the sea and the distribution survey was carried out using a cast net and two scrape nets in the basins and downstream areas of 19 drop structures including structures of groundsill, a vertical drop, multistep drops, and an inverted drop. During the surveys, a total of 1,136 freshwater fish belonging to 4 orders, 8 families and 17 species were captured by two fix nets, a cast net and two scrape nets. The distribution survey revealed that ayu, Plecoglossus altivelis altivelis, loach, Misgurnus anguillicaudatus and Japanese dace, Triborodon hakonensis were broadly distributed within the study area. Conversely, the habitats of Ayukake, Cottus kazika and Kajika, Cottus sp. were limited to the area near the sea and the growth of these fishes were inhibited in such a simplified habitat within the concrete flume.

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The present report dealt with the shooting speed (the time needed to shoot a section of about 34m length) of 37 settings of salmon drift net each about 100 sections long in the Japan Sea by the R. V. “Hakusan-maru”. And the following results are obtained:
1. It took 8.2 to 13.4 sec to shoot a section on the string average, except the time to shoot the initial and final ends of a string.
2. The maximum retardation of shooting speed by the fore-and-aft vector of wind was estimated to be 2.3 sec/section (29°C of the time under no wind and wave), due to wind drift of boat. That by the athwartships vector was 1.5 sec/section (19°C), because the wind from star-board over some level and from port increased the possibility of sinker line tangling with cork line. And that by wind wave was 1.4 sec/section (18°C).
3. The standard deviation of shooting speed (maximum being 4.1 times of minimum), which represents irregular tautness within a string, increased with retardation in shooting speed (maximum being 1.6 times of minimum), which is one of the indicators of difficulty in smooth shooting.

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Reed belts in temperate lakes support large numbers of fishes and provide nurseries for many species, including some of endangered status or commercial importance. Although monitoring of such assemblages is important for ecological and fisheries assessments in many lakes in Japan, little information exists on appropriate sampling gear for a better representation of fish species richness and composition in reed belts. An evaluation of comparative efficiencies of different sampling methods for monitoring fish assemblages, based on six commonly used gear types [electrofishing (EF), minnow trap (MT), hand net (HN), casting net (CN), seine net (SN) and fyke net (FN)], was conducted in lentic reed belts in a eutrophic lake, Kitaura, Ibaraki Prefecture, central Japan, in June and August 2015. A total of 3,060 individuals, representing 11 families and 26 species, were collected during the study period. The mean number of species per replicate was significantly greater for FN, SN and CN than EF, MT and HN in each month. More than 96% of the total species recorded throughout the study period were collected by a combination of FN and CN. Furthermore, the species composition of the assemblages sampled by FN, SN and CN differed from that by EF, MT and HN, due to the low catch efficiency of the latter. These results suggested that use of multiple gear types, including FN and CN, represents a more efficient method for monitoring lentic reed belt ichthyofauna.

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神通川と庄川で日中に行われているアユ漁の遊漁実態を2002～2004年に調べた。両河川では友釣りなどの2つの自由漁法となどの3つの許可漁法を行う遊漁者が観察された。遊漁者数が多かった神通川では友釣りの遊漁者がその大部分を占めるとともに，その出漁努力はなどの許可漁法の遊漁者に比べ著しく高かった。友釣り，毛鉤釣り，テンカラ網およびコロコロ釣りでは，河川流量が多くなると出漁人数が減る傾向にあり，一定以上の出水時には遊漁者は認められなくなった。これに対して，では河川流量が多くなると出漁人数が増える傾向にあり，大きな出水時にも遊漁者が多く認められた。神通川に多くの遊漁者が訪れるのは，神通川の河川流量が日常的に多いこと，および良い河川形状が維持されているためと考えられた。庄川で遊漁者数を増やすには，平常時の河川流量を増加させるか，遊漁者数と出漁日数の多い友釣りの専用区を設定することが効果的と考えられた。

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In the preceding report, the authors treated of the operational limitations during scouting work, on the basis of the characteristics of ship motion, by using an actual 135 GT purse seiner working in the fishing ground. In the present paper, the main objective was shifted to the same problem during a cycle of shooting and hauling work of the net. In order to examine this problem, the process of a cycle of fishing work was classified into the six steps, and the ship motions and accelerations were measured under the four sea conditions. From the results of spectrum analysis and statistical analysis of double amplitudes relating to rolling, the probability of deck-edge immersion was estimated, and the discussion was concentrated to the change in safety with progress of fishing work under respective sea conditions. And the discussion was extended to the safety of the crew on deck during fishing work.

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The number of ayu, Plecoglossus altivelis, caught by a cast net and a tenkara (a kind of cast and gill net) at several depths was examined to clarify the effect of increasing the water depth in ayu fishing grounds in which the flow had been decreased artificially, such as in the Shou River. Ayus (mean body weight, 20 g) were caught in a concrete pond (12.4 m long, 4.5 m wide, 1.2 m high) at depths of 90 cm, 55 cm and 18 cm on 7 July, 2001. In both nets the number of ayu caught at 90 cm and 55 cm depths was significantly fewer than those caught at 18 cm depth. With a cast net, ayu caught at 90 cm depth was significantly fewer than the number caught at 55 cm depth, but with a tenkara net the number of ayu caught at 90 cm was equal to that caught at 55 cm. These differences are considered to be caused by differances in the times at which the nets reached bottom and the structure of a tenkara net of 60 cm width. The mean depth of rivers increases as the flow increases. These facts suggest that increasing the water flow or creating deeper pools artificially in such rivers as the Shou River would lead to a decrease in fishing effort for ayu and aid in propagating the ayu resources more effectively.

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このようにして養魚池で養成したウグイから採卵できるようになり, 人工ふ化, 人工餌料による椎魚の飼育ならびに親魚の養成, 人工採卵と一連の技術が完成され, 種苗生産, 河川, 湖沼への安定した放流, 養殖種苗の供給などを可能にする技術のあらすじが確立された。
今回の試験では産卵された卵は全部は採集しなかったが, 体長16.5cm位のウグイのだ卵数は約3,000粒であるから成熟♀の50%が産卵すると仮定すると10万粒を採卵するには約66尾の♀とそれとほぼ同数の♂が必要であろう。
産卵後の親魚は引続いて養成して産卵後のへい死 生殖腺の発達状態 さらに未産卵魚の産卵促進方法として新しい♂の追加放養, ホルモン剤ならびにビタミン剤の使用試験を進めている。
終りに本試験実施に当り種々御援助を受けた上田支所員ならびに校正いただいた中村所長に厚くお礼申上げる。

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As the fourth step in the experimental studies of the purse seine, a series of model experiments was made with the purpose of investigating the timely change of the depth of bottom margin of the net in the course of operation. The model gear and the experimental apparatus were the same as were used in the previous experiments^{1, 2)}. For two cases, when it took, (I), 1/2 second (about 2.1 minutes for full scale) and, (II), 1 second (about 4.2 minutes for full scale) after the net had been set into the standing water, the pursing operation was begun mechanically with a speed of 16.5cm./sec.. Then, the transformation of the net in whole course of operation was filmed with a speed of 16 pieces per second (Fig. 1).
As the results of these experiments, the relation between the depth of bottom margin of the net and the time required to attain that stage was obtained as shown in Fig. 2, from which the following facts for full scale of net were presumed;
a. For about 4 minutes (that is the second 1/4 duration of whole time (T) required to the setting and pursing) after the pursing was begun, the bottom margin of fish bag might still continue such a movement of sinking that it had done up to that time.
b. The bottom margin of fish bag may sink to the deepest depth, that is, about 60 meters (40% of the stretched depth (L) of webbing of fish bag) at about 8 minutes (1/2 stage of the whole time) after the setting was begun.
c. If the pursing is begun at 2 minutes (1/8T) after the setting was finished^*, the maximum depth to which the bottom margin reaches may increase about 10 meters (7% of L).

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On a bounds of Jyosyo, Chikuma-River, untill August, going up the season of the freshwater trouts, a fisheries productions by way of a casting net and angling are amount of, but henceforth September, geting down the season, fiishing production of the fresh water trouts are only on one of Yana and the connection in steam-pressure, rain falling qantity, and atmospheric temperature is plus on Yana, minus on a casting net and angling.
For, by cause of Yana is activetic to a casting net and angling are selfmoving.
We able to know element of atmospheric phenomena shall make influence over the fishing production as condition of the fisheries catching. (conclution)

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