漁業生産活動を通じて得られる漁獲情報を基に来遊魚群の量的,質的な評価を行うことは常に求められている。使用する漁具の漁獲特性を予め十分明らかにしておくことが重要である。受賞対象となった一連の研究は刺網・貝桁網漁具の漁獲特性を漁獲の過程から捉えて,対象生物,漁具の物理的視点より水産工学的に研究を展開して,漁獲選択性,漁獲効率などに関して究明したものである。刺網では産業的に重要な北洋のサケ・マス刺網漁業を対象に取り上げた。魚の罹網機構について漁獲の過程から捉えて,魚の遊泳力,網目と魚体の力学的諸関係から新たな漁獲選択性曲線を求める方法を考案した。そして,数値計算を行って漁獲選択性に影響する要因,網地目合,網糸直径,網糸弾性,魚種,魚の肥満度,魚肉の弾性,魚の雌雄について検討した。また,漁獲効率,目合と網糸直径,調査用刺網の目合と網糸直径についても究明した。貝類は一般に成長は遅く,充分な資源管理を行って利用することが強く求められている。貝を捕獲するのには桁網が多く用いられている。貝桁網漁具の漁獲特性を予め充分明らかにしておくことが重要である。北海道海域における砂に潜って棲息している潜砂性の二枚貝を捕獲する桁網を対象に研究を進めた。桁網の爪部分および袋網部分の選択性について注目して,それぞれの部分から貝が抜ける時の姿勢を三次元的に捉えて,貝の大きさ,爪間隔,網目形状,大きさとの関係から,両者の部分から抜けない確率模型を構築し,桁網の漁獲選択性曲線を理論的に求めた。また,砂の中に潜っている貝が爪に接触し砂面に持ち上げられる時の力学的条件から,最適な爪形状について究明した。さらに同じ仕様の桁網を二台前後に連結して同時に曳網することによって桁網の効率を精度良く求める方法を提案した。これらに関する一連の研究については報告されているので,ここでは,研究慨要の要点を論述する。

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GPS has become an indispensable tool in fishery by fishing boat recently. A positioning accuracy (horizontal deviation: 2DRMS) has been 15.9m by SGPS and 4.5〜6m by DGPS in case of HDOP is 1.5 after cancellation of selective availability (SA). The positioning accuracy improved 10 times as compared with after GPS started. Although GPS is such a convenient tool, the main usages of fishery are safety navigation and search of fishing point. In this paper show that a possibility of the application to the monitoring of a movement of fishing gear and the management fishery by DGPS.

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漁船等に代表される19GT未満の小型船は,他の船舶と比較して,波高が1[m]以下の低い場合でも大角度動揺が生じる場合がある。このため波高の推定は小型船の耐航性能を考察する上で重要な問題である。本研究では動径基底関数ネットワークモデルを用いることにより,海域特性を学習させた入出力系を構築した吹送距離と風速に基づく推定法を提案し,従来の推定法との推定精度の比較を行った。ネットワークの学習に関しては,合計38組の計測データセットから10組のデータセットを抽出し,この10組のデータセットを用いて,入力を吹送距離と風速,出力を有義波高としてネットワークの構築を行った。推定においては,残り28組のデータセットに関して,この入出力系が当てはまり有義波高の推定が可能かを検証した。その結果,本研究での提案法がより精度の高い推定結果を示した。ただし,ネットワークの構築のための学習に用いた入力変数の変域以外の入力変数に対しては十分な予測ができない可能性があるため,今後更に観測データを増やし,より広い変域での入出力変数を用いてネットワークモデルの学習を行っていく必要がある。

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Along the Okhotsk Sea coast of Hokkaido, the scallop (Patinopecten yessoensis) seabed sowing cultivation has been successfully performed with the four-year cycle system of mariculture. The scallop aged four is caught by the pair of dredge nets of a 14GT size vessel. However, scallop dredging operation consists the cycles of the strenuous works, such as the dredge net hauling, emptying and sorting of the catch. In this report, the author explained the field investigation of the scallop dredge fishery conducted in Tokoro fisheries cooperative association. And a method for simulating the dredging operation was developed with consideration of the cumulative catch in the fishery ground. It showed that scallop catch efficiency decreases remarkably as the cumulative catch become close to the initial stock. The relationship between the scallop dredging operation characters and the cumulative catch could be evaluated from this calculation model.

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In order to construct the recycling system of fisheries tray, it is necessary to assess the cleaning effect. In this paper, a starch solution is used to make artificial fisheries tray that has homogeneous stain. According to the characteristic of starch and iodine, the cleaning effect can be measured with image processing by analyzing the relationship between the residue and total stain. Moreover, in order to confirm the evaluated accuracy of cleaning effect, a weighing method is used. And it is obvious that the result of the measurement with image processing is actually the same as those of weighing one. As a result, the evaluating method of stain elimination rate, with practicability, economics and high accuracy, is developed. The following results are obtained : 1) The accuracy of measurement with image processing is high. 2) The cleaning effect can be assessed in detail with image processing, and it is useful for controlling the cleaning condition. 3) Compared with a conventional method, the method with image processing is simpler and costs less time.

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Catamarans have wider deck area and larger transverse stability compared to monohull ships. For fishing vessels, since these features are great advantages, catamaran hull form is a promising. Most of problems in the design of the catamaran are related to the seakeeping performance. Therefore, it is necessary to examine the seakeeping performance by the numerical calculation in the design of fishing catamarans. In this report, the calculation methods based on a strip method and results of seakeeping performance of fishing catamaran are presented. In addition, the outline of a constructed fishing catamaran is also described and problems and future tasks are addressed.

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Based on the severe indication concerning the enforcement of the suitable evaluation, the reservation of the transparency, etc. to public works, the evaluation concerned mainly with the cost-benefit analysis is carried out in each public work in recent years. However, when it stands on a national viewpoint, it is important to explain synthetically the effect which the concerned public works brings, such as the benefit to the local economy and to the consumer. For this, reason the measurement point of the effect, fishing port improvement work brings, in a series of process from landing of a marine product to consumption was proposed and the quantitative grasp of the benefit by the improvement work of Kesennuma Fishing Port in Miyagi prefecture was tried.

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近年普及してきたデジタルビデオカメラ(DV)を用いて,オオクチバスの遊泳行動を簡易的に解析した。回流水槽内で強制的に遊泳させ,遊泳フォームをDVにより撮影した。オオクチバスは1.17±0.16 TL/sec(対全長比速度)以上で一定の尾鰭振動数と振幅で遊泳したが, 1.88±0.24 TL/sec 以上ではBurst-and-coast遊泳を示し, 3.29±0.92 TL/sec 以上では遊泳の持続が不可能であった。大型アクリル水槽内でキンギョを餌として与え,一連の捕食行動を正面と側面に設置した2台のDVで撮影した。最高遊泳速度,加速度はそれぞれ, 5.8 TL/sec, 8.5m/sec^2に達した。低い耐久力と高い瞬発力に特徴付けられる遊泳は,待ち伏せ型であるオオクチバスの捕食戦略を反映している。

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琵琶湖固有の定置網であるエリ周辺で,コード化超音波発信機と設置型受信機を用いてオオクチバスを追跡した。オオクチバス4尾(TL : 34.0〜37.0cm)の腹腔内に受信機(Coded V8SCL, VEMCO製)を埋め込み,エリの中心に放流した。エリの垣網に設置型受信機(VR2. VEMCO製)3台を250mと敢えて間隔を狭めて仕置し,詳細な移動を把握した。50日以上追跡した2尾は, 10℃以下の低水温にも関わらず,昼間にエリから遠ざかり,夜間にエリに近づく日周移動を示した。同時にエリ周辺に設置した流向流速計の記録から,5m/sec以上の南西流が卓越した後,個体はエリから遠ざかったことが分かった。受動型漁具である定置網の漁獲には対象魚の移動と周辺の流動環境が密接に関わっていると考えられる。

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Immature Pacific bluefin tuna, Thunnus orientalis, marked with archival tags, were released off Tsushima Island in the East China Sea. Time-series data on swimming depth, and ambient and peritoneal cavity temperatures were recorded every 128 s to investigate their thermoconservation mechanisms under low ambient temperature. In summer the difference between peritoneal and ambient temperatures became appreciably large, as ambient temperature decreased due to repeated dives to depths below the thermocline for short periods, perhaps for feeding. This suggests that peritoneal cavity temperature is maintained during dives. A heat budget model revealed that thermal inertia, or internal heat production in the daytime, was important for thermoconservation during dives to depths below the thermocline. As bluefin could only maintain body temperature for a short period, they had to avoid rapid temperature change at the thermocline through behavioral thermoregulation. This is quite different from the situation for bigeye tuna, as reported elsewhere. In addition, it was also revealed that vertical diving activity could be related to physical conditions such as light intensity. The bluefin made few dives on days when solar radiation was comparatively low, implying that low visibility may prevent dives to depths below the thermocline.

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For quantitative assessments of the effect of artificial reefs to accumulate fish school. we developed a low cost fish school monitoring system (FISCHOM). which enables visual and acoustical observation of fish resources for more than several days. In this paper, we report the profile of prototype FISCHOM and the outcome of trial survey. FISHCOM is consisted of two sensors (a stereo camera with two strobe lights and an echo sounder), a programmable timer, a battery, and a pressure resistant housing with a visually and acoustically transparent window for the sensors. All components except for the housing were selected from inexpensive articles on the market. A digital camera captured two visual images apart 50 cm away each other, which was combined together by a stereo photogrammetric mirror. The stereo images enable us to measure the three-dimensional information of fish school (e.g. fish length tilt angle, distribution). Two sensors acquire a set of data every optional interval (from several seconds to hours) controlled by the programmable timer. A trial survey was carried out at a high-rise artificial reef located off Atsumi, Yamagata prefecture on May 2003. FISCHOM succeeded a 5 days monitoring with an hour interval of data acquisition. We obtained a time series data of individual number of fish, fish length and distance from FISHCOM by the stereo camera, and fish school distribution by the echo sounder. We have demonstrated that the FISCHOM is appropriate to obtain quantitative and continuous data of fish school than other observation methods, which commonly used for the artificial reef assessment, such as observation by SCUBA diver, angling sampling and fish echo sounder operated on a boat.

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The Heart rate and the activities of a red sea bream were measured simultaneously in a saltwater pond. The heart rate was measured using an ultrasonic transmitter. The activities including 2 axes acceleration, swimming speed and depth were measured using a data logger. After sunrise, the fish became active and the heart rate showed 8% increase. Applying the relationship between metabolic rate and ambient water temperature obtained in laboratory trials, the oxygen consumption and the out put volume were estimated to have 18 and 10% increase, respectively. The estimated metabolic rate by applying the equation of motion was an overestimate considering the energy efficiency. While the fish dashed and cruised with tail beat frequencies at 3.8 and 1.8 Hz, respectively, the heart rate was stable.

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Waves are known to be one of the factors to influence the distribution of the seagrass and seaweed beds. The wind environment, which is one of the effective conditional factors of wave formation were investigated over a ten year period (1992-2001) in Hiroshima Bay to clarify the characteristics of the distribution in Hiroshima Bay to clarify the distribution of seagrass and seaweed beds. The index of the wind environment was analyzed based on the frequency of wind direction, velocity of the wind, and force of the wind. In this research, the wind force was estimated by accumulating the value of the third power of the velocity of the wind, and the effect of wind conditions were compared between the northern coasts and the southern ones. The results showed that the wind parameters, frequency of the wind direction, velocity of the wind, and force of the wind were larger in the wind direction of north or north-northeast than other wind directions. Moreover, the force of the northern winds (from NNE to NNAV) was higher by about five times than that of the southern winds (from SSE to SSW). These results suggest that coasts facing the north were more susceptible to force of the wind than coasts facing south.

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