北海道日本海南西部の磯焼け地帯に位置する寿都町では,ウニの除去によりフシスジモク群落を造成して いる。そこに人工種苗のエゾパフンウニの放流を行なうと,群落の密度が徐々に低下する問題を抱えている 室内水槽でフシスジモクがエゾパフンウニから受ける部位別の被食圧を観察したところ,側枝と幼体は主枝 と下葉に比べて被食圧が高かった。寿都町におけるフシスジモクの生殖器床の出現時期を調査したところ, 7- 8月に出現した。またウニが分布する場所と除去した場所でフシスジモク幼体の出現状況を比較したと ころ,ウニを除去した場所だけで11月に幼体が出現した。これらのことからエゾパフンウニ人工種苗をフシ スジモク群落に放流した後,群落の本数密度が徐々に低下するのは,幼体が優先的に摂餌されて世代更新が 絶たれるためと仮定した。そこで密度が低下している群落において,幼体を保護して加入を促すために,生 殖器床が出現し始める7月にウニを漁獲した。その結果,漁獲後にフシスジモクの密度は回復した。よって フシスジモク群落にエゾパフンウニを放流して群落の密度が低下しても,数年に一回フシスジモクの繁殖時 期前に漁獲を行なうことで,群落は漁場として長期的に保全できるものと考えた。

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Environmental variables (light irradiance, temperature, salinity, turbidity, and chlorophyll a) in relation to macroalgal distribution were analyzed bimonthly from April 2001 to February 2002 in Hiroshima Bay. Three dominant species of brown algae, Sargasstm horneri, S. macrocarpum, and Ecklonia kurome grow at each different depth 0-1m, 1-3m, 3-9m, respectively. The environmental gradient from the inner to the outer part of Hiroshima Bay in the vicinity of the seaweed beds as well as along the center of the bay was surveyed. The suspended matter that originates as effluent from the Ohta River is suggested to lead to a decrease in the light attenuation. The quantities and the properties of suspended matter changed seasonally and varied between each seaweed bed. The attenuation coefficient is suggested to be influenced by the suspended matter concentration and the effects were much larger in the imer part of the bay than in the central and outer parts. The three dominant brown algae were distributed along the environmental gradient in Hiroshima Bay. The two sample Hest of environmental variables of temperature and salinity showed significant differences among the species, except for light irradiance. This means that light conditions might not restrict the distributions of these algae. This study concludes that other environmental variables might be important to detemine their distribution, even though macroalgae can acclimate to environmental changes.

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On the basis of observation data of water temperature and salinity at Uranouchi Bay during the convection period, the heat flux of sea surface cooling, the potential energy given to the water column by the heat flux, and the dissipation energy are estimated. The diameter and the circumference speed of the maximum convection eddy caused by surface cooling are also evaluated. These results are described as follows : ① The heat flux through sea surface is 130(Jm^-2s^-1) in December. It's almost the same as the estimation about Mikawa Bay by other methods. ② The potential energy per unit time (de_Q/dt) given to the water column by the heat flux is (4-17) × 10^-5(Jm^-3s^-1). More than half of de_Q/dt tums to the potential energy of water column, and the remainder turns to dissipation energy (thermal energy) and disappears. ③ The diameter of the maximum convection eddy caused by surface cooling is about 0.4 (m). The circumference speed of the eddy is about 0.001 (ms^-1).

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自由に遊泳する魚類の心拍数を連続的に測定する超音波発信機(ピシガー)を開発し,生簀内におけるマ ダイ成魚(尾叉長43.3cm,体重1.3kg)の心拍数変化を放流後41時間にわたってモニターした。放流直後, マダイの心拍数は80bpm (beats min^-1)以上の高い値を示したが,放流後21時間経過すると50-60bpmの 間で安定した。この値は,室内実験により求めた安静時の心拍数と同等であった。高い心拍数を示した放流 後21時間は,発信機や電極の装着,麻酔の影響からの回復期間であったと考えられる。

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The bottom sediment, benthic community, fish and larvae of commercial shellfish species were investigated at an artificial tidal flat in Mikawa Bay, Japan. Differences between low and high tidal flat areas were investigated. The central area of the development was comprised of fine sand, whereas fine sand and coarse sand were present in the original bottom of the tidal flat. Organic matter content was high in the waterway and the marginal area of the development. The water purification rate, in terms of macrobenthic biomass, was high in the central and marginal areas of the development. In contrast, biodiversity in terms of macrobenthos species abundance was low in the central area of the development. Thus the distributions in the water purification rate and biodiversity were different. Mactra chinensis, Mactra veneriformis, and Ruditapes philippinarum dominated the commercial bivalve species at different heights of the tidal flat. Platichthys bicoloratus dominated the fish larvae of commercial species, and distribution across defferent depths varied according to body length. The marginal area of the development was important for settling larvae. As distributions of dominant species and functions of the tidal flat are different, we suggest that it is important to ensure a range of consecutive depths when creating an artificial tidal flat.

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Daily catch data of coastal squid jigging boats, their light source output for fishing lamps and monthly mean wholesale prices of squid were collected from five fishing ports (Hakodate, Sado Island, Noto, Sakaiminato, and Tsushima) in Japan, for a purpose of evaluating optimum light source output, which created a maximum economic yield. The daily income were estimated from the relationship between daily catch data and monthly mean wholesale prices of squid. Then, the optimum light source output was calculated from the relationship between daily income and daily lighting expenses by each fishing management conditions. The results show that daily income and daily lighting expenses were significantly increased as light source output for fishing lamps were increased. The lower light source output which obtained by each fishing management conditions was advantageous when lighting cost become more expensive or wholesale price become cheaper then ever.

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This paper proposes the advanced rudder roll stabilization controI system with hybrid fin controI system based on multivariate auto-regressive model. To confirm the effectiveness of Fin and Rudder Multivariate Hybrid System, full scale experiments were conducted by using prototype hybrid control. Research and training vessel 'UMITAKA-MARU' of Tokyo University of Fisheries was used for experiment. The full scale experiments included measurement of roll angle, roll rate, heading, rudder angle and fin angle. The rudder roll stabilization system, fin stabilization system and hybrid stabilization.system were carried out for the experiments to compare the effectiveness of each system. Statistical analysis was used for the time series data obtained from experiments and the results show that the hybrid controI system with fin and rudder has good performance for reducing rolling motion and keeping course.

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2001年台風第15号,および2002年台風第21号が東京湾を通過する際に実海面で得られた資料を基に,波高 の短期統計量等について解析を行った。資料は,東京水産大学練習船海鷹丸ならびに神鷹丸に設置されてい る,マイクロ波式波高計により計測されたものである。 解析の結果,一般船舶や漁船の安全運航に対して,有義波高や最大波高を推定する従来の方法が,台風通 過時においても有用であることが確認された。一方,台風通過時の海面においてもP-M型スペクトルで一 様に近似して表現することが難しいことが確認された。

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資源管理のための魚礁や数m間隔で設置される漁具の位置を高精度で求めたいときには,キネマティック GPS (KGPS)の使用が考えられる。このKGPSには正確な位置が分かっている基準局が必要である。しかし, 緯度経度で表される位置ではなく,顕著な物標などの地理的な基準点(基準局)からの基線ベクトルのみが 必要な場合は必ずしも基準局の正確な位置は必要でない。そこで, KGPSの基準局位置に20mの誤差を与え, 利用者局の水平基線ベクトル誤差を実測により解析した。 その結果,利用者局の水平基線ベクトル誤差は,基準局位置の誤差量,誤差方向及び基線長によって顕著 な傾向を示した。また,利用者局の水平基線誤差量を表すことができる実験式を得たが,その誤差量は小さ く,上述の利用形態では無視することができる精度であった。.したがって,このような場合,基準局の位置 は単独測位のGPSやDGPSで簡単に求めても良いということが分かった。

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前報および前々報に続いて,海中に設置した電極に微弱電流を流すことにより,海洋生物の付着を防止す る試みを行った。水産大学校桟橋下と近くの海面に測定板を沈め,測定板への生物付着状況を調べた。電流 を加えた桟橋部を試験区とし,電流を加えない海面部を対照区とした。 1999年6月4日から9月6日までの 3ヶ月間(第1期)と,同年10月7日から翌年1月6日までの3ヶ月間(第2期)に分けて実験を行った。 第1期の電源には太陽電池と充電式電池を用い, 1998年度と同じ約5 Vの電圧,約70mAの電流を常時加え た。第2期では,充電式電池を用いないで,太陽用電池モジュールの起電力(最大約10V)を直接印加した。 両期とも,電極にはチタン細線を用いた。 第1期の実験結果, 5 Vの電圧がフジツボ付着防止効果を有することが周年的に確認できた。第2期の実 験では, 8.Ⅴ以上の電圧が印加されたのは, 1日平均5.3時間と推測された。その結果,海洋生物の付着防止 効果は確認されなかった。

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In order to protect the snow crab population a crab sanctuary was established. An Untethered Remotely operated Vehicle was used to gauge crab population numbers in the protected area and an unprotected area (reference point) between the years 1996-1999. UROV results conclude higher crab densities in the protected area each year of the test. Protection efforts were effective.

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