Hydrodynamics Characteristics of Slotted Saucer-Shaped Otter Boards

槽洞圓型網板之力學特性

林梭辰(Jiun-Chern Lin) ； 蘇偉成(Wei-Cheng Su) ； 周耀烋(Yau-Shou Chow)

《臺灣水產學會刊》 21卷1期 (1994/03) Pp. 1-10

https://doi.org/10.29822/JFST.199403.0001

摘要

爲瞭解魷類（或鎖管）在集魚燈下之時空分布狀況，將在基隆外海所採集到之鎖管(Loligo edulis)活體標本從事水槽測試，分析鎖管在水槽內對不同光度情況下之能譜週期與密度，以及空間分布特性。不論經由魚探機所積分之平均後方散亂強度，或者經由影像處理法所統計出之鎖管趨集密度，均以快速傅立葉轉換法(FFT)從事時序列分析，依隱週期所呈現之能譜週期與密度，再作圖析比較。其主要之結果如下：1.在白色燈光照射情況下，鎖管在表水層之游泳運動遠比在中水層時較爲活潑。於中水層，不論經由影像處理法或經由魚探機回訊信號處理法，所求出之鎖管洄游運動週期曲線，兩者趨勢極爲相似。2.在光度較強或較弱之情況，鎖管活動較頻繁位置係在燈源側方之表水層。當光電池讀數爲25 Lux時，鎖管活動較頻繁位置會出現在燈源直接投射之下方。該等特性顯示，鎖管被光誘集時除與好適照度有關外，其群棲行爲亦深受棲息環境相對照度之影響。即鎖管群聚密度與光之強弱，有密切之關係。3.相同基準照度之情況，因中水層以藍、綠光之穿透性較好，故鎖管在藍、綠光下之活動性亦較強。相對於紅色燈光，鎖管在紅色燈光下之活動性較不明顯，但其趨集位置最爲接近燈源及表水層。至於鎖管對於其它色光之趨集特性，則界於前述色光之間。據此，依集魚燈之用途特性而言，藍、綠色光適於作爲集魚燈，紅色燈光則適於作爲誘導燈。

關鍵字

槽洞網板 ； 展抗比 ； 壓力中心系數 ； 攻角

並列摘要

To understand the status of time and spatial distribution of the swordtip squid(Loligoedulis)under fluorescent lamp in water tank,the phototactic behavior of squid was observedunder different colors of light intensities.Data obtained by echo sounder and by imageprocessing were analyzed by Fast Fourier Transform.The results were summarized asfollows:1.Under white colored illumination,squid were more active on the surface thanin the middle of water tank.Based on the swimming activity obtained by image processingand echo signal processing,we found that both phototactic period curves are quite similarat the layer of middle water.2.When photocell reached 25 Lux,the most active area was the spot where thelight source was directed.When the baselevel illumination was stronger or weaker than25 Lux,the active area shifted to the lateral sides of the light.These special featuresindicated that the squid-gathering density was related to light intensity.3.Under the same illumination source,squid swam more actively in the areasilluminated by green and blue colored lights.However,squid swam less actively in thearea illuminated by red light,their gathering area being close to the light source andnear the surface of water tank.Based on these experiments of colors of light illumination,blue and green colors were suitable for fish gathering,the red light being suitable forseducing the fish school.

並列關鍵字

Slotted Otter Board ； Sheer-Drag Ratio ； Coefficient of Peressure Centre ； Angle of Attack