Energy Budget of Saline Milkfish Culture System in Taiwan

為探討魚羣單羣結構改變對超音波評估的影響程度，本實驗乃以日本鮆為對評估象魚種，利用光學聲學連動系統進行計測，由超音波囘訊評估之羣集密度及成對立體照片組解析之實際魚羣密度，探討不同單羣結構的評估誤差。由本實驗50組成對立體照片分析結果發現，日本鮆魚羣之單羣結構大致上可區分為規律性及塊狀分佈兩種，而這兩種截然不同的魚羣，超音波羣內積分法所評估的準確度也有相當大的差別，呈規律性的魚羣，超音波法評估的魚羣密度値與實際魚羣密度較為接近，其誤差在20％內，至於成塊狀結構的魚羣，則超音波的評估結果十分不穩定，且通常誤差率頗大，有高達一倍以上者，顯示魚羣單羣結構改變會對超音波的評估結果產生相當大的影響。並且魚羣密度愈低，其單羣結構愈容易產生變化，超音波囘訊積分法的評估誤差率愈高。因此，當利用超音波評估魚羣量時，對單羣因外在因素導致行為變化，使單羣結構改變時之囘訊應該予以剔除，以增加評估之準確度。

關鍵字

虱目魚；新陳代謝速率；培養底藻；能量預算

並列摘要

The present study investigated the effect of changes in the internal structure of schooling Engraulis japonica on the measurement efficiency of acousticmethods.A hydroacoustic system incorporated with an underwater camerasystem was used to compare the packing density estimated by acoustic systemswith the actual value obtained from the analysis of paired 3-dimension photograph sets.An analysis on 50 sets of paired 3-dimension photographsshowed that two kinds of structures were usually present in a single E.japonicaschool.For fish in regular spacing schools,an estimatd value of less than20% errors could be obtained.However,large errors were usually presnt inthe packing density of clump schools.Since fish schools with low densitychange their internal structures easily,errors in stock assessment also becamelarger for acoustic methods.Thus,when the internal structure of a schoolingfish was changed due to environmental factors,echo signals during structuralchanges should be deleted from integration to increase the accuracy of anacoustic method in abundance estimation.

並列關鍵字

Milkfish ； Metabolic Rate ； Benthic Algae ； Energy Budget

國際替代計量

Energy Budget of Saline Milkfish Culture System in Taiwan

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