不同食物對橈足類短角異劍水蚤族群成長及脂肪酸組成之影響

Abstract

DHA和EPA為魚類成長發育及維持正常生理代謝所必須的重要脂肪酸，而橈足類含高量的DHA和EPA，因此橈足類成為水產種苗重要的餌料生物。傳統的橈足類戶外粗放混養方式，容易讓病毒等病原體隨著橈足類由戶外攜入種苗池，為了培育優質且無特定病原之橈足類，可以特定藻類食物，生產出高密度的橈足類，然而藻類的培養，除了需要較多的人力及空間，亦容易受到敵害生物之競爭及氣侯影響。緣此，本實驗嘗試建立一個純淨的培育方式及更換其他食物配方供給橈足類生長所需，以達到餌料生產之目的，同時亦探討以藻類及其他配方為食物的橈足類體內所含的脂肪酸組成差異。短角異劍水蚤 (Apocyclops royi) 是在養殖池中常見的橈足類，本實驗以周氏扁藻（Tetraselmis chui）及其他人工食物配方來培養短角異劍水蚤13天，並觀察族群變化。於第14天收集蟲體分析脂肪酸組成，發現餵食周氏扁藻的蟲體，密度為每公升23,100隻，DHA和EPA分別佔總脂肪酸的4.44%與2.15%。餵食蝦片的蟲體，密度為每公升3,750隻，DHA和EPA分別佔總脂肪酸的4.00 %與2.36%。餵食人工配方的蟲體，密度為每公升5,475隻，DHA和EPA分別佔總脂肪酸的15.08%與1.86%。餵食人工配方二的蟲體，密度為每公升6,700隻，DHA和EPA分別佔總脂肪酸7.09%與3.96%。以產量而言，藻類仍然是生產短角異劍水蚤之最佳食物來源，但以便利性而言，人工配方餵食不但可省去藻類培養的所需的成本及時間，亦可去除天候因素及外來生物的影響，以維持短角異劍水蚤的一定生產量。另一方面，由脂肪酸分析結果得知，餵食含高量α-linolenic acid的配方一之短角異劍水蚤體內 DHA比其他實驗組高出許多，推論短角異劍水蚤可自行將α-linolenic acid轉換成DHA。

DHA and EPA are important fatty acids that essential for fish development and physiological function maintenance. The rich content of DHA and EPA in Copepoda enables it become an important living food of fish fry in aquaculture. Traditional outdoor and mixed culture of copepoda brings virus pathogens into fish fry culture pond easily. The high quality and high density culture of copepoda with no specific pathogens can be achieved by providing specific algae as food. However, the culture of algae needs intensive labor and large space, and is easily influenced by the competition of harmful biological organisms and climate. In order to cope with the problem, we tried to establish a pure culture system and design the food formula for copepoda to produce the living food for fish fry. Besides, we also compare the fatty acids composition difference between copepoda that fed with algae and other formula food. Apocyclops royi is a common copepoda found in aquaculture pond, so we use Tetraselmis chui and other formula food to culture Apocyclops royi for 13 days and observe its population changes. On the 14th day, the copepoda were collected and the fatty acids composition were analyzed. We found that the density of copepoda that fed with Tetraselmis chui is 23,100 per liter, and the DHA and EPA composition is 4.44% and 2.15% in total fatty acids, respectively. The density of copepoda that fed with shrimp chips is 3,750 per liter, and the DHA and EPA composition is 4.00% and 2.36% in total fatty acids, respectively. The density of copepoda that fed with formula food I is 5,475 per liter, and the DHA and EPA composition is 15.08% and 1.86% in total fatty acids, respectively. The density of copepoda that fed with formula food II is 6,700 per liter, and the DHA and EPA composition is 7.09% and 3.96% in total fatty acids, respectively. As far as production volume is concerned, algae are still the best food to produce Apocyclops royi. However, from the convenience point of view, formula food not only can save the cost and time of algae culture, but also can avoid the influence from climate and other pathogen contamination, and maintain a stable production. Besides, from the analysis results of fatty acid composition, copepoda fed with formula food I that contain highly α-linolenic acid has particular high DHA production in copepoda, which may imply that Apocyclops royi can turn α-linolenic acid into DHA.