|Abstract: ||本研究在於探討吳郭魚-浮萍魚菜共生的可行性而進行兩實驗:(一)以浮萍取代部分商用飼料對於水質及紅色吳郭魚成長之影響(二)不同魚隻大小對於紅色吳郭魚-浮萍魚菜共生系統水質及浮萍生長之影響。 (一) 本研究目的在於探討以浮萍取代一天飼料對魚隻成長及有無浮萍存在養殖系統對於水質之影響，實驗有三處理，A組為7天皆餵食飼料(桶中無培養浮萍)，B組為6天餵食飼料及1天餵食新鮮浮萍(桶中無培養浮萍)，C組為6天餵食飼料與1天餵食新鮮浮萍(桶中以箱網培養浮萍)。飼料使用35.83 % 粗蛋白質含量(CP)之商業飼料；新鮮浮萍(Landoltia punctata) 粗蛋白為35%(乾重)、水分則是92.5%，投餵量與所投餵飼料等蛋白量之新鮮浮萍。浮萍每週收穫一次(採集生產面積一半的量)。魚體初重為4.9±0.91 g，養殖12週。結果顯示三組之間在食物(飼料+浮萍)轉換率(Food conversion ratio , FCR2)有顯著差異，其分別為2.25、6.47、6.35，其餘在飼料轉換率(FCR1)、週比成長率(SGR)、增重率(WG%)等成長參數間皆無顯著差異。在水質方面，總氨氮、亞硝酸鹽等參數皆有顯著差異，濃度皆為A>B>C組，表明系統中有浮萍存在能有效降低水中營養物質含量，結果顯示以浮萍取代一天的商用飼料不會造成成長差異且能改善水質。 (二) 本研究目的在於探討紅色吳郭魚-浮萍之魚菜共生系統，魚的總初始放養生物量相同 (44.84±0.09 g)，但魚的大小與尾數不同 (分別為5.61±2.38 g，8尾及11.20 ±1.17 g，4尾) 時，對於魚與浮萍之生產及水質的影響。此魚菜共生系統置放細目箱網，將網內的浮萍與魚隔離，然後每週一次將箱網內培養出的浮萍(Landoltia punctata)，收穫一半，每週2天將之餵予吳郭魚，其他5天餵食飼料，1天不餵食，歷經8週，結果顯示結果顯示，小魚組在總末重、總增重量、增重率、週比成長率皆較大魚組高，在飼料轉換率、浮萍轉換率、食物轉換率及蛋白質效率則是小魚組優於大魚組。在水質方面，總氨氮、硝酸鹽等參數皆無顯著差異，顯示本實驗中不同大小的魚所產生的營養物質尚在浮萍吸收能力的範圍內。浮萍生產量則是在第5週後小魚組多於大魚組，根據結果，我們建議以小魚來進行生產會是最佳選擇。|
Abstract The aim of this study was to investigate the effect of feeding of commercial feeds and fresh duckweed on the growth of the fish, growth of the duckweed and its impact in water quality. The experiment is divided into two parts;(1) the duckweed to replace commercial feed, its effect on growth of Red tilapia and in water quality (2) different size of Red tilapia- duckweed fish symbiotic effect in duckweed growth and in water quality. For experiment 1, the purpose of the study was to evaluate the use of duckweed as a replacement of the commercial feed on the fish growth and its effect in water quality. The experiment has three treatments with 3 replicates. Group A for 7 days feeding with commercial feed (no duckweed cage culture), group B and C, both fed with 6 days commercial feed and 1-day fresh duckweed. The difference between the two was for group B no duckweed cage culture inside the tank while group C has. Feed and fresh duckweed (CP: 35.00%; moisture: 92.5%) were fed at 3% of the body weight of the fish. Treatments were fed with the same protein content of 35.83%. Duckweeds was collected once a week (1/2 of the production area). The initial weight of fish was 4.9 ± 0.91 g and cultured for 12 weeks. The results showed that, there were significant differences in food conversion rates between the three groups, which were 2.25, 6.47 and 6.35, respectively. No significant difference was found in total final weight (TFW), total weight gain (TWG), survival rate (SR), feed conversion rate (FCR) and protein efficiency ratio (PER). The results showed that a day of feeding fresh duckweed will not cause growth differences. In terms of water quality, significant differences were found in total ammonia nitrogen (TAN), nitrite (NO2-N), nitrate (NO3-N) and phosphate (PO4-3). It indicates that, the existence of duckweed in the system can effectively reduce the nutrients in the water. For experiment 2, the purpose was to evaluate the effect of different sizes of Red tilapia with the same biomass on the growth of duckweed and in water parameters. Treatments were consisted of two fish sizes: small (8 fish, average body weight: 5.61±2.38g) and medium-sized fish (4 fish, average body weight: 11.20 ±1.17g) with 3 replicates. The experiment was performed with 5 days feeding of commercial feed, 1-day feeding of fresh duckweed and 1-day without feeding and carried out for 8 weeks. The duckweed was collected once a week (1/2 area) and production was recorded. The results showed that, the small-sized fish group had the better growth performance in terms of TFW, TWG and SGR. Medium-sized fish group had the poor FCR and lowest PER. No difference was found in SR. For duckweed growth, small-sized fish had the highest duckweed production. No significant differences were also found among the water parameters, indicating that the nutrients produced by fish are still in the range of absorption capacity of duckweeds. In conclusion, the feeding of commercial feed with duckweeds will not affect the growth performance of the fish. For the duckweed production, small-sized fish was recommended and the best choice.