海水魚苗養殖上餌料適口性是最大的問題。本研究於實驗組(F)中添加並保持氮鹽在700 μg/l、磷鹽在100 μg/l,使浮游生物自然產生,以探討魚苗之初期餌料上之選擇及嗜食性,而控制組(N)則不添加營養鹽只投餵輪蟲 (Brachionus rotundiformis),並比較魚苗成長與活存率。結果顯示F組的赤鰭笛鯛 (Lutjanus erythropterus) 在孵化第三天(3 DPH, days post hatch),魚苗攝食俠盜蟲屬纖毛蟲 (Strobilidium sp.),N組則有攝食輪蟲;在21天後N組魚苗活存率為2.2 %,F組為0 %,有顯著差異(p<0.05)。在鞍帶石斑 (Epinephelus lanceolatus) 養殖實驗中,F組魚苗在孵化第3 – 5天攝食纖毛蟲 (3.59 ± 0.47 ind/fish),孵化8 – 24天攝食橈足類無節幼生,實驗結束時活存率為0.3 %;N組則在第八天全部死亡。點帶石斑魚(Epinephelus coioides)養殖實驗中,F組魚苗在開口後攝食渦鞭毛藻,緊接著攝食輪蟲,而N組魚苗開口後即直接攝食輪蟲,兩組的活存率以N組(8.1 ± 2.1)高於F組(2.3 ± 0.8 %)。赤鰭笛鯛、鞍帶石斑魚和點帶石斑魚的口徑上,赤鰭笛鯛與點帶石斑魚的開口口徑(221 ± 21 μm、181 ± 12 μm)大於鞍帶石斑魚開口(157 ± 5 μm),可直接攝食SS型輪蟲,鞍帶石斑則必須攝食更小的餌料生物 (eg. Strobilidiidae) 才能活存,而本實驗添加營養鹽方法可提供較小型的餌料生物,有助於海水魚苗初期攝食。
Marine fish larviculture has been unsuccessful partly due to the lack of suitable size of food. In this study, we maintained inorganic nitrogen at 700 μg/l and phosphorus at 100 μg/l to induce growth of different sizes of plankton in experimental group (F group), and no addition of nutrient in controlled group (N group) to compare the growth and survival rates. The results showed that the red snapper (Lutjanus erythropterus) were raised in F group, they started feeding on oligotrich ciliates (Strobilidium sulcatum) at 3 days post hatch (DPH), while those in the N group fed on rotifers (Brachionus rotundiformis) that we added. The survival rate were 2.2% in N group and 0 % in F group. When giant grouper (Epinephelus lanceolatus) was raised, in F group they fed on ciliates at 3 – 5 DPH (3.59 ± 0.47 ind/fish), and on copepods nauplii at 8 – 24 DPH, while those fed with rotifer in N group died off after 5 days, and the survival rate of F group were 0.3 % when the experiment ended. When orange-spotted grouper (Epinephelus coioides) was raised, they started feeding on dinoflagellates (Peridinium spp.) followed by rotifer when their mouth opened, while those in the N group fed on rotifer that we added. The survival rates were higher in N group (8.1± 2.1 %) than in F group (2.3 ± 0.8 %). Of the three species, the mouth size of red snapper and orange-spotted grouper were 221 ± 21 μm and 181 ± 12 μm, and can readily feed on rotifer, while giant grouper has small mouth size (157 ± 5 μm) that could only feed on small zooplankton (eg. Strobilidiidae). The results revealed that control of nutrient can provide preys of smaller sizes for larval fish that can enhance their survival in culture.