In this study, experiments were conducted to investigate the effect of various feeds on the growth of elvers and juvenile eels (Anguilla bicolor pacifica). In the initial trial period, four types of feed, namely, paste feed, powder feed, frozen mosquito (Chironomus dorsalis) larvae, and powder feed mixed with frozen mosquito larvae, were fed to the elvers at a water temperature of 30 ± 0.5℃. After a rearing period of eight weeks, the elvers fed with the paste feed had the highest percentages of weight gain (927%) and feed efficiency (22.1%), with those percentages being significantly higher than those of the elvers fed with the other feeds. In addition, the group fed with frozen mosquito larvae had a significantly higher survival rate than the group fed with powder feed, although the larvae-fed group’s survival rate was not significantly different from those of the groups fed with paste feed and powder feed mixed with frozen mosquito larvae. The results showed that the paste feed can totally replace the frozen mosquito larvae during the initial period of elver rearing.
A three-month experiment to determine the growth of juvenile eels fed with floating pellets and powder feed was also conducted. The group fed with floating pellets had significantly higher percentages of weight gain and feed efficiency (266% and 87%) than the group fed with powder feed (204% and 52%). The group fed with floating pellets also had a higher condition factor with a relatively low moisture content compared to the group fed with powder feed. The ammonia and nitrite levels in the water were higher for the powder-fed group than for the group fed with floating pellets, with the nitrite level for the former group being significantly higher as of four hours after feeding. The results of the present study suggest that feed consisting of floating pellets may result in better feed efficiency and water quality.