틸라피아 양식에서 미세조류를 이용한 자가영양 바이오플락기술 개발

Abstract

Four experiments were conducted to develop the autotrophic biofloc technology (ABFT) system to reduce water replacement by using autotrophs (Chlorella sp. and Scenedesmus sp.) in Nile tilapia (Oreochromis niloticus).

In the first experiment to evaluate growth performance in fry fish averaging 0.02 ± 0.001 g (mean ± SD) were randomly distributed into two treatment (100 fish per 100 L tank, three tanks per treatment); control (50 % water exchange daily) and ABFT (0 % water exchange every 10 days, with inoculation of Chlorella ellipsoidea and Scenedesmus dimorphus). After 56 days of the feeding trial, there were no significant differences in growth, survival, whole body protein, other EAAs and NEAAs content among fish from ABFT and control, however whole body lipid content of fish from ABFT were significantly higher than those of fish from control, and arginine (one of EAA) and alanine (one of NEAA) of fish from ABFT were significantly lower than those of fish from control.

In the second experiment to evaluate water quality in growing fish averaging 15.1 ± 0.04 g (mean ± SD) were randomly distributed into three treatments (30 fish per 100 L tank, three tanks per treatment); negative control (0 % water exchange), control (50 % water exchange daily), and ABFT (0 % water exchange up to 9 days). After 9 days of the experimental period, survival rates of fish from negative control, control and ABFT groups were 100 %. The total ammonia nitrogen (TAN) concentrations of fish from ABFT were significantly lower than those of tanks from negative until 6th day, but higher than those of tanks from control for 9 days. Nitrate (NO3−) concentrations of fish from ABFT were significantly lower than those of tanks from negative for 9 days, but no significantly differences between ABFT and control until 6th day. Nitrite (NO2−) concentrations of fish from ABFT were significantly lower than those of tanks from negative and control for 9 days. (p < 0.05)

In the third experiment to evaluate growth performance in growing fish averaging 60.1 ± 0.25 g (mean ± SD) were randomly distributed into two treatments (218 fish per tank, 2 ton tank per treatment); control (50 % water exchange daily) and ABFT (90 % water exchange every 10 days = equivalence of 9 % water exchange daily, with inoculation of Chlorella vulgaris and Scenedesmus obliquus). After 56 days of the first feeding trial, whole body protein, lipid, essential amino acids (EAA) and the most of non-essential amino acids (NEAA) content of fish from ABFT were significantly higher than those of fish from control, however, there were no significant differences in growth and survival among fish from ABFT and control.

In the fourth experiment to evaluate survival and immune responses in growing fish averaging 85.9 ± 2.26 g (mean ± SD) were randomly distributed into three treatment groups (20 fish per 100 L tank, three tanks per treatment); a negative control (0 % water exchange), a control (50 % water exchange daily), and ABFT (0 % water exchange). After 9 days of the experimental period, GOT, GPT, SOD and Lysozyme activities of fish from ABFT were significantly improved better than those of fish from negative control and control groups. Survival rates of fish were 100 a, 93 a, and 12 b (%) from control, ABFT and negative control groups, respectively. Therefore, these results strongly indicated that the ABFT could be a new eco-friendly aquaculture system for Nile tilapia culture.