Effects of different microalgal diets on intensive cultuvation of Cyclopoida copepod Apocyclops sp.

Abstract

Effects of different microalgal diets include Nannochloropsis oculata, Isochrysis sp. and Chaetoceros muelleri on mass culture of copepod Apocyclops sp. was conducted under five treatments (3 replicates) and the experiment lasted 25 days, treatment 1 (N. oculata), treatment 2 (N. oculata and Isochrysis sp., 1:1), treatment 3 (N. oculata : Ch. muelleri, 1:1), treatment 4 (Isochrysis sp. and C. muelleri, 1:1), treatment 5 (N. oculata, Isochrysis sp. and C. muelleri, 1:1:1). The results investigated that copepod fed mixing microalgal diets had better population growth than copepod fed N. oculata only. The highest density of copepod was detected in treatment 3 and 5 with 194.44 ± 101.84 and 194.44 ± 67.36 individuals/ L, respectively, these number were significantly higher than the density of copepod in treatment 1 with 67.67 ± 47.14 inds/ L (P<0.05) but no significantly different with the density of copepod in treatment 2 (105.56 ± 16.67 inds/ L) and treatment 4 (155.56 ± 67.36 inds/ L) (P>0.05).The highest population growth was in cultivation period from 15 to 20 days after that the copepod densities will be reduced. The results of fatty acid analysis showed that the highest DHA and EPA content was in treatment 3 with 32.15 and 16.34%, respectively. The lowest DHA content was in treatment 2 with 27.97% and the lowest EPA was in treatment 1 with 11.84%. The highest and lowest ratio of DHA/EPA was found in treatment 1 with 2.41 and treatment 2 with 1.93, respectively. The highest ratio of EPA/ARA was in treatment 4 with 2.21 and lowest in treatment 5 with 1.95. Based on the results of this study, N. oculata, and C. muelleri is recommended for intensive cultivation of Apocyclops sp.