산란 유도 호르몬 처리에 따른 붉바리 Epinephelus akaara의 난질 평가 인자 분석

Abstract

Control of spawning is essential for the sustainability of aquaculture production in captivity and egg quality management is an important for healthy seed production of fish. The red spotted grouper Epinephelus akaara, have high commercial value in Korea, Japan, China, and Southeast Asia. However, commercial production is still very limited due to problems of spawning induction and synchronization. The objective of this study is to improve the quality of spawned eggs through hormone treatment and the quality was evaluated by morphological characteristics, fatty acid composition and maternal gene expression [cathepsin B and D]. Red spotted grouper broodstocks were injected intramuscularly with human chorionic gonadotropin (hCG), prostaglandins (PGs; PGE2 and PGF2α), and luteinizing hormone-releasing hormone analog (LHRHa). Spawning occurred 36 to 40 hours after hormone treatment. The spawning rate was 47.8±3.95% at hCG treatment, 41.7±8.33% at PGF2α treatment and 37.5±12.50% at LHRHa treatment group. Fertilization rate was 81.4±14.30% at hCG treatment, 92.8% at PGF2α treatment and 99.1±0.46% at LHRHa treatment. The spawning rate was highest at hCG treatment group. The highest fertilization rate was observed at LHRHa treatment group. Egg and lipid droplet diameters were observed after 1, 2, 3, 6, 12, 24 and 36 hours of fertilization and the resorption rates of yolk in larvae were analyzed after 0, 2, 12 and 24 hours of hatching. In LHRHa treatment group, the volumetric ratio of lipid droplet/egg (L/E) was higher than that of hCG treatment group. The yolk volume in the LHRHa treatment group was higher than that of the hCG treatment group. The docosahexaenoic acid (DHA) in PGF2α treatment group was higher than that of LHRHa and hCG treatment groups. Cathepsin B expression of LHRHa treatment group was higher than hCG treatment group until 36 hours after fertilization. The results of this study indicate that LHRHa treatment is effective for egg quality improvement in E. akaara, although the spawning rate is lower than the hCG treatment group.