Will Typhoon Cause Great Damage to Juvenile Hybrid Grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) under Indoor Flowing Seawater Aquaculture Model?
Will Typhoon Cause Great Damage to Juvenile Hybrid Grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) under Indoor Flowing Seawater Aquaculture Model?
Jing Hu1,2,3 and Zhenhua Ma1,2,3*
ABSTRACT
Typhoons can hit the aquaculture industry. In this study, the water quality during typhoon was simulated under indoor water flowing seawater aquaculture model (C: salinity 32.5%, ammonia nitrogen 0.01mg/L; T1: salinity 30.0%, ammonia nitrogen 0.04mg/L, T2: salinity 27.5%, ammonia nitrogen 0.10mg/L; T3: salinity 25.0%, ammonia nitrogen 0.18mg/L) to investigate the tissue damage of gills and head kidneys and the changes of serum indicators of hybrid grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) in 96 h. The results showed that the survival rate of each group was 100%, and no abnormal behavior was observed in juvenile fish. The damage performance in gill generally deepened over time. Lamellar fusion and curling of secondary lamellae also deepened from C group to T3 group. The proportion of interrenal tissue and hematopoietic tissue was moderate in all head kidney. Tissue vacuoles, ambiguous cell boundaries and necrotic cells deepened over time within 96h and also deepened from C group to T3 group. In all groups, triglyceride increased with time. In the treatment groups, the cholesterol was higher than that in C group at 6 h. The high-density lipoprotein cholesterol of C group remained stable at a higher level than the treatment groups. The low-density lipoprotein cholesterol of C group remained stable at a lower level than the treatment groups. The changes of serum ion concentration in hybrid grouper over time can be divided into three categories: change near the level of the C group (Na+, K+), roughly higher than the C group (Cl-, Fe3+, P5+) and roughly lower than the C group (Ca2+, Mg2+, Zn2+). The serum urea nitrogen showed an increasing trend, while serum creatinine and uric acid showed a decreasing trend. In conclusion, the simulated typhoon seawater can damage the gills and head kidney tissues of juvenile hybrid grouper, and obviously affect the serum indicators, but some indicators can be restored to normal by adaptation. From the perspective of this study, indoor flowing seawater system can be properly opened during typhoons, but attention should be paid to water quality monitoring and to observe whether juvenile hybrid grouper has abnormal behavior.
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