환경 스트레스에 대한 조피볼락(Sebastes schlegeli)의 생리학적 반응

Abstract

Production of Korean rockfish Sebastes schlegeli from aquaculture has been rapidly increased during the past decade and the fish has become the second most important mariculture fish in Korea. However, there are some problems of environmental factors in Korean rockfish aquaculture recently. In this regards, this study investigated the effects of environmental stressors: 1) high water temperature, 2) low salinity, 3) hypoxia, 4) ammonia toxicity, on physiological condition.

Stress responses of Korean rockfish to high water temperature Stress responses to high water temperature was examined via oxygen consumption, blood physiological parameter and endocrinological method. Oxygen consumption of Korean rockfish had significantly increased with rising water temperature. The levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) showed no difference until 30℃, but it had rapidly increased at 30℃. Moreover high water temperature affected to increase in plasma glucose and cortisol levels. However, all hematological parameters had significantly decreased after 5 days at 27℃. These results suggest that Korean rockfish recovered from high water temperature after 5 days at 27℃. Also, feeding and survival of Korean rockfish maintained the status quo after 5 days at 27℃.

Stress responses of Korean rockfish to low salinity Plasma Na+, Cl- and osmolality had continuously decreased in 5 psu. Increase in glucose and cortisol concentration has shown immediately transferred to 5 psu from seawater, and after 10 days. Korean rockfish prolactin (RRL) cDNA consists of 1522 bases, in which 213 amino acids are encoded including 25 signal peptides. In this experiment, expression of PRL mRNA in the pituitary gland of Korean rockfish had significantly increased during 5 psu acclimation. These results show that PRL may play hormonal regulation in osmoregulatory organs, thereby improving the hyper- osmoregulatory ability of Korean rockfish in 5 psu.

Stress responses of Korean rockfish to hypoxia The objective of this study was to evaluate the effects of acute hypoxia on the physiological stress response (plasma cortisol as the primary response, and plasma glucose, hematocrit, hemoglobin, sodium, chloride, osmolality, AST, ALT and total protein as the secondary responses) of Korean rockfish. The mortality in Korean rockfish started at 0.68 mg/L and 0.81 mg/L levels at 12℃ and 20℃, respectively. And the time required for the mortality in experimental fish was 280 and 140 minutes at 12℃ and 20℃, respectively. The mortality in 20℃ was higher than 12℃, and decreasing speed of dissolved oxygen in 20℃ was faster than 12℃. Levels of hematocrit, hemoglobin, AST, ALT, total protein, ion concentration, osmolality, glucose and cortisol had significantly increased with decreasing dissolved oxygen.

Stress responses of Korean rockfish to ammonia Mortality was not shown until 24 hours in 5 and 20 ppm. 100% of mortality in Korean rockfish was shown at 12, 6 and 3 hours in 50, 100 and 200 ppm, respectively. Levels of hematocrit had significantly increased in high concentration (over 50 ppm). Levels of glucose and cortisol had significantly increased in all the experiments. Club-shaped lamella and desquamation were observed in gill tissues exposed to ammonia.