In aquaculture, salinity is an essential factor regulating fish growth. There is a report that fish can use this energy for growth if the salt concentration is lowered because the energy cost used for osmoregulation is high when the fish usually live in the salt concentration of the sea. Also, a study showed a significant difference in food intake when changed the salt concentration. The expression of ghrelin was also thought to be changed because the word indicating the difference in food intake means a change in appetite. In this study, ghrelin gene expression and growth were analyzed to investigate changes in food intake and growth according to salinity differences. In addition, by confirming the expression of LEAP2, an antagonist of ghrelin, the effectiveness of ghrelin’s appetite stimulation was indirectly confirmed, and growth hormone, acyl ghrelin, and glycogen were measured to measure growth hormone changes and growth according to additional food intake.
There was no significant difference in weight gain (%), specific growth rate (%), feed efficiency (%), and daily feed intake of the starry flounder. The ghrelin expression in the starry flounder decreased after feeding and showed a common tendency that the expression increased as the fasting time increased. In all experimental groups, the expression of LEAP2 in starry flounder exhibited an opposite trend to that of ghrelin, with expression decreasing as fasting time increased. In the 0 psu experimental group, a 7-fold increase in ghrelin expression showed an increase in the growth hormone concentration in the brain of the starry flounder. The concentration of acyl ghrelin in the starry flounder of all groups increased with a time difference with the expression of the ghrelin gene. According to this study’s results, ghrelin’s expression was amplified at 0 psu, leading to an elevation of growth hormone. These results provide basic physiological information for studying fish salinity and ghrelin.