Abstract: The activities of digestive enzymes in intestine and hepatopancreas and muscular composition of amino acids were moni- tored in redfin culter (Cultrichthys erythropterus Culter erythropteru///) weighing 107.82g collected in January, May, July and September, and the daily changes in muscular composition of amino acids were studied in summer. The results showed that there were significantly higher activities of digestive enzyme in summer and autumn than those in spring and winter, the activity ofprotease higher than amylase in the same season (P〈0.05). The maximum activities ofprotease, amylase and lipase were observed from 19:00 to 21:00, at 19:00 and from 16:00 to 19:00, and the minimum activities were found at 7:00, 7:00 and 21:00. The muscular composition of amino acids was shown to be comprised of 18 kinds of amino acid, glutamic acid being the most abundant and cysine the least. The contents of five essential amino acid (valine, methionine, isoleucine, phenylanine and lysine) were significantly lower in winter than in other seasons (P〈0.05), without seasonal changes in the non-essential amino acids. Both total amino acid and total essential amino acids were found to be the climax in spring and summer and to fall into zenith in autumn and winter, the minimal contents of delicious amino acids in autumn. The findings indicates that wild redfin culter digestive physiology has season and day revolution, and amino content changes in different seasons imply that the metabolism in winter relies on the essential amino acid in the muscle.

Key words: different season, digestive enzyme, amino acid, Cultrichthys erythropterus