A Study On The Digestive Enzyme Activities Of Four Fishes In Ponds With Grass Carp (Ctenopharyngodon Idellus) As The Main Stocking Specie

Grass carp is an important conventional freshwater fish cultured in our country. Our test was conducted in ponds with grass carp as the main stocking specie. The activity of pepsin, trypsin, lipase and amylase in alimentary organs for grass carp (Ctenopharyngodon idellus), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis) and paddlefish (Polyodon spathula) were be determined in our experiment, and the four kinds of enzyme activities in different parts of alimentary organs changing with breeding time were be explored. We also calculated the correlation coefficient between digestive enzyme activities and length, weight, some water quality indexes. The results were as follows:1. The intestinal of grass carp had the higher activity of pepsin, trypsin and lipase than liver, but the activity of amylase in liver was between hindgut and foregut. The activity of pepsin, trypsin and amylase in intestinal for silver carp is higher than liver, and the activity of lipase was oppositely. The intestinal of bighead carp had the higher activity of pepsin than liver, and the activity of trypsin was oppositely. The highest activity of pepsin for paddlefish was found in the oesophagus, followed in order by the liver, stomach and pyloric caeca, the lowest was in the intestine tract. The duodenum had the highest activity of trypsin and lipase activity, followed in sequence by liver, pyloric caeca, stomach, and the oesophagus was at a medium level. The highest activity of amylase was found in the duodenum too, followed in order by the oesophagus, stomach, liver, and the lowest was in the pyloric caeca. Silver carp had the highest intestinal pepsin activity in the four fishes, and paddlefish had the lowest. The intestinal pepsin activity between grass carp and bighead carp had no significant difference. The highest activity of pepsin in liver was found in paddlefish, followed in order by bighead carp and grass carp, the lowest was in silver carp. The grass carp had the highest activity of trypsin in intestinal, followed in sequence by silver carp, bighead carp and paddlefish. The highest activity of trypsin in liver was found in grass carp, followed in order by bighead carp, paddlefish and silver carp. Paddlefish had the highest intestinal lipase activity in the four fishes, and followed in order by bighead carp, grass carp and silver carp. The highest activity of lipase in liver was found in grass carp, followed in order by bighead carp and silver carp, the lowest was in paddlefish. The activity of amylase in intestinal had little difference in the four fishes. The highest activity of pepsin in liver was found in grass carp, followed in order by silver carp and paddlefish, the lowest was in bighead carp.2. On the culturing period from June to October, the activity of pepsin for grass carp first rose then dropped, and the trypsin was oppositely. The lipase had the same variation with trypsin. The activity of amylase increased gradually with the addition of breeding time. The activity of pepsin for silver carp first dropped then rose in the whole culturing period, and the trypsin was oppositely. The activity of lipase for silver carp is high in early cultured time and then dropped in July, but the activity of lipase for silver carp increased obviously and then gradually reduced. The changing rule of amylase activity for silver carp was opposite to lipase activity. The activity of pepsin and trypsin for bighead carp had same changing rule, which first rose in July then dropped in August and increased in followed time. The activity of lipase increased gradually with the addition of breeding time and the activity of amylase first rose then dropped. The activity of pepsin for paddlefish first dropped then rose, and the lowest value appeared in August. The activity of trypsin increased gradually with the addition of culturing period. Lipase and amylase activity increased first and then declined, and the highest value appeared in September. 3. Our study found that length and weight had significant positive correlation with alimentary organs trypsin, lipase and amylase activities for grass carp. And this positive correlation also existed in gastrointestinal and liver trypsin for paddlefish, intestinal trypsin, lipase and amylase for bighead carp. Water temperature had significant positive correlation with alimentary organs pepsin, intestinal trypsin and alimentary organs lipase for grass carp. It also had significant negative correlation with hepatopancreas amylase for silver carp. The correlation between water temperature and digestive enzymes activities for bighead carp and paddlefish was not significant. Hardness and alkalinity had positive correlation with pepsin activity of the four fishes except liver pepsin activity for silver carp. But hardness and alkalinity had negative correlation with trypsin, lipase and amylase activities. Chemical oxygen consumption had significant negative correlation with lipase and amylase activities for paddlefish. Total nitrogen and total phosphorus had positive correlation with most digestive enzymes activities for the four fishes.The results of clustering analysis showed that silver carp and bighead carp had the most similar enzymes activities. And paddlefish had more similar enzyme activity to these two fishes than grass carp.