The Study Of Larval Development And Effect Of Stocking Density On Juvenile Individual's Growth, Feeding, Et Al In The Red Swamp Crayfish Procambarus Clarkii

Recent years,Procambarus clarkii culturing has development dramatically in the middle and lower reaches of Yangtze River region,for its gigantic economical benefit.Shrimp cultivation is of importance in aquaculture,concerned with effect and interest.Both the larval development and the effect of stocking density on juvenile individual's growth,feeding,et al in the red swamp crayfish Procambarus clarkii were studied systematically in this article.The main results were as follows:1.The body weight and length were measured,0.017g,1.031cm in forth instar while 0.005g,0.0482cm in first instar.The relative formulary of larval weight and length was W=0.0162L^1.5636,R²=0.9863.It was of a great variety of habitats during larval development.2.The experimental results indicated that activities of five digestive enzymes showed two different variation patterns during larval development of Procambarus clarkii.The activities of pepsin and tryptase were relatively high in both second instar and forth instar,and reached the greatest value in the forth instar,4.492 U/mgprot and 2.587 U/mgprot,respectively.The activities of amylase,cellulase and lipase increased significantly and then decreased,reached the greatest value in the third instar, 2.749U/mgprot,2.802U/mgprot,0.307 U/mgprot,respectively.But it was not significantly different between the third instar and forth instar.The activities of ACP,AKP and LSZ all increased from first instar to third instar,then decreased.But they were high in forth instar.3.Biochemical compositions,including water,crude protein,crude lipid,carbohydrate and amino acid,were determined.The content of water increased gradually, and was lowest in first instar,only 73.706%of the wet weight.The content of crude protein decreased from first instar to third instar which was 51.318%of the dry weight,then increased in forth instar.The content of crude lipid decreased continuously and significantly from second instar to third instar,actually from 31.179%of the dry weight to 24.390%.The content of carbohydrate was not significantly different during larval development,being 15.120%of the dry weight in first instar, most of all the larvaes.The content of amino acid had the same trend as crude protein. Among all the amino acids determined,content of Glu was the highest,the highest essential amino acid(EAA) content was Lys.There was little difference between the ratios of content of single EAA to total EAA during different stages of larval development of Procambarus clarkii.4.A 30-day rearing experiment was conducted in this study.The initial average weight of juvenile Procambarus clarkii was(0.015±0.004) g and the initial rearing density was 50,100,300,600,900 individuals/m²,respectively.The results showed that the growth of juvenile Procambarus clarkii was different significantly.With the rearing density increasing,the specific growth rate(SGR),daily weight gain(DWG), livability and exuviating rate decreased significantly,while SV increased.The average food consumption of every individual and feeding rate decreased.The food conversion ratio(FCR) was the same.The specific growth rate of protein and lipid and RL decreased significantly while Rp increased.5.The activity of ACP decreased in hepatopancreas in juvenile Procambarus clarkii,but decreased and then increased in muscle with the accretion of stocking densities.The activity of AKP decreased and then increased in hepatopancreas,while decreased in muscle.The activity of LSZ decreased both in hepatopancreas and muscle.The content of GLU,total protein,BUN varied greatly at five stocking densities.The activity of GPT was not significantly different in both hepatopancreas and muscle.The activityof AST increased in hepatopancreas;first decreased then increased in muscle.The activity of LDH increased then decreased in muscle,really low in hepatopancreas.