Four Kinds Of Fish In Saline-alkali Lake Pond Ecological Breeding Mode In Southern Xinjiang

Based on the ecological aquaculture model of lakes and ponds in saline-alkali waters of southern Xinjiang,this paper takes Cyprinus carpio,Carassius auratus,Ctenopharyngodon idellus and Triplophysa yarkandensis)as the research objects.To evaluate the growth traits and muscle nutritional quality of freshwater fish（Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus）and indigenous fish（Triplophysa yarkandensis）under the lake ecological aquaculture model in southern Xinjiang.The main results are as follows:1 Changes of physical and chemical indexes in aquaculture watersThe concentration of salinity,alkalinity,Na⁺,K⁺,Ca²⁺,Mg²⁺,Cu²⁺,SO₄^2-,CO₃^2-and HCO₃^-in Swan Lake,a demonstration site of lake ecological aquaculture model in southern Xinjiang,decreased significantly in July（P<0.05）.The salinity,p H,Na⁺,K⁺and CO₃^2-in August were 8.73,8.30,3225.53mg/L,67.46 g/L and 14.39 mg/L,respectively,which were significantly higher than those in July（P<0.05）.Ammonia nitrogen and nitrite increased to 0.24 mg/L and 0.12 mmol/L respectively in August,which were significantly higher than those in other months（P<0.05）.The salinity,alkalinity and ion concentration in Swan Lake decreased significantly in July（P<0.05）,and the water quality conditions were better than those in other months.In August,the concentration of ammonia nitrogen and nitrite increased significantly（P<0.05）,and the water quality was poor.2 Growth traits of major freshwater fishesThe SGR,RGR and WGR of Cyprinus carpio cultured in saline-alkali water were 0.53%/d,0.82%/d and 123.17%,respectively,which were significantly higher than those of Carassius auratus and Ctenopharyngodon idellus（P<0.05）.From April to September,the SGR,AGR,RGR and WGR of the three major freshwater fish species showed fluctuating changes,with an upward trend from April to July,a significant decrease from July to August,and an increase from August to September.The length-weight relationships of Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus were W_{Cyprinus carpio}=7.2790×10^-4L^2.4175（R²=0.9294）,W_{Carassius auratus}=5.7011×10^-4L^2.4290（R²=0.8962）and W_{Ctenopharyngodon idellus}=3.5135×10^-5L^2.8957（R²=0.9078）.The growth performance of Cyprinus carpio is better than Carassius auratu and Ctenopharyngodon idellus.Cyprinus carpio and Carassius auratus showed allometric growth,Ctenopharyngodon idellus showed uniform growth;the growth rate of the three major freshwater fishes was the fastest from June to July,and the growth rate decreased significantly in August（P<0.05）.The SGR and WGR of Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus cultured in saline-alkali water were lower than those cultured in freshwater.3 Analysis of muscle nutritional quality of major freshwater fishThe contents of moisture,crude protein,crude fat and crude ash in the muscle of Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus cultured in saline-alkali water did not change significantly from April to September（P>0.05）;The content of crude white matter in Cyprinus carpio muscle ranged from 22.35%to 22.54%,which was significantly higher than that in Carassius auratus and Ctenopharyngodon idellus（P<0.05）;The water content in the muscles of Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus under saline-alkali water culture was lower than that under freshwater culture,and the crude protein content was higher than that under freshwater culture.A total of17 amino acids were detected in the muscles of three major freshwater fishes,including 7 essential amino acids（EAA）,10 non-essential amino acids（NEAA）and 2 delicious amino acids（DAA）.The contents of total amino acids（TAA）,essential amino acids and non-essential amino acids in muscle were 83.34%-91.13%,35.87%-37.50%and 46.71%-55.23%,respectively.The EAA/TAA of Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus ranged from 39.36%to 45.32%,and the EAA/NEAA ranged from 64.94%to 78.42%.Cyprinus carpio and Carassius auratus met the requirements of FAO/WHO ideal model,and grass carp was slightly lower.The proline（Pro）content of three kinds of freshwater fish in saline-alkali water culture was more prominent,which was significantly higher than that in freshwater culture（P<0.05）.A total of 24 fatty acids,including 8 saturated fatty acids（SFA）,7monounsaturated fatty acids（MUFA）and 9 highly unsaturated fatty acids（PUFA）,were detected in the muscles of the three major freshwater fishes.The ranges of SFA,MUFA and PUFA were 23.04%-28.95%,30.31%-39.36%and 29.80%-34.17%,respectively The ratio of PUFA/SFA was between 1.18 and 1.29.The content of eicosapentaenoic acid（C20:5n3,EPA）and docosahexaenoic acid（C22:6n3,DHA）in muscle is rich,which is a high-quality PUFA dietary source.Principal component analysis showed that there were some differences in the composition of dominant amino acids and fatty acids in the muscles of the three major freshwater fishes,but not significant（P>0.05）.Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus have high nutritional value of amino acids and rich PUFA content,which are high-quality dietary sources.4 Analysis of growth and muscle nutritional quality of native fishesThe SGR,RGR and WGR of Triplophysa yarkandensis cultured in saline-alkali water were 0.57%/d,0.90%/d and 135.56%,respectively,which were higher than those of Cyprinus carpio,Carassius auratus and Ctenopharyngodon idellus.The growth rate fluctuated,with the fastest growth rate from June to July,significantly decreased in August（P<0.05）,and slightly increased in September.The condition factor decreased with the increase of culture time,which was significantly lower than that of bulk freshwater fish（P<0.05）.The relationship between body length and body weight was W=2.7189×10^-4L^2.3544（R²=0.9569）,b=2.3544,showing allometric growth.The crude protein ranged from 25.22%to 25.58%,which was significantly higher than that of freshwater fish（P<0.05）.The content of lysine（Lys）in muscle was high,and the total amount of amino acids was higher than that of FAO/WHO.The EAA/TAA and EAA/NEAA were 41.72%and 71.57%,respectively,which reached the ideal level of FAO/WHO.The contents of PUFA and EPA+DHA in muscle were 32.70%and 4.73%,respectively.Under saline-alkali water culture,the growth traits of Triplophysa yarkandensis were better than those of large freshwater fish.Muscle has high protein content,high quality of amino acids and fatty acids,and good edible value and economic value.