Effect Of Rearing Density On Growth Performance Of Gibel Carp Cultured At The Land-based Round Tank Aquaculture Model

In this experiment,we studied the effects of different culture densities on the growth performance and muscle quality of Carassins gibelio var.casⅤin the land based round tank aquaculture mode.Two density groups were designed,high density group（1.13kg/m³）and low density group（0.84 kg/m³）.Three parallel barrels were set in each density group.The experiment fish were randomly divided into 13.9±0.2g/tail.We spent 210 d to finished the experiment,than we analyzed the growth performance,muscle quality,serum,liver physicochemical indexes,water quality,and aquaculture benefits of the experiment fish.The results are as follows:1.At the end of culture experiment,the weight gain of HSD group and LSD group was 4.31 times and 5.7 times.The final body weight（FW）,final body length（FL）,weight gain rate（WGR）,specific growth rate（SGR）and ingestion rate（IR）in LSD group were significantly higher than those in HSD group（P<0.05）,and the feed conversion ratio（FCR）in LSD group was lower than that in HSD group.The expressions of myog,myod,mrf4 and igf-1r in LSD group were significantly increased（P<0.05）.2.The freezing exudation rate and water loss rate of muscle in HSD group were significantly higher than those in LSD group（P<0.05）,the muscle hardness in LSD group was significantly higher（P<0.05）,and there were no significant differences in elasticity,recovery,cohesivity,adhesivity and chewability between the two groups.The muscle fiber density in LSD group was significantly higher（P<0.05）.The muscle moisture content,ash content and crude lipid content in LSD group were significantly higher（P<0.05）,but there was no significant difference in muscle crude protein content between the two groups.3.Serum concentrations of alanine aminotransferase（ALT）,triglyceride（TG）,lactic acid（LD）and Cortisol（Cortisol）in HSD group were significantly increased（P<0.05）.There were no significant differences in serum concentrations of glucose（GLU）,cholesterol（CHO）,alkaline phosphatase（ALP）and aspartate aminotransferase（AST）between the two density groups.The concentrations of catalase（CAT）and malondialdehyde（MDA）in liver of HSD group were significantly increased（P<0.05）.4.During the culture period,the dissolved oxygen of the two groups showed a downward trend,and there was no significant difference.At 147 d,the dissolved oxygen dropped to the lowest level of 4.41 mg/L,and the p H value of the two groups was always weakly alkaline.The concentrations of TP,TN and N0^2-in the two density groups increased first and then decreased.The concentrations of TP and N0^2-in HSD group were significantly higher than those in LSD group（P<0.05）,and the concentrations of NH⁴⁺-N and N0^3-showed an increasing trend in both density groups,without significant correlation.5.At the end of breeding,the fish produced by HSD group was 1,650 kg,the net profit was 1,100￥,and the return on investment was 5.89%.The fish produced by LSD group was 1,550 kg,the net profit of LSD group was 2,700￥and the return on investment was 16.98%.The breeding cost of HSD group was 18,700￥,and that of LSD group was15,900￥.The breeding cost mainly included fish fry,animal protection products,electricity cost,feed and labour cost.The results showed that the fish in the LSD group had rapid growth,high feed utilization rate,good muscle quality,strong antioxidant capacity and high economic benefit.The appropriate breeding density can improve the breeding effect and economic benefit of the breeding objects.