投喂频率对工厂化循环水养殖星康吉鳗生长、生理指标及其水质的影响

Effects of Feeding Frequency on the Growth,Physiological Indices,and Water Quality of Conger myriaster Reared in Industrial Recirculating Aquaculture Systems

本研究采用生理学和实验生态学方法探究了工厂化循环水养殖模式下,不同投喂频率对星康吉鳗(Conger myriaster)生长、生理指标以及水质因子的影响。选用初始体重为(150.64±5.43)g的星康吉鳗为研究对象,实验共设2组,分别为1次/天(T1组)、2次/天(T2组),每组3个重复,实验周期为70d。实验每14d检测各养殖池实验鱼平均体重和循环水系统水质指标;实验结束时,采集星康吉鳗血液、组织相关样品,用于生长、生理指标的测定与分析。结果显示,T2组终末体重(FBW)、终末体长(FBL)、增重率(WGR)、特定生长率(SGR)显著高于T1组(P<0.05),T1组饲料系数(FCR)显著高于T2组(P<0.05)。T1组血清丙二醛(MDA)显著高于T2组(P<0.05),T2组肝脏谷草转氨酶(AST)、肝脏谷丙转氨酶(ALT)、肠道胰蛋白酶(TPS)显著高于T1组(P<0.05)。T1组、T2组出口水NH_(4)^(+)-N、NO_(2)^(-)-N 24 h变化中分别有1处(24:00)和2处峰值(20:00、次日8:00);2个实验组出口水24 h内NH_(4)^(+)-N与生物滤池出口水差异显著(P<0.05);生物滤池出口水NO_(2)^(-)-N在04:00、08:00显著低于其他2个实验组出口水(P<0.05);T2组2种指标的24 h变化幅度均小于T1组。整个实验周期内各水质指标均维持在安全养殖范围内,其中,在第70天时,T2组总氮(TN)、总磷(TP)显著高于T1组(P<0.05);生物滤池对各项水质指标处理效果各不相同,其中,对NH_(4)^(+)-N的处理效果最佳,最高可达54.23%。基于上述结果,星康吉鳗幼鱼工厂化循环水养殖模式中,2次/天的投喂效果优于1次/天。相关结果为星康吉鳗工厂化循环水养殖模式中适宜的投喂策略提供了理论参考。

The whitespotted conger(Conger myriaster)is an important fish species with high economic value in China and Japan owing to its high nutritional content.It occupies an important position in marine-eel export in China.C.myriaster has the potential to be artificially cultured and has promising economic prospects.Thus,there is growing international interest in C.myriaster research.Indeed,to meet the demands of domestic and foreign markets,artificial culturing of C.myriaster is urgently required.However,at present,there is no report on the research of C.myriaster reared in industrial recirculating aquaculture systems.Feeding frequency has been reported to affect feed intake and growth performance in a number of fish species.Feed management in terms of optimization of feeding frequency has emerged as one of the crucial areas of research in the field of aquaculture.Overfeeding and leftover food disrupts the water quality,while inadequate food supply has direct impact on production cost.Traditional flow through systems uses large volumes of water,and intensified aquaculture has drawbacks,such as large amount of discharged waste from effluent water.Among the excreted nutrients,nitrogen and phosphorus constitute the largest proportion.Sustainability with low environmental impacts is one of the concerns when developing aquaculture systems.Based on the concepts of reduced water consumption and efficient water management,recirculating aquaculture systems offer the possibility of creating a sustainable future for fish production.Thus,a 70-day experiment was conducted to investigate the effects of different feeding frequencies and water quality on the growth performance and physiological and biochemical indices of C.myriaster[body weight:(150.64±5.43)g]reared in industrial recirculating aquaculture systems;physiological and ecological methods were used in this study.The experiment comprised two feeding frequency groups,feeding once(group T1)and twice(group T2)per day,and each treatment group had three replicates.The average body weight of the fish in each culture pond and the water quality indices of the culture system were measured and analyzed every 14 d.At the end of the experiment,the blood,liver,and intestine samples of C.myriaster were collected to determine and analyze growth and physiological indices.The results indicated that(1)the growth performance of group T2 was better than that of group T1.The final body weight,final body length,weight gain,and specific growth rate of group T2 was significantly higher than those of group T1(P<0.05).The feed coefficient of group T1 was significantly higher than that of group T2(P<0.05).However,no significant differences were found in the final body height,liver body ratio,visceral body ratio,condition factor,or survival rate at different feeding frequencies(P>0.05).(2)The serum malondialdehyde of group T1 was significantly higher than that of group T2(P<0.05).The hepatic alanine aminotransferase and hepatic aspartate transaminase of group T1 was significantly higher than those of group T2(P<0.05).The intestinal trypsin of group T2 was significantly higher than that of group T1(P<0.05).There were no significant differences in the levels of serum superoxide dismutase,serum catalase,intestinal amylase,or intestinal lipase between groups T1 and T2(P>0.05).(3)In the 24 h changes of ammonia nitrogen(NH_(4)^(+)-N)and nitrite nitrogen(NO_(2)^(-)-N),the change patterns of the two indices in outlet of the T1 group were similar to those of the outlet of the bio-filter;the two indices of the outlet water in T1 and T2 groups were one(24:00)and two peaks(20:00 and 08:00)respectively;the difference in NH_(4)^(+)-N in the outlet water of the two test groups within 24 h was significant(P<0.05);at 04:00 and 08:00,the NO_(2)^(-)-N content of the outlet water of the biofilter was significantly lower than that of the other two test groups(P<0.05);the 24 h changes range of NH_(4)^(+)-N and NO_(2)^(-)-N in T2 group were smaller than those in T1 group.(4)During the whole test period,each water quality index was maintained within the safe breeding range,and no significant differences were found in NH_(4)^(+)-N,NO_(2)^(-)-N,chemical oxygen demand,and active phosphate concentration between T1 and T2 groups(P>0.05);at the end of the test,the total nitrogen and total phosphorus of T2 group were significantly higher than those of T1 group(P<0.05);the biofilter has different treatment effects on various water quality indices,among which the treatment effect on NH_(4)^(+)-N is the most efficient,up to 54.23%.Based on the above results,the feeding frequency of twice per day was better than that of once per day in the industrial recirculating aquaculture mode for C.myriaster(body weight:150~250 g).Without affecting the survival rate and condition factor,the twice per day group can save costs and improve economic benefits.However,due to the limitations of the test conditions,we did not explore more times of feeding,and further tests are needed in the future.The predominance,which was the high efficiency of water qualities treatment and optimal effect of culture,was demonstrated obviously in closed recirculating aquaculture systems.This study aims to provide a theoretical reference for the appropriate feeding strategy in the industrial recirculating aquaculture model of C.myriaster.