Effects of spectral composition,photoperiod and light intensity on the gonadal development of Atlantic salmon Salmo salar in recirculating aquaculture systems(RAS)

Artificial lighting regimes have been successfully used to inhibit sexual maturity of Atlantic salmon in confinement.However,when these operations are applied in commercial recirculating aquaculture systems(RAS) using standard lighting technology,sexual maturation is not suppressed.In this study,an L_9(3~3) orthogonal design was used to determine the effects of three factors(spectral composition,photoperiod,and light intensity) on the gonadal development of Atlantic salmon in RAS.We demonstrated that the photoperiod at the tested levels had a much greater effect on the gonadosomatic index and female Fulton condition factor than spectral composition and light intensity.The photoperiod had a significant effect on the secretion of sex steroids and melatonin(P<0.05),and a short photoperiod delayed sex steroid and melatonin level increases.The three test factors had no significant effects on the survival rate,specific growth rate,relative weight gain,and male Fulton condition factor(P>0.05).The optimum lighting levels in female and male Atlantic salmon were LD 8:16,455 nm(or 625 nm),8.60 W/m^2;and LD 8:16,8.60 W/m^2,455 nm respectively.These conditions not only delayed gonadal development,but also had no negative effects on Atlantic salmon growth in RAS.These results demonstrate that a combination of spectral composition,photoperiod and light intensity is effective at delaying the gonadal development of both male and female salmon in RAS.

The dissolution of total suspended solids and treatment strategy of tailwater in a Litopenaeus vannamei recirculating aquaculture system

In recirculating aquaculture systems(RASs),the effective treatment of aquaculture tailwater is essential to maintain the health of the RAS.This study investigated the optimal time and method for tailwater treatment during three periods of the aquaculture of the Litopenaeus vannamei:nursery(0–26 d),middle(27–57 d),and later(57–104 d).The variation of several water parameters during the dissolution of total suspended solid(TSS)in tailwater,applied with the effects of ozone on the microorganism and water quality parameters were investigated.Results showed that the TSS concentrations in tailwater decreased with time,although not significantly(P>0.05),whereas total ammonia nitrogen(TAN),nitrite(NO-2-N),and nitrate(NO_(3)^(-)-N)increased significantly(P<0.05).Therefore,TSS should be removed from the tailwater as early as possible,being most optimal within 4 h.Ozone removed 38.24%–48.95%of TSS,17.78%–90.14%of TAN,and 87.50%–98.90%of NO-2-N after 4 h of treatment.However,it resulted in the significant accumulation of NO_(3)^(-)-N.Moreover,the total number of Vibrio and bacterial counts in aquaculture tailwater was reduced completely by ozone within 4 h.Thus,these results provided technical details and data support for the effective treatment of tailwater from shrimp RAS.

Numerical simulation of the hydrodynamics within octagonal tanks in recirculating aquaculture systems

A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system. The realizable k-e turbulence model was applied to describe the flow, the discrete phase model （DPM） was applied to generate particle trajectories, and the governing equations are solved using the finite volume method. To validate this model, the numerical results were compared with data obtained from a full-scale physical model. The results show that： （1） the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks, giving an average relative error of velocities between simulated and measured values of 18% from contour maps of velocity magnitudes; （2） the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank. The average relative error of the removal rates between simulated and measured values was 11%. The DPM can be used to assess the self-cleaning capability of an octagonal tank; （3） a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations. The velocity distribution was uniform with an average velocity of 15 cm/s; the velocity reached 0.8 m/s near the inlet pipe, which can result in energy losses and cause wall abrasion; the velocity in tank corners was more than 15 cm/s, which suggests good water mixing, and there was no particle sedimentation. The percentage of particle removal for octagonal tanks was 90% with the exception of a little accumulation of 〈5 mm particle in the area between the inlet pipe and the wall. This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.

Effect of Hydraulic Loading Rate on the Efficiency of Effluent Treatment in a Recirculating Puffer Aquaculture System Coupled with Constructed Wetlands

Constructed wetlands(CWs) were integrated into an indoor recirculating aquaculture system of obscure puffer(Takifugu obscurus) for effluent treatment. The effect of hydraulic loading rate(HLR) on the efficiency of effluent treatment by CWs was examined for over a month. The CWs were operated under brackish conditions(salinity 7.4–7.6) at 3 different HLRs(0.762, 0.633, and 0.458 m d–1) 3 times, 10 days each. Overall, the CWs exhibited high efficiency in removal of total ammonium nitrogen(by 81.03–92.81%) and nitrite nitrogen(by 99.40%–99.68%). The efficiency of CWs in removal of total ammonium nitrogen, nitrate nitrogen, total Kjeldahl nitrogen, total phosphorous, and total suspended solids(TSS) increased with the decrease of HLR. The CWs operated at the 3 HLRs in a decreasing trend proves to be effective, providing a useful method for effluent treatment in commercial puffer aquaculture systems.

Commercial Production of Tiger Puffer(Takifugu rubripes)in Winter Using a Recirculating Aquaculture System

Tiger puffer(Takifugu rubripes) is a promising species for aquaculture production because of its high value and limited supply. However, in the north of China, using sea cages to culture this species in winter is hampered by the fact that the seawater temperature is extremely low. Here, a large scale commercial production of tiger puffer has been successfully realized using a recirculating aquaculture system(RAS) from 3 October 2012 to 31 May 2013. The RAS was comprised of nine culture tanks(total water volume 200 m3) and stocked with approximately a total of 14400 fish(initial mean weight 160 g). The tiger puffer was hand-fed at a rate of 0.7% of total body weight per day, and the feed conversion rate was(1.21 ± 0.3) kg kg-1. The recycle water in RAS was treated by a sieve bend screen, a foam fractionator, a submerged biofilter, an UV sterilizer and a submersible aerator. During the whole culture period, an excellent water quality control was achieved in RAS. At the end of this experiment, the survival rate of tiger puffer was more than 98%. The final tank densities averaged 31.2 kg m-3, and the final individual mean weight was 440 g.

Stocking density effects on growth and stress response of juvenile turbot(Scophthalmus maximus) reared in land-based recirculating aquaculture system

Stocking density is widely recognized as a critical factor in aquaculture and a potential source of long-term stress.The influence of stocking density on growth and stress response of juvenile turbot（Scophthalmus maximus, ~3–75g, initial to final weight） was examined in fish held under low（LD, ~0.21–5.31 kg/m^2, initial to final density）,medium（MD, ~0.42–10.81 kg/m^2） and high stocking density（HD, ~0.63–14.27 kg/m^2） for 120 days in a recirculating aquaculture system（RAS）. In this trial, the growth curve for weight of juvenile turbot in RAS, all fitted by the Schnute model. No significant difference was found in growth performance among the three densities until at the final sampling（Day 120）. The final weight and body weight increase（BWI） in the HD group were significantly lower than in other groups（P〈0.05, weight：（75.83±2.49） g,（75.39±2.08） g,（65.72±2.86） g and BWI：（2 436.12±28.10）%,（2 421.29±4.64）%,（2 097.88±20.99）% in LD, MD and HD groups, respectively）. Similarly, the specific growth rate（SGR）, feed conversion ratio（FCR） and coefficient of variation for weight（CV_w） were adversely affected by high stocking density（P〈0.05）. However, there was no difference in survival and Fulton＇s condition factor（K） of turbot among the different groups. Physiological analyses demonstrated a clear increase in the plasma cortisol level and an obvious decrease in growth hormone（GH） concentration in the HD group on Day120（P〈0.05）. There was no significant effect of stocking density on plasma glucose, Cl– and protein levels. All these findings would provide a reference for selecting the optimal stocking density of juvenile turbot in RAS.

Effect of copper on the growth of shrimps Litopenaeus vannamei : water parameters and copper budget in a recirculating system

Shrimps( Litopenaeus vannamei) were intensively cultured in a recirculating aquaculture system for 98 days to investigate effects of 0.3 mg/L Cu on its performance, Cu budget, and Cu distribution. Shrimps in Cu-treated systems had greater mean final weight(11.10 vs 10.50 g), body length(107.23 vs 106.42 mm), survival rate(67.80% vs 66.40%), and yield(6.42 vs 5.99 kg/m 3), and lower feed conversion ratio(1.20 vs 1.29) than those in control systems but the differences were not significant. Vibrio numbers remained stable(10 4 –10 6 colony forming units/mL) in the rearing tanks of both control and treated systems. Total ammonium-N, nitrite-N, nitrate-N, pH, chemical oxygen demand, 5-day carbonaceous biochemical oxygen demand, and total suspended solids were similar in controls and treatments. Dissolved Cu concentration in the treated systems decreased from 0.284 to 0.089 mg/L while in the control systems it increased from 0.006 2 to 0.018 mg/L. The main sources of Cu in the treated systems were the artificially added component(75.7% of total input), shrimp feed(21.0%), water(2.06%), and shrimp biomass(1.22%). The major outputs of Cu occurred via the mechanical filter(41.7%), water renewal(15.6%), and draining of the sediment trap(15.1%). The foam fractionator removed only 0.69% of total Cu input. Harvested shrimp biomass accounted for 11.68% of Cu input. The Cu concentration of shrimps in the Cu-treated systems(30.70 mg/kg wet weight) was significantly higher than that in control systems(22.02 mg/kg). Both were below the maximum permissible concentration(50 mg/kg) for Cu in seafood for human consumption in China. Therefore, recirculating systems can be used for commercial on-growing of Litopenaeus vannamei without loss of shrimp quality, even in water polluted by 0.30 mg/L Cu. The mechanical filter is the main route for Cu removal.

Dynamic simulation based method for the reduction of complexity in design and control of Recirculating Aquaculture Systems

In this work we introduce the“Extensible Fish-tank Volume Model”that can reduce the complexity in the design and control of the Recirculating Aquaculture Systems.In the developed model we adjust the volume of a single fish-tank to the prescribed values of stocking density,by controlling the necessary volume in each time step.Having developed an advantageous feeding,water exchange and oxygen supply strategy,as well as considering a compromise scheduling for the fingerling input and product fish output,we divide the volume vs.time function into equidistant parts and calculate the average volumes for these parts.Comparing these average values with the volumes of available tanks,we can plan the appropriate grades.The elaborated method is a good example for a case,where computational modeling is used to simulate a‘‘fictitious process model”that cannot be feasibly realized in the practice,but can simplify and accelerate the design and planning of real world processes by reducing the complexity.

Application of Constructed Wetlands on Wastewater Treatment for Aquaculture Ponds

A group of constructed wetlands （CWs） were applied to the recirculating aquaculture system. This study assessed the performance of CWs in treating the aquaculture wastewater, examined the water quality condition of aquaculture ponds and the growth and the survival rate of ＂target＂ species （Ictalurus punctatus and Megalobrama amblycephala）. The results showed that CWs were effective on reducing the concentrations of 5-day biochemical oxygen demand （BOD5, at 70.5%）, total suspended solids （TSS, at 81.9%）, chlorophyll a （Chl-a, at 91.9%）, ammonium （NH4^＋, at 61.5%） and nitrate nitrogen （NOa-N, at 68.0%）. Effect of CWs on phosphate （PO43 -P） removal was relatively lower （at 20.0%）. The concentrations of BODs, TSS, Chl-a, NH4^＋ and TN, TP in the recirculating culture pond were significantly lower than that in the control pond（ p〈0.05 ）. CWs could help to increase total yield, survival rate of the ＂target＂ species and significantly decrease feed conversion ratio （ p〈0.05 ）.

Optimization and evaluation of a bottom substrate denitrification tank for nitrate removal from a recirculating aquaculture system

A bottom substrate denitrification tank for a recirculating aquaculture system was developed. The laboratory scale denitrification tank was an 8 L tank （0.04 m2 tank surface area）, packed to a depth of 5 cm with a bottom substrate for natural denitrifying bacteria. An aquarium pump was used for gentle water mixing in the tank; the dissolved oxygen in the water was maintained in aerobic conditions （e.g. 〉 2 mg/L） while anoxic conditions predominated only at the bottom substrate layer. The results showed that, among the four substrates tested （soil, sand, pumice stone and vermiculite）, pumice was the most preferable material. Comparing carbon supplementation using methanol and molasses, methanol was chosen as the carbon source because it provided a higher denitrification rate than molasses. When methanol was applied at the optimal COD：N ratio of 5：1, a nitrate removal rate of 4591 ± 133 mg-N/m2 tank bottom area/day was achieved. Finally, nitrate removal using an 80 L denitrification tank was evaluated with a 610 L recirculating tilapia culture system. Nitrate treatment was performed by batch transferring high nitrate water from the nitrification tank into the denitrification tank and mixing with methanol at a COD：N ratio of 5：1. The results from five batches of nitrate treatment revealed that nitrate was successfully removed from water without the accumulation of nitrite and ammonia. The average nitrate removal efficiency was 85.17% and the average denitrification rate of the denitrification tank was 6311 ± 945 mg-N/m2 tank bottom area/day or 126 ± 18 mg-N/L of pumice packing volume/day.

拟穴青蟹循环水养殖系统生物滤池细菌群落变化

【目的】探究拟穴青蟹(Scylla paramamosain)循环水养殖系统(Recirculating aquaculture systems,RAS)生物滤池启动过程中细菌群落的演替过程,为设计适合拟穴青蟹RAS养殖的生物过滤器提供指导。【方法】在2、5、10、20、30、40、50 d检测RAS养殖池的水质,采集填料生物膜和养殖池水体微生物样品,采用多种生物信息学分析方法研究生物膜微生物群落演替过程,并运用实时荧光定量PCR技术检测生物膜碳循环和氮循环功能基因拷贝数。【结果与结论】氨氮(NH4+-N)、分子氨(NH3)和亚硝态氮(NO2--N)的质量浓度总体呈先上升后下降趋势,硝态氮(NO3--N)和总氮(TN)在实验结束时(50 d)积累,总有机碳(TOC)质量浓度在前10 d保持稳定,从10 d至50 d呈先升高后下降趋势,差异显著(P<0.05),且总氮和硝态氮质量浓度对生物膜细菌群落变化的影响最大。生物膜细菌群落的多样性、均匀性和丰富度在10 d达到峰值,然后达到平稳状态。基于FAPROTAX的功能预测发现生物膜大多数功能主要富集在氮循环和有机物降解这两方面,生物膜碳循环和氮循环绝对基因拷贝数随时间增加总体呈升高趋势。根据FEAST分析结果,除10 d以外,前20 d同一时期的水体细菌对生物膜的贡献较高,后30 d主要来源于生物膜本身前期细菌贡献,且贡献率随时间增加呈增长趋势,到后期趋于稳定。结果表明,拟穴青蟹RAS生物滤池启动过程中,生物膜的细菌群落结构随时间增加变化显著,功能主要富集在氮循环和有机物降解这两方面,生物膜细菌来自本身细菌的贡献率也逐渐升高,到后期趋于稳定。

工厂化循环水养殖系统重金属积累的生物毒性及去除技术

养殖水产品需求日益增高,传统水体养殖技术无法满足市场需求,由此诞生了高产低碳的循环水养殖技术,但其作为一个高密度养殖的封闭/半封闭系统对水质要求很高。循环水经处理后残余并积累的重金属污染物会给养殖系统带来安全隐患,不仅会积累于水产品体内对其造成生物毒性或直接导致其中毒死亡,还会通过食物链传递对人类健康造成威胁。如何在保持水产品的高产率下去除循环水中积累的重金属污染物是未来技术发展需要重点解决的问题。对循环水养殖系统中循环积累产生的重金属污染物的持续性危害和处理技术进行了分析和总结,预测了未来研究的突破方向,以期为去除水体重金属技术的发展提供参考。

饲料粘合剂对刺参循环水养殖水质、生长及肠道微生物的影响

为探究刺参(Apostichopus japonicus)循环水养殖系统中不同饲料粘合剂对系统水质及刺参生长和肠道微生物的影响,设置了无粘合剂添加的对照组(D1)和分别添加5%红薯淀粉(D2)、黄原胶(D3)、瓜尔胶(D4)、卡拉胶(D5)的4个处理组,每组设3个重复。采用(20.0±5.0)g规格的刺参,在循环水养殖系统中饲养42 d,测定养殖水质、刺参体质量和肠道微生物组成,并运用Kruskal-Wallis秩和检验对刺参肠道微生物进行组间差异显著性分析,采用冗余分析和典型关联分析对水质与肠道微生物进行相关性研究。结果显示:粘合剂的添加对水质有优化作用,其中瓜尔胶组水质最佳;红薯淀粉和瓜尔胶组的刺参特定生长率和饲料转化率显著高于其他组(P<0.05),且刺参出皮率较高。刺参肠道优势菌门为变形菌门、拟杆菌门等,优势菌科为弧菌科、红杆菌科等。红薯淀粉组的刺参肠道微生物丰富度和多样性最高,且肠道中黄杆菌科等有益菌丰度升高。水质与刺参肠道微生物存在显著相关性,在科水平上,氨氮、亚硝酸盐氮、硝酸盐氮与弧菌科、希瓦氏菌科呈正相关,与黄杆菌科、肠杆菌科呈负相关。研究表明:综合考虑水质、刺参生长及肠道微生物情况,在刺参饲料中选择红薯淀粉或瓜尔胶作为粘合剂,更有利于刺参的健康养殖及循环水养殖系统中良好水质的维持。

虎龙杂交斑循环水育苗系统设计及应用效果

为了进一步研究封闭式循环水养殖系统在海水鱼育苗生产过程中应用的可行性,采用物质平衡相关原理,结合循环水养殖水处理设施设备构建技术,优化了水处理工艺流程并设计了生物滤器体积与循环量等关键参数,构建了一套封闭式可控型循环水育苗系统。设计了2路水处理环路,集成构建了育苗池双排水、竖流沉淀、移动床生物过滤等高效水处理技术和装备。使用该育苗系统开展虎龙杂交斑(Epinephelus lanceolatus♂×E.fuscoguttatus♀)育苗试验,重点考虑溶氧、pH和氨氮3个水质指标及全长、体质量和出苗率3个生长指标。结果显示:仔稚鱼生长情况良好,平均全长(75.1±0.55)mm,平均体质量(9.2±0.42)g,出苗率16.28%。水质检测结果显示:温度26.8~27.7℃,溶氧6.6~7.2 mg/L,pH平均为8.31、总氨氮平均质量浓度为(0.183±0.191)mg/L,水质情况良好。经济性分析结果显示:单茬利润1.86万元,年利润5.58万元(按1年3茬计),具有良好的经济效益。该研究可为工厂化循环水育苗系统应用及推广提供技术支持。

鱼类趋流性在循环水养殖系统中的应用与展望

鱼类的游泳行为是一个复杂的过程,受到多种因素(包括生理因素和环境因素)的影响,其中水流是主要的环境影响因素之一。鱼类可以综合利用多种感觉器官感知水流的方向和速度,通过摆尾运动维持自身稳定,使其逆流而上或顺流而下或原地游动,以适应复杂的水流环境。人们将这种鱼类对水流的反应特性命名为“趋流性”。

一种三回路式淡水循环养殖系统的构建及应用

为满足人们对优质鱼类蛋白日益增长的需求和环保要求,在海南琼海构建了三回路式高密度循环水养殖系统,以微滤机反冲洗水作为反硝化碳源,建立了水循环处理、鱼粪污泥厌氧消化对鱼类生长和污染物控制的运行方式。在121 d的吉富罗非鱼(Oreochromis mossambicus)养殖实验中,养殖密度达到107.7kg·m^(-3),存活率100%,饲料转化率(FCR)1.74;鱼缸中总氨氮(TAN)、亚硝酸盐氮(NO_(2)^(-)-N)和硝酸盐氮(NO_(3)^(-)-N)的平均浓度分别为0.95、0.15和43.01 mg·L^(-1)。每日外排水量为系统总水量的2.66%、养殖水量的6.67%;试验期间,厌氧消化单元内仅有少量污泥残留而无外排。微生物群落分析表明,共21个菌属参与了氮代谢,包括红细菌属(Rhodobacte)、黄杆菌属(Flavobacterium)和固氮螺旋菌属(Azospira)等。结果表明,该循环水养殖系统为罗非鱼等淡水鱼类养殖提供了一种潜在的生态可持续循环养殖模式。

2种海水鱼工厂化循环水养殖中微细颗粒物的赋存特征

为了明晰工厂化循环水处理系统对水中微细颗粒物的去除效果,对红鳍东方鲀(Takifugu rubripes)和半滑舌鳎(Cynoglossus semilaevis)工厂化循环水养殖过程中微细颗粒物的质量、组成和粒径分布的动态变化进行研究。结果表明,基于弧形筛、泡沫分离器和生物滤池的工厂化循环水处理工艺,红鳍东方鲀和半滑舌鳎养殖池水中微细颗粒物浓度均稳定在20 mg·L^(-1)左右,且投喂后水中微细颗粒物含量明显增高,微细颗粒物中有机物所占比例均达到90%以上,表明水中微细颗粒物增多是投喂所致。红鳍东方鲀养殖池水中微细颗粒物的粒径主要分布在60~170 nm,半滑舌鳎养殖池水中微细颗粒物的粒径为95~420 nm。养殖池出水经水处理系统处理后,水中留存的微细颗粒物的粒径主要介于95~110 nm之间,表明该循环水养殖系统中粒径在60~95 nm之间和粒径大于110 nm的微细颗粒物可以被有效去除。

基于文献计量分析循环水养殖发展

为了更清晰了解循环水养殖领域研究的演化、现状、趋势和热点,基于Web of Science、中国维普、中国知网等数据库进行检索,利用文献计量法对1992—2023年循环水养殖相关文献进行数据分析与挖掘,并结合CiteSpace软件对结果进行可视化分析。结果表明:(1)循环水养殖研究逐渐被各国、各机构、各高校重视,研究成果较多;(2)欧美发达国家在1998—2001年已开始研究循环水养殖,起步较早、发文量最高;(3)中国知网收录作者发文量最高,作者及机构合作密切,研究热点集中在渔业器械、装备自动化等方面。本研究成果可为构建高质量、低能耗、智能化的工业化循环水养殖系统提供数据支撑。

一家典型海水工厂化循环水养殖系统运行效果分析——以半滑舌鳎为例

循环水养殖系统作为一种新型高密度养殖方式具有养殖水体环境可控、系统运行平稳、技术安全可靠、高度节水节地等优点。本文以天津市滨海新区某企业养殖半滑舌鳎为例,对循环水养殖系统的运行效果进行分析。结果表明:半滑舌鳎的养殖密度为(20~25)kg/m^(2),初始平均质量为5 g,利用循环水养殖系统养殖407 d,最终平均质量为1079 g,存活率为29.1%。通过水质检测分析,氨氮平均去除率为64%;亚硝酸盐平均去除率为58%;弧菌和细菌的灭杀率为99%;pH值保持在7.0~8.5;盐度维持在18~35。经济性分析结果表明,该海水工厂化循环水养殖系统的可行性和经济性良好,适宜在沿海地区大力推广。

人工海水条件下移动床生物膜反应器快速挂膜启动试验

海水循环水产养殖系统中,生物膜反应器的挂膜时间通常较长。为实现人工海水条件下移动床生物膜反应器(moving-bed biofilm reactor,MBBR)滤片的快速挂膜,通过搅拌滤片,采用低成本的海水配方、专用营养液以及选择多样化的菌种等方法和措施进行了试验,并建立了以氨氮、亚硝酸盐氮水平、滤片颜色和孔隙生成物为指标的评估体系。试验结果表明,相比于化学营养组的56 d,发酵营养组经过46 d即完成了挂膜。挂膜过程中氨氮质量浓度最高为20.36~25.12 mg/L,亚硝酸盐氮质量浓度最高为45.28~53.20 mg/L。