Experimental investigation on the transport of different fish species in a jet fish pump

A jet fish pump with a throat of ø60 mm was designed to study its performance in the transport of different fish species and the physiological changes in fish thereafter. Experiments were conducted to investigate the fish transport rate and energy required to transport each ton of fish when transporting Carassius auratus, commonly known as the Chinese goldfish, Megalobrama amblycephala, or Wuchang bream, and Ctenopharyngodon idella, the grass carp. Fish were examined for external injuries as well as for several important enzymes and hormones which are indicators of tissue injury and stress. The results showed that the transport rate for all three species of fish rose dramatically with an increase in the primary stream rate. In this experiment, the transport rates of C. auratus, M. amblycephala and C. idella reached 2357 ± 37.2 kg ∙ h⁻¹, 2888 ± 41.6 kg ∙ h⁻¹, and 2060 ± 40.2 kg ∙ h⁻¹, respectively. However, both injury rate and energy required to transport each ton of fish increased no matter whether the primary stream rate was too low or too high. Considering both transport rate and injury rate, the mean primary stream rate of 80 m³ ∙ h⁻¹ was determined to be the optimal operating condition in this experiment. Fish were stressed and most likely some of their organs were damaged. However, most physiological indexes almost fully recovered after several hours.     

Engineered-airlift pumps for aquaculture applications using multiphase flow analysis

Currently, very few aquaculture operations are employing airlift pump technology for water recirculation, aeration, and waste removal. This is likely due to the poor design and lower efficiency of traditional airlift design, the limited amount of research effort that has been invested in improving performance capabilities of air lift pumps and the general lack of awareness of the industry about the inherent advantages of airlift systems. A new efficient airlift pump is hydrodynamically designed by incorporating the Volume of Fluid (VOF) multi-phase model along with the K-ε turbulence model utilizing Computational Fluid Dynamics (CFD) tools. The pump is designed to offer a substantial reduction in total energy usage as well as an improved quality of the culture products in order to make it attractive to aquaculture industry. In this study, both numerical and experimental investigations were carried out for airlift systems operating under two different submergence ratios of 50% and 90% in a lab setting using 2.54 cm diameter pumps. Also, the performance of a large-scale pumps of 10.16 cm diameters were also tested in an aquaculture raceway to determine its effect on the operation. The numerical results were found to be in agreement with the experiments within ±20% which is considered very reasonable for multiphase flow analysis. The present study was found to present a great tool for modelling the airlift pump performance, and potentially proposing new designs.     

杂交条纹鲈苗种小水泥池培育技术试验

用地上露天小水泥池8个．进行杂交条纹鲈苗种培育试验．放养313龄水花30000尾．通过天然饵料、藻粉投喂以及适当水质管理措施．经32天培育，共培育3．5～4．6cm体长的鱼种4336尾．最高成活率为19．1％，最低为6％，平均为14．5％。     

富藻养殖水体中金鱼藻和篦齿眼子菜的抑藻效果研究

夏季高温时,养殖水体水华现象频繁发生,给养殖业带来巨大的损失。常见水生植物释放的活性物质在低浓度下可以起到抑藻作用,对藻类调控具有重要意义。本研究采用实验室静态模拟方法,取养殖池塘暴发蓝藻水华的水体,与沉水植物金鱼藻(Ceratophyllum demersum)及篦齿眼子菜(Potamogeton pectinatus)进行共培养,研究这2种沉水植物对养殖水华水体营养水平、藻类生长、藻类结构及浮游藻类生物多样性的影响。结果显示,金鱼藻和篦齿眼子菜可显著降低水华水体氮、磷等营养水平(P<0.05);金鱼藻和篦齿眼子菜可有效抑制水华蓝藻(Cyanobacteria)生长,尤其对颤藻和微囊藻(Microcystis sp.)效果显著(P<0.05),且篦齿眼子菜对水华蓝藻抑制效果更为显著。实验结束时,篦齿眼子菜培养组藻密度下降93.6%,生物量下降98.9%,叶绿素a含量下降60.5%;金鱼藻培养组藻密度下降72.5%,生物量下降86.8%,叶绿素a含量下降54.3%;金鱼藻和篦齿眼子菜的存在可促进养殖水体浮游藻类生物多样性增加,且金鱼藻提高浮游藻类生物多样性效果更显著。金鱼藻培养组浮游藻类生物多样性升高98.4%,篦齿眼子菜培养组浮游藻类生物多样性升高50.3%。本研究结果可为未来生态养殖提供理论依据和参考。     

生物海绵铁复合填料曝气生物滤器处理养殖海水脱氮条件优化研究

为了提高海水循环养殖系统(RAS)中曝气生物滤器(BAF)系统脱氮效率,减少亚硝态氮(NO^2--N)积累和曝气量,将铁基复合生物填料引入BAF系统,以间歇式曝气营造BAF系统好氧、缺氧和厌氧的循环环境,采用扫描电子显微镜考察了填料表面形态,研究了不同复合填料配比及曝气运行方式下的氮污染物的处理效果,并利用单因素实验对生物滤器的各重要运行参数进行优化。结果显示,添加铁基填料可以提高约10%的脱氮效率,降低25%的NO^2--N积累并节省50%的曝气量;海水BAF系统在如下运行参数条件下有更优的去除性能,间歇曝气时长为12 h,聚碳酸亚丙酯(PPC)凝胶亲水填料与海绵铁复合配比为3∶1,温度为30℃,水力负荷率(HLR)为1.2 m^3/(m^2·d),进水氨氮(NH4^+-N)负荷为1 mg/L。研究表明,在RAS中引入铁基填料并以间歇曝气方式运行,能提高BAF系统处理氮污染物效率,明显降低NO^2--N积累和运行耗电量,为BAF在RAS中的生产应用提供理论依据。     

宁夏地区不同模式养殖池塘夏季浮游微藻群落特征

为研究宁夏地区夏季不同模式养殖池塘的浮游微藻群落结构特征,采集了当地棚塘接力养殖(PT)、稻渔种养(DY)、土池养殖(TC) 3种模式的池塘水体样品,分析了其浮游微藻群落组成及其与水质因子的相关性。结果显示,共检出浮游微藻5门27属,总数量为1.52×104~2.39×108 ind./L,生物量为0.16~97.78 mg/L,数量多样性为0.03~3.31,生物量多样性为0.29~3.58。不同模式池塘的浮游微藻群落结构差异显著。PT模式池塘的微藻群落无明显共性特征,蓝藻(Cyanophyta)、绿藻(Chlorophyta)和硅藻(Bacillariophyta)占优势情况均有出现,如拟鱼腥藻(Anabaenopsis sp.)、鱼腥藻(Anabaena sp.)、颤藻(Oscillatoria sp.)、盘星藻(Pediastrum sp.)、卵囊藻(Oocystis sp.)、小环藻(Cyclotella sp.)等;TC模式池塘的微藻优势属单一,分别以盘星藻、小球藻(Chlorella sp.)和微囊藻(Microcystis sp.)占优势;DY模式池塘的微藻多样性丰富,以小球藻、栅藻(Scenedesmus sp.)、盘星藻、卵囊藻、刚毛藻(Cladophora sp.)等绿藻和小环藻、菱形藻(Nitzschia sp.)等硅藻为优势藻。蓝藻生物量与水体中硝酸盐氮(NO3–-N)、亚硝酸盐氮(NO2–-N)、化学需氧量(COD)浓度呈显著正相关(P<0.05)。研究表明,宁夏地区夏季温度高、光照时间长,池塘水体中C、N营养高,易形成以微囊藻、拟鱼腥藻等有害蓝藻优势种群;调控池塘水质时应将其作为关键控制点之一,防控有害藻华暴发而导致减产降效的不良状况发生。     

投喂率对凡纳对虾中间培育生长、生理和水环境的影响

中间培育是凡纳对虾(Penaeus vannamei)养殖的重要阶段,投喂率是影响此阶段养殖成效的重要参数。本研究开展为期30 d的养殖实验,研究3组投喂率(投喂率分别为体重的5%、7.5%、10%,分别命名为T5、T7.5和T10)对凡纳对虾中间培育养殖水质、微生物群落结构、非特异性免疫指标及生长性能的影响。实验期间,水体pH、盐度、温度及溶解氧均保持在适宜对虾生长的范围内。结果显示,随着实验进行,总氨氮(TAN)、亚硝态氮(NO2–-N)和化学需氧量(COD)浓度出现上升趋势,实验结束时,其浓度随投喂率升高呈现显著差异：T10>T7.5>T5。微生物群落结构分析表明,养殖水体的微生物群落丰富度和多样性随投喂率升高呈下降趋势,不同投喂率的优势门类均为变形菌门(Proteobacteria, 50.36%~67.53%)和拟杆菌门(Bacteroidetes, 12.09%~67.53%);在属水平上,对凡纳对虾有害的弧菌(Vibrio)相对丰度在T10组最高(37.33%)、T5组最低(0.13%);对其有益的假交替单胞菌(Pseudoalteromonas)相对丰度在T10组最低(0.28%)、T7.5组最高(9.78%)。凡纳对虾肝胰腺的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、酸性磷酸酶(ACP)和碱性磷酸酶(AKP)活性在T10组最低、T7.5组最高(P<0.05)。T7.5和T10组对虾的体长和体重均显著大于T5组(P<0.05),但T7.5和T10组之间无显著差异(P>0.05),投喂率与存活率呈负相关,且3组间存在显著差异(P<0.05)。利用因子分析对非特异性免疫指标和生长指标进行综合评价,结果表明,T7.5组得分最高,为0.92,凡纳对虾中间培育的投喂率在7.5%左右为宜。     

进水流速对圆形循环水养殖池流场特性影响的数值模拟

通过对工厂化循环水养殖进水流速的智能调控,可降低饵料残留,避免水质恶化。为此,本研究采用数值模拟方法探究了进水流速对工厂化循环水养殖池流场特性的影响,并基于该研究设计出一套确定进水流速调控的实验方法。首先,通过对比Standard k-ε、RNG k-ε和Realizable k-ε 3种湍流模型及多种壁面函数的仿真效果,确定RNG k-ε模型和标准壁面函数作为仿真配置。同时,针对多相流模型,对欧拉多相流模型和DPM离散相模型进行对比,为提高计算准确性选用DPM离散相模型,并基于上述模型进行网格无关性验证、制定网格划分方案。其次,以大菱鲆(Scophthalmus maximus)养殖为例,模拟不同进水流速下养殖池流场、排污和水温调节的效果。最后,针对仿真结果提出进水流速调控方案。结果显示,日常采用1.0 m/s的进水流速,可有效提高适宜流速区面积并控制水处理成本;投饵前,采用0.2 m/s的进水流速可以解决循环水养殖中存在的饵料浪费问题;进食结束后,采用1.2 m/s的进水流速可快速排出残饵避免水质恶化;水温异常时,采用15 ℃的水、以1.2 m/s的进水流速注水230 s,可使20 ℃的水下降到正常水平,精准化控制水温。采用本研究提出的方法,可针对不同养殖生物和养殖环境设计进水流速智能调控策略,可用于解决循环水养殖过程中饵料浪费、水质变差和水温异常等问题。     

美洲鲥当年鱼种池塘大棚越冬养殖试验

于2017—2019年采用在池塘上方搭建简易保温大棚的方式开展了美洲鲥当年鱼种越冬养殖试验,研究探讨了越冬养殖相关的技术参数。结果显示:搭建保温大棚后,冬季池塘水温可保持在10℃以上,在美洲鲥当年鱼种(0+龄鱼种,平均体长12.45~16.65 cm,平均体质量27.29~66.41 g)放养密度为1518~2970尾/亩(15亩=1 hm^2,下同)和81.04~100.78 kg/亩的条件下,在越冬前中期(12月至次年3月中旬),日投饲量在0.8~1.6 kg/亩,越冬后期(次年3月中旬至4月上中旬),日投饲量也由2.0 kg/亩左右迅速增加到4.0~5.0 kg/亩。经过125~130 d的越冬养殖,鱼种平均体长达17.48~21.19 cm,增长28.04%~40.40%,平均体质量77.57~137.96 g/尾,增加了106.53%~184.24%,鱼种的体长和体质量特定生长率分别为(0.193~0.261)%/d和(0.585~0.804)%/d,日均增长量和日增重分别为0.036~0.039 cm/d和0.387~0.572 g/d;收获时美洲鲥鱼的肥满度为1.42~1.43 g/cm3,养殖成活率为89.29%~94.81%,饲料系数为1.50~1.65,亩产量为198.50~205.68 kg。试验结果表明,在江浙地区,养殖池塘上方搭建保温大棚后,冬季池塘水温(10~20℃)在美洲鲥当年鱼种的适宜水温范围,能获得较理想的越冬养殖效果。     

净水复合菌在海蜇池塘生态养殖中的应用

将光合细菌、芽孢杆菌、乳酸菌、酵母菌和硝化细菌等组成的复合菌,应用于海蜇池塘养殖中。结果显示:水中复合菌密度为16×10~6个菌体/ml以上时,能分解海蜇和刺参的粪便;在养殖池塘中,按2kg/1000m~3的用量、施加密度为10×10~8个菌体/ml的复合菌液,可降低养殖水体中的氨氮含量,增加池塘中的单胞藻、桡足类和多毛类幼体等浮游生物的数量。表明净水复合菌能有效地改善养殖生态环境,从而促进海蜇的生长。