Effects of Panax ginseng extract in practical diets for rainbow trout (Oncorhynchus mykiss) on growth performance,immune response and resistance to Yersinia ruckeri

In a preliminary in vitro study, a Panax ginseng extract exhibited an evident antibacterial activity against Yersinia ruckeri and Lactococcus garvieae and affected the respiratory burst and proliferation of rainbow trout Oncorhynchus mykiss leukocytes. Subsequently, the effects of a dietary ginseng extract supplementation on growth, blood biochemical profile, innate immune response and resistance against Y. ruckeri infection were investigated in vivo in rainbow trout juveniles. Four experimental diets were obtained by adding 0.0%, 0.01%, 0.02%, 0.03% of ginseng ethanolic extract to a commercial feed. Each diet was fed to triplicate groups of fish (mean body weight 30.5 ± 0.15 g) at 1% of body weight day^?1 for 10 weeks. The dietary supplementation with ginseng extract did not affect growth performance, feed utilization, biometric traits and fish whole body composition (P > 0.05). No major changes due to graded levels of ginseng extract in the diet were observed in blood biochemical parameters except for increasing plasma triglycerides and non‐esterified fatty acids in fish fed diets including 0.01% and 0.02% of extract (P < 0.05). The innate immune response was barely modulated by the dietary addition of ginseng extract. Serum lysozyme and leukocytes respiratory burst activities were just slightly increased in fish fed all the ginseng extract‐supplemented diets compared with controls, whereas serum antiproteases and leukocyte MPO were not affected (P > 0.05). The dietary administration of ginseng extract induced a reduction in mortality of rainbow trout infected with Y. ruckeri, although no significant differences between treated and control groups were observed (P > 0.05).     

Effects of stocking density on the performance of brown shrimp Farfantepenaeus californiensis co‐cultured with the green seaweed Ulva clathrata

The brown shrimp Farfantepenaeus californiensis and the seaweed Ulva clathrata, both native to north‐west Mexico, were co‐cultured in lined ponds during 18 weeks. The aim of this study was to evaluate different stocking densities (10, 20, 30, 40 and 50 per m²) in terms of shrimp yield to see if the co‐culture method results in shrimp yields suitable for commercial production. The presence of Ulva results in good water quality and allows culture of brown shrimp with low water exchange (10% weekly) and with low nitrogen and phosphorus content in discharged water. The final weight and specific growth rate (SGR) in shrimp between 10 and 30 per m² were significantly higher (12.5–12.0 g and 4.56–4.53% day⁻¹ respectively) than 40 and 50 per m² (9.1 and 8.6 g, and 4.31% and 4.26% day⁻¹ respectively). Total shrimp biomass generated in 30 or more shrimp per m² was significantly higher (2.7–3.1 t ha⁻¹) compared with 10 and 20 shrimp per m² (1.0 and 2.0 t ha⁻¹ respectively). The lowest feed conversion ratio (FCR) (0.97) was shown in the 10 shrimp per m² case, and the highest FCR was seen with 50 shrimp per m² (1.37). Shrimp survival ranged between 71% and 81%, where the highest mortality was shown in 50 shrimp per m². The results show that the co‐culture method can result in commercially interesting yields, suggesting that 30 shrimp per m² is the best stocking density for co‐culturing F. californiensis with U. clathrata, based on the shrimp performance.     

放养密度和微生态制剂对施氏鲟养殖水质的影响

将初始体质量(54.86±10.19)g的施氏鲟Acipenser schrenckii饲养在面积16m~2(4m×4m)、水深1.7~1.9m的陆基围隔中,密度分别为2 000尾/667m~2、3 000尾/667m~2、4 000尾/667m~2和5 000尾/667m~2,每个密度组均设3个平行,常规饲养,混合泼洒光合细菌、枯草芽孢杆菌和乳酸菌,第一次泼洒量为光合细菌50m L、枯草芽孢杆菌50g和乳酸菌50g,之后每5d泼洒第一次量的1/2,研究微生态制剂对静水土养殖池塘水质的影响。结果显示:水体中溶解氧量随养殖密度的增加逐渐降低(P0.05),氨氮、亚硝酸盐浓度随养殖密度的增加逐渐升高(P0.05)。在使用微孔增氧的条件下,泼洒微生态制剂对溶解氧量和氨氮浓度的影响不显著(P0.05),但显著降低了水体亚硝酸盐浓度(P0.05),显著增加了浮游动物生物量(P0.05)。     

Characterization of microbial communities in intensive GIFT tilapia (Oreochromis niloticus) pond systems during the peak period of breeding

Aquaculture pond is a complex ecosystem where the microorganisms in the sediments, in the animal intestinal tract and in water interact with each other to influence the water quality and health of aquatic animals. In order to understand the spatial distribution and relationship of microbial communities in intensively farmed genetically improved farmed tilapia (GIFT, Oreochromis niloticus), 454 high‐throughput pyrosequencing was applied to analyse the 16S rRNA gene of bacteria in intensive GIFT ponds in Wuxi City, Jiangsu Province, China. A total of 72 747 initial sequences were obtained from four depths of pond water, from tilapia large intestines and from pond sediment. The most common phylum in all samples was Proteobacteria, Actinobacteria and Cyanobacteria were the most abundant in water, Fusobacteria and Firmicutes in the large intestine and Chloroflexi in sediment samples. The sediment microbial community structure was comparatively similar to that of the tilapia large intestine. The microbial communities from different water depths were somewhat similar, especially the three most shallow samples, although the abundance of Actinobacteria gradually decreased with increased water depth. This data offer a preliminary exploration of the response mechanisms of the bacterial communities to aquafarming and contributes to the understanding of the status of bacterial communities of tilapia pond systems during the peak period of breeding from the aspect of their spatial distributions.     

Immunostimulatory effects of dietary poly‐β‐hydroxybutyrate in European sea bass postlarvae

The stable production of high‐quality fry in marine aquaculture is still hampered by unpredictable mortality caused by infectious diseases during larval rearing. Consequently, the development of new biocontrol agents is crucial for a viable aquaculture industry. The bacterial energy storage compound poly‐β‐hydroxybutyrate (PHB) has been shown to exhibit beneficial properties on aquatic organisms such as enhanced survival, growth, disease resistance and a controlling effect on the gastrointestinal microbiota. However, the effect of PHB on the developing immune system of fish larvae has so far not been investigated. In this study, the effect of feeding PHB‐enriched Artemia nauplii on survival, growth and immune response in European sea bass (Dicentrarchus labrax) postlarvae was examined. Amorphous PHB was administered to 28‐day‐old sea bass postlarvae over a period of 10 days. The survival and growth performance were monitored, and the expression of 29 genes involved in immunity, growth, metabolism and stress‐response was measured. While the expression of the insulin‐like growth factor 1 (igf1), an indicator of relative growth, was upregulated in response to feeding PHB, the larval survival and growth performance remained unaffected. After 10 days of PHB treatment, the expression of the antimicrobial peptides dicentracin (dic) and hepcidin (hep) as well as mhc class IIa and mhc class IIb was elevated in the PHB fed postlarvae. This indicates that PHB is capable of stimulating the immune system of fish early life stages, which may be the cause of the increased resistance to diseases and robustness observed in previous studies.     

封闭流水式网箱养殖混合供电系统设计

封闭流水式网箱养殖优点是零排放无污染,符合环保养殖要求,缺点是水质容易恶化,水交换与排污能耗大。为了降低能耗并确保设备正常运行,研发太阳能-市电-柴油发电机混合供电系统。基于蓄电池充放电特性,采用最大功率点跟踪(MPPT)和数字信号处理(DSP)技术实现太阳能智能充放电控制与保护,应用双电源自动转换开关技术实现有序混合供电。太阳能月均发电量250 k W·h,日均供电8.3 k W·h,满足负载日均耗电6.6~8.8 k W·h要求。结果表明,在阳光充足情况下,以太阳能供电为主;当出现连续阴雨天气情况下,供电顺序为蓄电池(充满状态可放电3~4 h)、市电、柴油发电机。随着太阳能系统性价比的提高,节能效果将更加明显。     

池塘养殖尾水经稻田生态工程净化后的浮游细菌群落特征

为利用稻田生态工程对精养池塘尾水进行循环利用,采用Illumina Mi Seq第二代测序技术比较分析了稻田生态工程进出水中浮游细菌群落结构和多样性差异,以探讨稻田生态工程净化回用水中浮游细菌群落变化对池塘养殖的影响。结果显示,稻田生态工程进出水中优势浮游细菌在门水平上的组成相同,均为蓝细菌门(Cyanobacteria)、变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、浮霉菌门(Planctomycetes)和拟杆菌门(Bacteroidetes)。但优势门类的相对丰度发生变化,蓝细菌门的相对丰度由进水中的46.72%显著降低至表面流出水中的41.82%和渗流出水中的34.77%;而放线菌门的相对丰度由3.90%增加至表面流出水中的5.65%和渗流出水中的6.45%。属水平上优势浮游细菌组成也相同,但微囊藻属(Microcystis)的相对丰度由0.83%显著降低至渗流出水中的0.46%(P0.05)。另外,稻田生态工程表面流出水中浮游细菌物种丰富度指数(Chao 1)显著提高,渗流出水中Shannon多样性指数显著提高,且Simpson指数显著降低(P0.05)。     

绍兴市凡纳滨对虾围垦滩涂养殖池塘的理化环境和浮游植物

2016年和2017年分别调查了位于浙江省绍兴市滨海新区的12口凡纳滨对虾围垦滩涂养殖池塘内的理化环境和浮游植物。结果显示:池塘内盐度变化范围为0~2,溶氧为6.2~13.9 mg/L,pH为7.5~9.8,总氨氮(TAN)为0.00~0.72 mg/L,亚硝酸盐氮(NO_2~--N)为0.00~1.70 mg/L,硝酸盐氮(NO_3~--N)为0.18~4.77 mg/L,总氮为1.74~6.08 mg/L,总磷为0.20~2.72 mg/L,总有机碳为1.88~42.57 mg/L,C/N为10~39。池塘内浮游植物种类隶属6门、24科、42属,其中蓝藻和绿藻为优势种。浮游植物生物量为(0.15~2.30)×107cell/L,叶绿素a(Chl.a)为2.62~37.24μg/L。Chl.a与蓝藻生物量显著正相关。NO_2~--N和NO3--N均与pH显著负相关。初步分析认为高pH可能是导致2016年池塘养殖凡纳滨对虾死亡率较高的重要原因,因此采取措施控制蓝藻生物量和水体的p H应有助于提高对虾养殖的存活率。     

Determination of selected antibiotics in farmed fish species using LC‐MS/MS

The aim of the study was to monitor the occurrence of 37 antibiotics from different classes including fluoroquinolone, tetracycline, macrolide, sulphonamide, penicillin, amphenicol and cephalosporin in three different farmed fish species (n = 75; rainbow trout, see bass, gilthead see bream) from five cities in Turkey. A method for LC‐MS/MS was optimized and validated to assess these antibiotics. As a result, 25 samples showed contamination with at least one antibiotic residue. The most detected antibiotics were norfloxacin (NOR) (18.7%), marbofloxacin (MAR) (12%), tetracycline (TC) (10.7), danofloxacin (DAN) (9.3%), oxytetracycline (OTC) (9.3%), tilmicosin (TLM) (8%) and enrofloxacin (ENR) (6.7%). A total of 17.3% of samples examined were found to be contaminated with residues exceeding the maximum residue limits (MRLs). The results indicate that antibiotics are frequently used in aquaculture production without the lack of knowledge. This study also revealed that the consumption of farmed fish could produce a public health concern as the level of residues for some antibiotics was much higher than MRLs.     

不同施肥条件对土池培育小球藻总脂含量及脂肪酸组成的影响

以辽宁盘锦光合蟹业有限公司养殖基地为试验场所,研究施以3种肥料(化肥、鸡肥、化肥与鸡肥的混和肥)对土池培育小球藻的主要营养指标——脂质含量和脂肪酸组成的影响。试验结果表明,施混合肥所培养的小球藻,其藻细胞密度略高于化肥组和鸡肥组;混合肥组小球藻的脂质含量(鲜质量的5.36%)也高于化肥组(鲜质量的4.02%)和鸡肥组(鲜质量的2.89%);混合肥组小球藻的多不饱和脂肪酸和高度不饱和脂肪酸的含量显著优于单一施化肥或鸡肥的小球藻。因此,在土池中施混合肥更有利于培育出高质量的小球藻。