Microbial dynamics in RAS water: Effects of adding acetate as a biodegradable carbon-source

This study evaluated the effect of an abrupt increase in easily biodegradable carbon (acetate) on bacterial activity and abundance in the water of recirculating aquaculture systems (RAS). The study included a batch experiment with RAS water only, and an experiment at system level where twelve pilot scale RAS were used. The batch experiment was made to test how acetate concentration would influence the microbial state in RAS water. Further, we wanted to observe if the selected microbial analysis tools would be able to detect these changes. The second experiment was carried out in twelve identical and independent RAS that had been operated under constant loading conditions (1.6 kg/m³ make-up water) for five months prior to the trial. The twelve RAS were divided into four treatment groups in triplicates: i) control with submerged biofilter (Ctrl + bf); ii) control without submerged biofilter (Ctrl-bf); iii) acetate addition in RAS with submerged biofilter (Ac + bf); and iv) acetate addition in RAS without submerged biofilter (Ac-bf). The biofilter media from the groups without submerged biofilter (Ac-bf and Ctrl-bf) was removed just 5 h prior to the start of the trial. The two acetate treatment groups (Ac + bf and Ac-bf) were spiked with 40 mg/L of acetate three consecutive times (0, 24 and 48 h). Consumption of acetate, bacterial abundance and bacterial activity were followed for 72 h after the first acetate spike for both experiments. Bacterial activity was quantified by BactiQuant^® and hydrogen peroxide (HP) degradation assay. Bacterial abundance was assessed by quantifying micro-particles and free-living bacteria. In the batch experiment we observed a significant increase in bacterial activity proportional to the amount of acetate added, and a corresponding significant increase in microparticles (1–3 μm). In the pilot scale RAS experiment, the acetate addition in RAS with submerged biofilter did not cause an increase in bacterial activity, or in the number of microparticles in the water phase but a significant increase in bacterial activity and number of microparticles were observed in the RAS without submerged biofilter (Ac-bf). These changes were particularly pronounced shortly after each acetate spike.In RAS with submerged biofilters, the acetate was presumably consumed primarily by the bacterial community within the biofilm, and consequently, only minor changes were observed in densities of free-living bacteria in the water phase. The results of the study suggest that heterotrophic bacteria in the submerged biofilter have a high capacity to handle fluctuation of organic matter loading in RAS, thereby stabilizing the abundance and activity of bacteria in the water column.     

噬菌蛭弧菌应用研究进展

噬菌蛭弧菌(Bdellovibrio)是寄生于其他细菌并能导致其裂解的一类革兰氏阴性细菌。它对人、动物和植物的绝大多数致病菌具有裂解作用。该文就蛭弧菌在水产养殖、家禽养殖及其他方面的潜在应用以及目前存在的主要问题进行了综述。     

芦笋常见病虫害及其综合防治技术

针对芦笋各种常见病害的发病症状、发病原因以及常见虫害的危害特点,提出综合防治技术.     

稻鸭共生技术对水体生态环境的影响研究

调查了大面积实施稻鸭共生技术地区的稻田表面水和周围流域河水以及水生生物相。结果表明:稻鸭共生田的表面水的EC、COD、T-N等值与传统栽培田水质相比普遍增高,稻鸭共生期间稻田排水易导致水质污染,为了防止周边水质的污染,需要彻底做好水的管理工作。     

Preliminary Nutritional Analysis of Lancelets,a Promising Seafood with Aquacultural Potential

Abstract

Lancelets are filter feeding, fish-like, marine chordates that resemble anchovies. Although they are widely distributed in coastal areas of the U.S.A., especially in the Southeast, and have been used as a food source in other countries, the only nutritional analysis of lancelets was performed in 1941 on preserved specimens. We report nutritional data on freshly processed lancelets, including a proximate analysis, fatty acid profile, and amino acid profile. These data are preliminary because of the limited number of samples and time periods of collection, but they are important because no similar data exist for this potential food resource. Moisture composed 88.9% of the sample, protein 9.4%, ash 1.3%, and fat 0.7%. Carbohydrates, as estimated by subtraction from the total, are absent. Cholesterol was only 18.3 mg per 100 g sample. Omega-3 fatty acids composed 30% of total fatty acids or 0.58 g per 100 g sample of whole lancelets. The fatty acid profile reveals some similarities to that of vertebrate fishes as well as to invertebrate shellfish, but also reflects the unique nature of lancelets. An uncommon omega-3 fatty acid, 22:5, is prevalent in the lancelet profile in addition to 22:6 and 20:5. The fatty acid data also suggest that the diet of lancelets is diverse, consisting of phytoplankton and zooplankton. The amino acid profile, with glutamic acid, aspartic acid, and glycine as the most common residues, reflects the preponderance of muscle and collagen and the absence of cartilage and bone.     

Shellfish aquaculture in Thailand

Abstract

Shellfish have been farmed in Thailand for over 100 years, and during this time, traditional culture techniques have gradually given way to more sophisticated and capital intensive methods. Farmed shellfish production increased from 73,976 to 138,202 metric tonnes between 1988 and 2000. Major species currently under cultivation include the green mussel Perna viridis, the blood cockle Anadara granosa, and three species of oyster (Saccostrea cucullata, Crassostrea belcheri, and Crassostrea iredalei). The horse mussel Arcuatula arcuatula is also produced in limited amounts for animal feed, and gastropods such as the abalone Haliotis asinina and the spotted babylon Babylonia areolata are in the initial phases of commercialization. With the globalization of fisheries commodity markets, the Thai shellfish sector is slowly implementing more rigorous management and certification processes. These procedures are required to access European, American and Japanese markets, and would also serve to decrease the risk of gastrointestinal disease for local consumers.     

Largemouth bass predators reduce growth,feeding and movement in juvenile channel catfish

Fine ML, Mayo MS, Newton SH, Sismour EN. Largemouth bass predators reduce growth, feeding and movement in juvenile channel catfish. Ecology of Freshwater Fish 2011: 20: 114–119. © 2010 John Wiley & Sons A/S Abstract – Animals utilise sensory cues to make decisions that will decrease their vulnerability to predation. With a well‐developed olfactory system and taste buds located inside the mouth and on the external body surface, catfishes are excellent subjects to investigate nonconsumptive predator effects. Juvenile channel catfish Ictalurus punctatus are often eaten by largemouth bass Micropterus salmoides, and we tested the hypothesis that largemouth bass fed catfish would adversely affect foraging and growth in channel catfish. Groups of catfish were placed in tanks partitioned by a mesh screen: experimental tanks had a largemouth bass on the other half of the tank, and control tanks had an empty chamber. Experimental catfish exhibited a long‐term decrease in spontaneous motion, feeding and growth. Feeding catfish to the bass caused the experimental catfish to freeze after a multi‐second latency suggesting transport of an alarm cue. Thus, there were long‐term effects from the continuous presence of the bass and additional short‐term cues from the bass consuming a catfish.     

制约中国水产业经济发展方式转变的因素及对策——以青岛市为例

改革开放以来中国水产业发展取得了巨大成就，近几年各主产区也在积极转换发展方式，取得了一定成效，但目前水产业还没有摆脱依靠生产规模扩张和大量消耗自然资源为主的粗放型经营方式。本研究以青岛市为例分析了制约水产业经济发展方式转变的因素，提出了体制创新、科技创新、提高劳动者素质等加快水产业经济发展方式转变的对策。     

浅谈市政道路管线综合设计

市政道路管线的特点;市政道路管线综合的平面、纵断面及管线交叉设计;合理控制各管线的管距、标高.     

银川市宁华园、燕鸽糊基地居住区绿化效果的调查与分析

在银川市宁华园、燕鸽湖基地两个小区绿化状况调查的基础上，对绿化材料种类、空间布局、视觉效果、生长效果、绿化效果等进行分析，并总结绝对化经验。