Investigation of aquaculture dynamics at a Ramsar site,using earth observation systems in conjunction with a socio‐economic assessment

This study presents a comprehensive site‐scale analysis conducted within the global wetland inventory and mapping (GWIM) project. GWIM was developed and promoted by the International Water Management Institute (IWMI) through global partnerships to investigate wetland analyses at multiple scales. The present study investigates the complexity of an inland freshwater wetland system, presenting a conceptual framework for mapping and monitoring the dynamics of Lake Kolleru (a wetland of international importance, as defined by the Ramsar Convention), utilizing a geospatial platform. Illustrating the pace of land use changes leading to the progressive elimination of the wetland ecosystem of freshwater Lake Kolleru, this study also highlights the impacts of such changes on the socio‐economic system. A comprehensive temporal analysis (1977–2007) provided a structural base to schematically analyse the dynamics of biophysical and ecological changes to the wetland by effectively using a spectrum of remote sensing data. The present status and changing trends in ecological dimensions of Lake Kolleru were illustrated, utilizing information from spatial analyses, complimented with socio‐economic assessment. Attention is drawn to the potential of utilizing earth resources systems in exploring space–time interactions in freshwater ecosystems heavily modified through aquaculture interventions. Further, the spatial derivatives are meant as reference material for local authorities and decision‐makers to rehabilitate the economic livelihood activities to the social community dependent on the lake ecosystem. The disseminated message emphasizes the applicability of geospatial tools to enhance the efficacy of the decision‐making process by facilitating regular monitoring of ecosystem dynamics and providing updated information on wetland patterns and uses.     

The Effect of Ozonation on Particle Size Distribution for Recirculating Aquacultural Seawater: Analysis of Particle Flocculation and Breakup

ABSTRACT

Solids removal is very important for water quality maintenance in recirculating aquaculture systems (RAS). Ozonation is a practical water treatment which can promote the solids removal. However, the characteristics of ozonation effects on particles are still unclear. In this study, the effect of ozonation on particle size distribution (PSD) was investigated for seawater from a RAS of Pacific white shrimp (Litopenaeus Vannamei). Both flocculation and breakup of particles were demonstrated during ozonation treatment, which resulted in changes of PSD. By using a fractal characteristic value (D_f), the flocculation process could be divided into three stages of preparation, growth and steady. Besides, the flocculation efficiency varied parabolically with contact time. A higher ozone dosage resulted in a shorter preparation stage, along with a longer growth stage (namely lasting a longer flocculation effect) and thus a relatively higher limit of parabolic flocculation efficiency. However, the limit would reach a peak and probably be accompanied with a more breakup of particles. The best flocculation efficiency was 43% at ozone dosage of 3.5 mg/L with 5 min contact time. Furthermore, a higher ozone dosage could produce more ammonia.     

Dietary ascorbic acid and alpha-tocopherol mitigates oxidative stress induced by copper in the thornfish Terapon jarbua

The protective effects of vitamins C and E against oxidative stress were evaluated in various tissues of thornfish Terapon jarbua exposed to copper. Preliminary bioassay tests performed with copper and T. jarbua revealed that 4.0, 2.5 and 1.0 mg L(-1) of copper were lethal (LC(100)), medial lethal (LC(50)) and sublethal (LC(0)) respectively. Oxidative stress parameters viz. lipid peroxidation, superoxide dismutase, catalase, glutathione peroxidase, and glutathione were evaluated in control and experimental fishes. Lipid peroxidation activity increased in tissues of copper exposed fishes, while the antioxidant system exhibited a reduction in their activity. On the contrary copper stressed fishes fed with vitamins C and E enriched pellet feed showed significant reduction in lipid peroxidation activity and the antioxidant levels increased reaching near normal levels comparable to control values. Bioaccumulation of copper was studied in addition to oxidative stress. Substantial copper residue was detected in the tissues of T. jarbua exposed to copper and the level of copper in tissues reduced when the fishes were treated with vitamins ensuring copper depuration and thereby protecting them against stress. We concluded that vitamin supplementation offered significant reduction of the oxidative stress mediated by copper and we discuss the possible application of vitamins in costal aquaculture process.     

Utilisation of solar photovoltaic pumping for aeration systems in aquaculture ponds

This research pertains to solar photovoltaic (PV) pumping for aeration of aquaculture ponds and evaluates it economically. A stand-alone photovoltaic aeration system based on recycling of water at 10 cm under the water surface, at the surface (0 cm) and above the surface (30 cm) on a perforated tray was evaluated. The effect of pump discharges (35, 50, 65 L/min) on standard oxygen transfer rate (SOTR) and standard aeration efficiency (SAE) was investigated. Results revealed that the daily averages of PV energy output, PV efficiency and load energy were 0.844 kWh/d, 9.87% and 0.615 kWh/d, respectively, at 65 L/min and 42.7°C PV temperature. Water flow upward at 30 cm over the perforated tray in the radial direction proved to be better since it gave an opportunity for the exchange of gaseous between the water and the atmosphere. The SOTR and SAE for the third position were 0.025 kgO₂/h and 0.1 kgO₂/kW h, respectively.     

半滑舌鳎工厂化循环水养殖模式能值评价

为了更好地评价半滑舌鳎(Cynoglossus semilaevis Günther)在工厂化循化水养殖模式下的养殖效果及环境可持续性,运用能值理论及分析方法构建了半滑舌鳎循环水养殖模式能值流程图,并对此养殖模式各能值分布进行分析。结果表明:循环水养殖模式环境能值投入只占比1.08%,能值产出率(EYR)为2.433,环境负载率(ELR)为0.313 4,能值可持续发展指标(ESI)为7.763,表明此种养殖模式已经将农业生产提升至工业化水平,其经济系统发展程度高,生产效率较高;同时该养殖模式极大地减轻了对环境的压力,其可持续性和环境容纳量均较高。     

Natural decoloration,composition and increase in dietary fibre content of an edible marine algae,Ulva rigida (Chlorophyta), grown under different nitrogen conditions

The colour, dietary fibre content and characteristics of the edible marine green algae, Ulva rigida, were investigated in relation with the nitrogen content of the algal culture medium. Colour brightness decreased and total nitrogen of the algae increased in nitrogen-enriched conditions. When nitrogen-enriched seaweeds were grown again in normal seawater for 10 days, colour brightness increased and total nitrogen concentration fell. Total dietary fibre content of the wild and nitrogen enriched algae were close (～38.0% DW) but increased markedly when the nitrogen-rich plants were cultured in normal sea-water (54.4% after 10 days). Soluble fibre were xylorhamnoglucuronan sulphate (ulvan) with close molar compositions for all the seaweed samples. Insoluble polysaccharides were composed of glucose, xylose, uronic acid, rhamnose and sulphate which molar proportions varied for the different algal samples. The soluble fibre intrinsic viscosity and the water holding capacity of insoluble fibre were not markedly affected by the growth conditions. This report demonstrates that edible seaweed aquaculture provides an alternative or a complement to post-harvest transformations of seaweeds to modify organoleptic and nutritional characteristics.     

氧化塘/人工湿地工艺净化微污染养殖池水体

大量富营养物质沉积于池底,造成池塘老化,养殖环境劣化,严重危害健康养殖生产.采用氧化塘/人工湿地复合系统净化上海市崇明岛前卫村中心湖养殖池塘的微污染水体,氧化塘内的纤维填料采用人工方式挂膜,上面附着的大量黄褐色絮状污泥与纤维填料立体交织在一起,形成了无数张“网”,强化了微生物的种类和浓度,形成了藻菌共生体系;人工湿地内的陶粒基质比表面积大,易于微生物附着生长和吸附悬浮物.运行显示,该系统对COD、TN、TP、SS、叶绿素a的去除率分别为(38.3％～59.4％)、(20.5％～60.2％)、(43.9％～58.7％)、(66.7％～95.2％)、(15.7％～50.7％);净化效果呈现出季节性变化,夏季的净化效果最好.系统的最大处理水量可达441.5 m3/d,中心湖池塘的蓄水量约为7.0×104 m3,因而湖水的最小交换时间约为170 d.     

构建设施型精准化循环水养殖系统的技术研究

鉴于当前水资源短缺、环境恶化、水产养殖业高速发展,以及保障食品安全等问题的不断呈现,促使资源型工厂化流水养殖模式急需向高效型循环水养殖方向转变,这是产业发展提升的必然趋势。本文以工业化养殖理念为指导、节能减排为目标,以鲆鲽类产业技术体系构建的循环水养殖模式为样板,按循环水养殖系统(RAS)的设计原理,优化养殖工艺流程,构建一种设施型精准化的RAS,并初步分析探讨了海水鱼类在此集成系统中的应用效果。该系统将为广大水产养殖企业提供一种建设成本低廉、系统运行稳定可控、容易管理的实用新型养殖模式,也可为下一步发展现代水产精准养殖工程体系提供理论和实践依据。     

Production of Candida utilis biomass as aquaculture feed

Fish offal-peat compost was hydrolysed and the resultant liquid extracts used as substrate in the cultivation of the yeast Candida utilis. The yeast was able to grow in this culture medium, attaining a growth yield of approximately 260 g biomass kg^?1 total carbohydrate consumed. The biomass produced had a good amino acid composition, with a protein content of 520 g kg^?1, and a relatively low lipid content. Dry yeast was used as a feed component in the diet of cultivated rainbow trout (Oncorhynchus mykiss) in which it substituted well for other, traditional sources of protein.     

The effect of recirculating aquaculture systems on the concentrations of heavy metals in culture water and tissues of Nile tilapia Oreochromis niloticus

To date, farming fish in recirculating aquaculture systems (RAS) is one of the most environmentally friendly ways of producing fish. However, with the trend towards intensification, and consequently decrease in water exchange rates, these systems may accumulate substances, such as heavy metals, in the water and fish. Inductively-coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectroscope (ICP-MS) were used to determine Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn, in the water and fish (Nile tilapia Oreochromis niloticus). Three RAS were used, differing in daily water exchange rates (30, 70 and 1500 l/kg feed/d). The concentrations of As, Fe, Mn, Ni and Zn in the water increased with decreasing water exchange rates, suggesting an accumulation of heavy metals as more water was re-used. Such accumulation in the water was, however, not translated into accumulation in the liver and muscle. Accumulation of heavy metals was always higher in the liver than in the muscle; however, As reached 1.61 mg/kg wet weight in the muscle of fish farmed in RAS-70 l/kg feed/d. However, these levels are considerably lower than permissible safety levels for human consumption.