Effects of capital rationing and tax incentives on the internal growth of an aquacultural firm

Capital rationing and tax incentive issues for an aquacultural firm are developed in the context of intensive firm growth (growth from within rather than through acquisition) with a channel catfish enterprise. Beginning firm debt levels and stringently imposed debt limits (which the firm was not permitted to exceed) were found to have prominent effects upon pond construction levels and growth in profitability. Wide fluctuations in interest rate levels had little impact upon growth of the aquacultural enterprise, although higher interest rates significantly reduced profitability. The tax incentive examined also had little effect upon firm growth. The methodology developed and the effect of the capital, debt, interest rate level and tax features analyzed provide insights that may apply wherever capital and credit rationing impacts upon investment decisions by aquacultural firms.     

有机质对大型富营养化浅水湖泊沉积物磷吸附特征的影响

以大型浅水湖泊(太湖和巢湖)为研究对象,系统分析了沉积物有机质(OM)含量和组成、磷吸附参数、磷形态及间隙水溶解反应性磷(SRP)浓度在水平方向上的分布.吸附解吸平衡浓度(EPC0)与SRP浓度的比较结果表明,在太湖北部与巢湖南淝河入湖口等污染较严重的区域,沉积物仍表现出吸附磷的功能;OM与土壤有效磷(Olsen-P)、磷吸附指数和碱性磷酸酶活性均显著正相关,有机质分解所产生的小分子物质可增加磷的吸附容量;添加小分子有机质的室内模拟试验进一步证实了上述假设,糖类主要影响磷的吸附能,而氨基酸主要增加最大吸附量.有机质自身及其降解产物以不同方式影响沉积物对磷的吸附能力,并据此调节湖泊富营养化过程.     

莱州湾东部养殖水环境研究

通过对莱州湾东部海域的潮流数值模拟，详细地阐述了莱州湾东部海域的潮汐、潮流特征，特别对该海域的海水交换率与交换期进行了计算。结果表明，莱州湾东部秋季海水交换较夏季要快，而与其他海湾相比，莱州湾水交换能力较差。     

Effect of organic nitrogen and carbon mineralization on sediment organic matter accumulation in fish ponds

In aquaculture, ponds with high loads of organic inputs, organic matter accumulates at the bottom over time. Uneaten feed, senescent phytoplankton and faeces are the principal sources of accumulated material, but quantifications are scarce. The sedimented organic matter develops into a flocculent layer in which different processes transform the material into inorganic forms. A better understanding of factors influencing organic matter accumulation/decomposition in the sediment is needed to better understand and manage the dynamics of nitrogen in fish ponds. In this study, the rate of mineralization of organic nitrogen and the nitrogen flux between the sediment and the water column were measured. Organic matter accumulation in fish ponds was quantified, and the data were used to construct, calibrate and validate a dynamic simulation model of organic matter deposition/decomposition in fish ponds. The accumulating material consisted of dead phytoplankton, fish faeces and uneaten feed. Through model calibration, the proportion of these materials in the total accumulated organic matter was determined. In the model, gross photosynthetic rate was estimated from an empirical relationship with feed input. After calibration, the model was validated using independent data. The model simulated well the concentrations of organic carbon and nitrogen in the sediments but it may be developed further, especially by considering the effects of resuspension.     

超声技术降解养鱼污水有机物研究

设计一种超声系统试验装置进行超声工艺参数下的养鱼污水有机物降解性能试验和原水pH、溶解氧变化对养鱼污水有机物去除率影响试验;对试验前后养鱼污水有机物分子量分布特性一并展开讨论.结果表明,养鱼污水经频率20 kHz、声强0.1 W/cm2超声辐照3 min,COD去除率可达27.5%;对pH 5.5～8.5、溶解氧≥6.5 mg/L的养鱼污水,超声技术降解其有机物的性能不受影响;经超声辐照后的养鱼污水,其有机污染物质更易被曝气生物去除.     

岛礁海藻场沉积有机物来源辨析

海藻场的沉积有机物(sedimentary organic matter,SOM)是实现海藻场生态系统服务功能的重要物质基础,本实验以枸杞岛北部海藻场为研究区域,围绕大型海藻周年生活史的幼苗生长、成熟茂盛和衰退凋亡3个阶段,于2014年7月凋亡期、2014年10月生长期和2015年5月茂盛期对海藻场的SOM进行样品采集,并运用碳、氮稳定同位素技术,以C/N、δ~(13)C和δ~(15)N为指标分析了SOM的来源及变化。结果显示,1)7月、10月和翌年5月的SOM C/N的变化范围分别为5.9~6.6、6.0~6.9和5.4~6.2,可判定海藻场SOM是典型的海源性来源;2)7月不同水深的SOMδ~(13)C值空间变化明显,介于–20.3‰~–17.6‰,而10月和翌年5月都不显著,分别介于–22.3‰~–21.7‰和–21.4‰~–21.0‰;3)SOM的δ~(13)C值存在时间变化,而7月δ~(13)C值存在不同水深的空间变化;4)δ~(13)C、δ~(15)N和C/N之间的关系表明,7月SOM主要来源于浮游植物和大型海藻的混合贡献,而10月和翌年5月SOM则主要来源于浮游植物贡献;5)根据碳稳定同位素质量平衡混合模型计算得到,7月大型海藻对该海藻场SOM的平均贡献率最高可达53.71%;6)大型海藻产生的碎屑在SOM占比受波浪等海域动力环境影响显著。     

我国水产养殖工程学科发展报告（2007—2008）

报告概述了我国水产养殖工程学科2007-2008年所取得的重大科技成果和研究进展.重点介绍网箱设施工程、工厂化循环水养殖工程和池塘生态化养殖工程这3个领域开展的重大研究项目进展情况和研究结果,提出了该学科发展中存在的主要问题以及今后主要研究方向.     

基于nRF905的水产养殖环境参数自动监控系统

根据现代化水产养殖的低耗高效的发展要求,设计了基于nRF905的水产养殖环境参数自动监控系统.该系统把监控中心PC机作为上位机,通过VB 6.0构建上位机监控软件,同时以单片机MSP430作为下位机,并通过nRFg05构建无线传感网络,从而实现自动监控系统的各项功能.经过试验,该自动监控系统能够对DO、pH进行实时的数据采集、显示和存储,并与增氧机结合对DO进行自动控制以及超限报警.养殖现场试验结果表明,该系统工作稳定、实时性好、能耗低,控制电路设计简单、成本低,有一定的应用推广价值和实际意义.     

一体式膜生物反应器处理水产养殖废水膜污染特性研究

采用一体式膜生物反应器（ MBR）处理水产养殖废水,对处理过程中MBR膜污染的特征进行研究。首先,选取污泥浓度（ MLSS）、水力停留时间（ HRT）和曝气量这3个与膜污染有密切关系的变量,通过组合优化,研究操作条件对膜污染的影响,并确定最佳操作条件;其次,在最优化参数组合情况下,通过长期稳定运行,确定膜压增长特点;最后,通过膜阻力分布分析,得出造成膜污染的最主要原因。结果显示,对膜污染的贡献依次为：曝气量＞HRT＞MLSS;最佳的操作参数组合为曝气量437．5 L/h,HRT 4．25 h,MLSS 2．2 g/L;长期稳定运行过程中,发现膜压增长呈现出快速增长、平稳增长、急剧增长的3个阶段;通过膜阻力分布分析,得出由胞外聚合物（EPS）和微生物代谢产物（SMP）形成的吸附性膜孔阻塞是造成膜污染的最主要原因。因此,优化操作条件和减少混合液中EPS和SMP是减轻膜污染的重要手段。     

耐盐红螺菌对水产养殖病害细菌的拮抗作用

为探明光合理细菌对水产养殖动物病害的生物防治功能，对病鳖、鳗及南美白对虾动物体上的病原菌进行分离、纯化与鉴定，人工感染健康动物检测致病性；探讨耐盐红螺菌对病害细菌分离株的仰菌效能，和有效抑菌作用时细胞所处的生长期。试验结果表明，水产动物病害细菌分离株为孤菌属，气单胞菌属和假单胞菌属菌株；耐盐红螺菌的代谢产物对商害细菌分离株均有抑制作用，其平坂柳菌圈为1.2-1.4cm，最低抑菌浓度多为4-8倍稀释液；耐盐红螺菌的拮抗物质随细胞对数生长过程中生成，至细胞衰亡期达到最大值。     

四种渔药对稀有(鱼/句)鲫的急性毒性

用控温半静态换水式实验方法,测定了伊维菌素(0.4%)、辛硫磷(20%)、氯氰菊酯(4.5%)和精制马拉硫磷(20%)四种常用药物对稀有(鱼句)鲫(Gobiocypris rarus)幼鱼的急性毒性效应。分别在实验24、48、72 h和96 h后记录稀有(鱼句)鲫幼鱼的死亡数,并推算了实验药液的安全质量浓度。结果显示,四种渔药的96 h半致死浓度分别为7.01、24.22、9.37和460μg/L,安全浓度分别为0.70、2.42、0.94和46.00μg/L,这4种药物对稀有(鱼句)鲫的毒性大小依次为:伊维菌素>氯氰菊酯>辛硫磷>精制马拉硫磷。结果表明:稀有(鱼句)鲫可用于渔药对水体环境影响的监测。     

海水鱼类网箱养殖水域沉积物有机质的来源甄别

利用稳定碳氮同位素示踪技术,对南沙港网箱养殖水域沉积物中有机质的来源进行了分析研究。结果表明,网箱养殖区(距离网箱边缘100 m范围内)及对照区(距离网箱边缘大于500 m)沉积物的δ13C值分别为(-17.72±1.2)‰和(-12.73±0.38)‰,δ15N分别为(6.44±0.2)‰和(5.61±0.2)‰。网箱养殖区沉积物的有机质来源主要为残饵和鱼类粪便,比例分别占47.70%和27.71%。随着与养殖网箱距离的增加,网箱养殖源有机质(残饵和鱼类粪便之和)的比例降低,变化趋势符合指数方程y=97.167e-0.007 4x(R2=0.848 1),在潮流驱动的沉积物再悬浮及野生鱼类的扰动影响下,网箱养殖源有机质的水平位移可达400 m。鱼类网箱养殖的养殖废物是南沙港水域沉积物有机污染的主要来源。     

Analysis and optimisation of dynamic facility ventilation in recirculation aquacultural systems

Facility ventilation is one of the main energy consumers in a recirculation aquacultural system (RAS).In this work, operating points have been optimised in order to maintain an acceptable facility climate on the one hand but an energy input as low as possible on the other hand. The energy savings have been quantified by evaluation of energy input into the ventilation stream at various flow rates. Moreover, additional measurements have been undertaken in order to understand the correlation between air humidity in the facility, ventilation rate, humidity production of the RAS and ambient climate.The main findings are that dynamic facility ventilation offers a significant potential for energy savings up to 85% compared to a static operation at design flow rates according to DIN EN 13779. Air humidity–as a major constraint–is predominantly affected by ambient climate conditions. Based on the main findings, a first approach for a dynamic ventilation strategy (i.e. for automation) has been made.     

三沙湾养殖衍生有机物沉降对多毛类优势种营养生态特征的影响

为了解三沙湾网箱养殖活动的底栖生态环境效应,利用碳、氮稳定同位素(δ¹³C和δ¹⁵N)示踪结合数学模型方法分析区域内养殖衍生有机物(aquaculture-derived organic matter, AOM)沉降对5种底栖数量优势物种(多毛类的欧努菲虫Onuphis eremita、角海蛹Ophelina acuminata、索沙蚕属一种Lumbrineris sp.、丝异须虫Heteromastus filiformis和不倒翁虫Sternaspis scutata)营养生态特征的影响。结果表明,AOM (包括残饵和粪便)、颗粒有机物和底栖微藻是三沙湾底栖优势物种的潜在食源,各类食源δ¹³C和δ¹⁵N均有显著差异(Kruskal-Wallis检验,P<0.001)。底栖优势物种的营养级存在显著差异(Kruskal-Wallis检验,P<0.001),杂食性索沙蚕属一种和欧努菲虫营养级最高,两者分别为2.79和2.78;底泥食性丝异须虫、角海蛹和不倒翁虫分别为2.62、2.41和1....     

Effect of organic matter concentration on agricultural limestone dissolution in laboratory soil–water systems

Laboratory soil – water systems in which soil organic matter was increased by 0.0%, 0.5%, 1.0%, 2.0% and 4.0% by adding dry, chopped ryegrass (Lolium perenne) shoots to sandy soil containing 0.06% organic matter. Agricultural limestone was added to the systems, and pH, alkalinity and hardness of the water were monitored for 65 days. The pH, alkalinity and hardness increased with greater soil organic matter concentration. Amounts of carbon dioxide released by microbial respiration increased at the higher soil organic matter concentrations, and this resulted in more rapid and greater solubility of agricultural limestone. The results suggest that greater soil organic matter concentrations in ponds favour the rate and extent of agricultural limestone dissolution.     

高效液相色谱法检测海水养殖环境中喹诺酮类药物残留

建立了一种养殖海水中诺氟沙星、环丙沙星和恩诺沙星3种喹诺酮类抗生素残留量的高效液相色谱-荧光测定方法。水样经稀盐酸调pH后经HLB固相萃取柱富集、净化,用外标法定量。结果表明,诺氟沙星、环丙沙星和恩诺沙星检出限分别是2、1和1μg/L,定量限分别是6.6、3.3和3.3μg/L,添加浓度为10、20和50μg/L时,3种物质的回收率为71.9%～85.3%,批内变异系数≤10%,批间变异系数≤7%。利用该方法对黄海沿岸部分养殖场及近岸海水(北起36°40.303′N,121°8.939′E;南至35°39.36′N,119°52.433′E)进行分析,诺氟沙星、环丙沙星、恩诺沙星的检出质量浓度分别为6.20～982、55.2和11.6～55.4μg/L。实验结果表明,该方法灵敏度高,重现性好,适用于养殖海水中诺氟沙星、环丙沙星和恩诺沙星的检测。     

Studies in circulated fish ponds: organic matter recycling and nitrogen transformation

Abstract. Three types of circulated systems slocked with tilapia were studied: tanks: miniponds; and ponds. Water was continually circulated and aerated. Daily drainage of non-suspended material was applied in most systems. The continual circulation and resulting resuspension of the organic particular ma Her led to a very high rate of microbial activity. Organic carbon was efficiently metabolized and utilized in the food chain. Inorganic nitrogen was completely oxidized and accumulated in water as nitrates, unlike conventional ponds. The establish men! of an active nitrifying population took, however, a period of about 3 weeks during which high levels of ammonium and nitrite were built up. The water body was continually aerated, yet local anaerobic conditions developed, especially in non-drained tanks or in miniponds where the plastic bottom was covered by a soil layer. Such conditions led to a less efficient organic carbon metabolism, to reduced nitrification and to denitrifcation. Fish growth seemed to be retarded in systems where denitrifcation took place, indicating that the growth-retarding factor is associated with production of anaerobic metabolites in the pond. The role of daily drainage and a proper aeration system is to avoid formation of anaerobic pockets.     

Seasonal fluctuations in the flux of particulate organic matter discharged from net pens for fish farming

ABSTRACT:   Fish farming using net pens consumes large amounts of food for the reared fish, resulting in organic enrichment of the sediment below the fish farm from organic discharge in the forms of fish feces and food residues. Sediment traps were set at a net pen within and outside a fish farm, and organic flux on the sea floor was compared. The year-mean organic flux to the sea floor caused by fish farming from September 2003 to September 2004 was estimated at 2.11 gC/m²/day in total organic carbon (TOC) and 0.26 gN/m²/day in total nitrogen (TN), which were 2.5 times (TOC flux) and 2.2 times (TN flux) larger than that for natural organic flux outside the fish farm. The seasonal fluctuation patterns of organic flux to the sea floor below the fish farm did not necessarily coincide with those for the amount of food spent for the fish farming. The largest organic flux to the sea floor occurred in the autumn, when the vertical mixing of the water had just started. Therefore, organic enrichment of the sediment on the sea floor of a fish farm proceeded during this season.