Modelling current speed and carrying capacity in long-line blue mussel (Mytilus edulis) farms

The development of the mussel (Mytilus edulis) farming industry in Norway is based on suspended long‐line culture, and large areas of the coast are potentially suitable for farming. Norwegian fjords and coastal waters are regarded as oligotrophic environments in comparison with sites where most studies on mussel feeding on natural seston have been carried out. High mussel culture densities in oligotrophic water may cause seston depletion, resulting in low growth or tissue wasting due to reduced feeding and negative net energy balance. In this paper we present a carrying capacity model based on rate conditional processes, balanced against flushing and with emphasis on flow reduction as a function of farm design. The model is based on assumptions that friction forces are a function of geometric shape of the channel made up by the suspended mussel ropes as vertical boundaries and it quantifies carrying capacity according to information of farm length, space between long lines, seston concentration and background current speed and the relative importance of these factors. Estimates of how stocking density in mussel farming can be optimized in relation to the food supply (i.e. carrying capacity) are crucial to production management decisions, and the model may provide predictors for decisions regarding new site selection or expansion of existing operations.     

乳山对虾养殖场白斑综合征病毒(WSSV)调查研究

2002年采用PCR-核酸探针斑点杂交法检测了乳山对虾养殖场1000余份样品携带白斑综合征病毒(WSSV)的情况。结果显示,639例对虾样品中阳性检出率为26·6%;77例蟹类样品中阳性检出率为18·2%;266例浮游动物样品中阳性检出率为38·3%,3~9月份浮游动物阳性率呈下降趋势,消毒后水体中浮游动物的阳性率仍很高;30例贝类样品检测均为阴性;204例底泥样品中,阳性检出率为17·6%,22例抽滤海水样品检测均为阴性。结果表明,虾、蟹类在传播WSSV中起着重要作用,贝类、海水传播WSSV的可能性很小,浮游动物、底泥在传播WSSV中的作用和机制应引起高度重视。     

Cage culture of sutchi catfish, Pangasius sutchi (Fowler 1937): effects of stocking density on growth, survival, yield and farm profitability

The sutchi catfish, Pangasius sutchi (Fowler 1937) was grown at 10 stocking densities in cages suspended in a river‐fed channel during the summer of 2000. Catfish fingerlings (mean length 9.1–9.7 cm and mean weight 5.9–6.7 g) were stocked at densities of 60, 70, 80, 90, 100, 110, 120, 130, 140 and 150 fish m^?3. After 150 days, growth and yield parameters were studied and a simple economic analysis was carried out to calculate profitability. The mean gross yield ranged from 15.6±0.27 to 34.5±0.44 kg m^?3 and the net yield ranged from 15.2±0.22 to 33.5±0.36 kg m^?3 and showed significant variations (P<0.05). The mean weights of fish at harvest were inversely related to stocking density. Both gross and net yields were significantly different and were directly influenced by stocking density but the specific growth rate, survival rate and feed conversion rate were unaffected. Higher stocking density resulted in higher yield per unit of production cost and lower cost per unit of yield. The net revenue increased positively with increasing stocking density. A density of 150 fish m^?3 produced the best production and farm economics among the densities tested in this experiment.     

华东某省部分禽场重金属污染检测与分析

对华东某省部分家禽养殖场的水体、饲料及其粪便重金属含量进行了调查。共采集包括水样、饲料及粪样在内的49份样品,其中水样16份,饲料样24份,粪样9份。样品经微波消解处理,用原子吸收法测定了铜(Cu)、锌(Zn)、铅(Pb)、镉(Cd)、铬(Cr)含量,用电感耦合等离子质谱法测定砷(As)、汞(Hg)含量。结果表明:水样中各元素含量均符合地表水环境质量标准中三类水质要求;部分饲料样品中铬和砷含量超过饲料卫生标准要求,超标率分别为33.3%和8.3%,其中铬元素最高含量达622.5mg/kg,砷元素含量最高为5.8mg/kg;粪样中除铜元素超标外,其余元素均在标准范围内。研究提示少数家禽养殖场存在一定的重金属污染,应加强对其饲料中铜、砷、铬的含量控制。     

2013年安徽省中小规模种猪场猪伪狂犬病群流行率及风险因素横断面研究

[目的]了解安徽省中等规模种猪场猪伪狂犬病病毒（PRV）的感染情况。[方法]2013年8月至11月,开展了中等规模种猪场猪伪狂犬病群流行率和风险因素的横断面研究。通过简单随机抽样方法,选取了380个中等规模种猪场;用发现疫病的抽样策略,在每个种猪场采集了5份母猪血清,使用IDEXX公司猪伪狂犬病病毒gE-ELISA试剂盒进行了抗体检测。同时开展了问卷调查,并对种猪场之间PR传播潜在的29个风险因素进行了统计学分析。[结果]2013年安徽省中等规模种猪场猪伪狂犬病的群流行率为34.1%（95%置信区间29.3%~38.9%）;没有灭鼠措施（OR=2.5,95%置信区间：1.4~3.7,P<0.001）、购入种猪未经检测（OR=2.2,95%置信区间：1.1~4.2,P=0.024）、未免疫含PR 6种以上猪病（OR=2.0,95%置信区间：1.2~3.1, P=0.004）是2013年安徽省中小规模种猪场感染PRV的风险因素。Logistic 回归拟合度较好（P>0.05）,ROC曲线下面积为0.68（95%置信区间：0.62-0.73）。[结论]安徽省中等规模种猪场场间PR流行率较高,建议购入种猪前需进行检测,免疫含PR等6种以上猪病疫苗并定期灭鼠。     

樟木头林场森林可持续经营研究

从指导思想、经营方针与目标等方面论述了樟木头林场森林可持续经营的总体思路,划分了9种森林经营类型,对每一类型确定了具体的森林经营技术措施;制定了林场的生物多样性保护与生态安全规划,提出了森林可持续经营的保障措施,实施以提高森林生产力和稳定性、保护森林生态系统生物多样性为重点的森林可持续经营。     

海陵湾网箱养殖区浮游植物群落结构及其与环境因子的关系

为研究海陵湾鱼类网箱养殖对浮游植物群落的影响,于2019年1月、4月和11月对海陵湾上、中、下游三个网箱养殖区进行了冬、春、秋3个季度的浮游植物及主要水质因子的调查。共检出浮游植物3门39属96种(含变种),其中硅藻门29属76种、甲藻门8属16种、蓝藻门2属4种。浮游植物细胞丰度范围为0.00022~3.05×105cell/L,秋季>春季>冬季,湾口处丰度在秋冬两季远大于湾内。冬季优势种主要为细弱海链藻（Thalassiosira subtilis）和佛氏海毛藻（Thalassiothrix frauenfeldii）,春季优势种为细弱海链藻（T. subtilis）和中肋骨条藻（Skeletonema costatum）,秋季优势种主要为中肋骨条藻（S. costatum）和佛氏海毛藻（T. frauenfeldii）。冬、春、秋季各采样站多样性指数范围分别为1.44~4.11、0.66~2.39和1.62~3.10。冗余分析表明,冬季盐度、pH,春季氨氮、pH,秋季硝酸盐、溶解氧对浮游植物优势种影响显著。受河流径流和养殖活动的影响,海陵湾相邻采样站间的浮游植物群落相似性在秋季最高、冬季次之、春季最低。浮游植物群落的相似性差异与调查站位间环境的区域性差异关系密切。     

培肥后的黑土肥力变化研究

本实验结果表明,黑龙江省黑土施用农家肥后,土壤有机质、全氮量分别增加0.19～0.55％,0.02～0.07％,速效磷增加0.41～19.75毫克/100克土;复合胶体的数量也相应提高,增值复合量为0.16～1.04％;土壤物理性质得到改善。农家肥的应用,增强了土壤肥力的后劲。     

新乡市污灌区蔬菜地重金属污染状况调查分析

通过对12份土壤样品中Pb、Cd、Cr、Ni、Zn含量的测定,分析了河南省新乡市污灌区蔬菜地土壤重金属污染状况,结果表明,Pb含量在45.08～245.26mg/kg,Cd含量在0.54～25.60mg/kg,Cr含量在11.21～90.16mg/kg,Ni含量在33.88～90.12mg/kg,Zn含量在342.32～663.06mg/kg。分别以河南省土壤背景值和国家环境质量二级标准为评价标准,计算出各采样点的土壤重金属污染指数,结果表明,以河南省土壤背景值为评价标准,各采样点普遍受到了不同程度的重金属污染,甚至表现为重度污染;而以国家环境质量二级标准评价,蔬菜地主要受到来自Cd、Ni、Zn的污染。     

湖南休闲农业现状及人才需求研究

湖南作为农业大省,休闲农业资源丰富且初具规模。在这样的趋势下,休闲农业人才的需求将出现"井喷"态势。分析了湖南休闲农业与休闲农庄的现状,对湖南休闲农庄人力资源现状及人才需求进行了调研和分析,提出了加强休闲农庄管理、扩大休闲农庄融资渠道、建立校企合作机制、构建科学人才培养模式及共享专业资源平台等相关建议。