鳄龟养殖焦点谈

鳄龟（American Snapping Turtle）别名小鳄龟、肉龟，原产于美国。国内自1997年后少量引进饲养。养殖发现：鳄龟生长速度明显快于国内乌龟品种，且出肉率高，适应性强，养殖极具效益。一经媒体宣传报道，众多水产养殖场纷纷引进苗种。由于鳄龟苗种供应几乎完全依赖进口，国内庞大的需求量和美国供应数量的有限，造成龟苗价格扶摇直上，从1997年的每只75元人民币一路涨至130元人民币，且价格多年坚挺。近两年来随着国内部分种龟开始繁殖，龟苗数量逐年增加，价格呈现理性回归的态势，并且龟苗产销两旺。如今鳄龟养殖也逐渐成为乌龟养殖业中一道亮丽的风景线。鳄龟快速养殖试验多次见于报端。本文就鳄龟养殖的一些现象谈谈自己的一些初浅见解，起到抛砖引玉的作用。     

佛州拟鳄龟龟蛋孵化方法

<正>为保证佛州拟鳄龟种质基因的纯正,促进佛州拟鳄龟养殖业的良好发展,从2014年起,我们承担了本市的"佛州拟鳄龟引种选育及良种推广"科技项目,与养殖场合作进行佛州拟鳄龟的引种及繁育技术研究等工作。龟蛋的孵化,是项目技术研究中的关键点之一。龟蛋的人工孵化一般有控温孵化、自然常温孵化两种     

鳄龟的养殖技术

鳄龟，又名肉龟、美国鳄龟和蛇鳄龟，原产于中美洲和北美洲。鳄龟有两个品种，即大鳄龟和小鳄龟，大鳄龟体重可达100kg以上，性凶猛会伤人，不宜养殖。鳄龟通常指的是小鳄龟，一般体重（5～10）kg，性较温和，不主动伤人。鳄龟具有三大特点：①生长速度奇快，自然温度下年增重高达1kg左右，半控温养殖（气温18℃以下时加温），年增重（1．5-2）kg，最高记录年增重2．5kg，其生长速度是世界上其它龟、鳖类品种无法比拟的。②耐寒、耐高温、食性杂、少病害，对环境适应能力强，在我国所有省份自然状态及控温条件下都能养殖。尤其可贵的是，鳄龟对水量要求不多，北方地区养殖无须担心水源不足。③集食用、药用和观赏于一身。     

鳄龟高密度养殖技术研究

鳄龟是我国近年来从美国引进的优良龟种之一，分大鳄龟和小鳄龟两个品种，小鳄龟又分黄背和黑背两个种群。我们研究的品种为小鳄龟，主要研究其高密度养殖新技术，对黄背和黑背不做分别研究。高密度养殖技术研究目的主要是寻找一种适合我国实际的低投入高产出的效益型养龟新方法、新技术、新工艺。     

山东省攻克鳄龟人工繁育难关

由济南市淡水科研所担纲的鳄龟北方人工繁育课题取得突破性进展,健康鳄龟幼苗繁育成功,这标志着我国北方地区鳄龟人工饲养进入新的阶段,人工饲养鳄龟靠南方引苗的局面将被打破。经过近一年的漫长研究和等待,该市淡水科研所技术人员一举突破了鳄龟北方地区繁育难题。7只活蹦乱跳的小鳄龟幼仔于近日在该市淡水科研所养殖车间破壳而出,体长平均在2cm～3cm。据科研所研究人员介绍,为解决鳄龟产卵,他们制作了产卵池,以沙土覆盖,与亲龟生活的水池相隔一个通道。鳄龟进入产卵期后,亲龟每天夜晚陆续离开水池,爬进沙土池产卵。研究人员每天都要对产卵…     

蛇鳄龟(肉龟)的人工养殖技术

<正> 蛇鳄龟又名鳄龟、肉龟、小鳄龟(相对大鳄龟而言),因其肉多体壮而著称于世。蛇鳄龟近年引入我国,由于控温养殖年净增重可达1000—1500克,出肉率高达85％—90％,营养丰富等特点而被众多特种水产养殖者看好,笔者经2年的人工养殖,取得了一些经验,现就养殖技术介绍如下:     

鳄龟的室内——池塘两段养殖法

<正> 鳄龟又称肉龟、小鳄龟、蛇鳄龟等,以其出肉率最高(85%—89%)而闻名于世。自从美洲引进后经几年的试养实践,因集观赏、食用、滋补、药用多种功能于一体而走俏海内     

鳄龟周年生态养殖技术

<正> 鳄龟又称小鳄龟(以别于大鳄龟)、蛇鳄龟等,因其出肉率高达85%—89%,又称肉龟而闻名于世。自从美洲引进经过6年试养证实,因集观赏、食用、滋补和药用等多种功能于一体而走俏海内外,每公斤售价达800元还有价无货。     

“六条禁令”再树渔政新形象

前不久,从山东省传来喜讯,由济南市淡水科研所承担的鳄龟北方人工养殖课题取得突破性进展,成功繁育出鳄龟幼苗,这预示着我国北方地区鳄龟人工饲养将有可能进入新的阶段,人工饲养鳄龟靠从南方进苗的局面将被打破。经过近一年耐心的研究和等待,该所技术人员一举突破了鳄龟北方地区繁育难题。7只活蹦乱跳的小鳄龟幼仔于近日在该所养殖车间破壳而出,体长在(2～3)cm。据研究人员介绍,为帮助鳄龟顺利产卵,他们制作了产卵池,以沙土覆盖,与亲龟生活的水池相隔一个通道。鳄龟进入产卵期后,亲龟每天夜晚陆续离开水池,爬进沙土池产卵。研究人员每天都要…     

鳄龟品种分大小 孵化条件不一样——兼答读者问

<正> 笔者近日收到不少读者来信,反映读了贵刊10期介绍的《肉龟养殖技术》不尽全面,与我场介绍的文章内容也不尽一致。现借贵刊一角,就读者朋友关心的问题答复如下: 品种:被誉为肉龟的鳄龟原产美国和加拿大,其纬度相当于我国和俄罗斯,在3—45℃水温中均能生活。分为小鳄龟和大鳄龟两个品种,近几年引进我国。贵刊10期文章介     

On the Use of Price Ratio in Aggregate Supply Response: Some Evidence from the Poultry Industry

The specification of supply/demand relationships has received considerable attention in agricultural economics (Heien 1977). Economic theory has helped provide a basis for the specification of such relationships, one of its contributions being the proposition that prices should be interpreted only in relative terms. This has had a profound influence on model building in agricultural economics, leading a number of researchers to avoid the use of absolute prices in economic analysis. For this reason, numerous market models of the agricultural economy use price ratios as explanatory variables (e.g., Chen; Chen et al.; Heien, 1976; Gerra; Kulshreshtha and Wilson; Rahn; Talpaz; Morzuck et al.; Houck and Gallagher; Wilson et al.); these examples suggest that the use of such ratios is fairly widespread in econometric modeling of the crop and livestock sectors. One of the best examples of price ratios is the "feed cost to price" ratio commonly used in the analysis of livestock supply response. Indeed, since feed cost constitutes a major part of the total production cost in livestock activities, the "feed cost to price" ratio is often considered a proxy for profitability. For this reason, data on such ratios are regularly published for various livestock activities (e.g., USD A). Also, "feed cost to price" ratios are often employed in the specification of models of livestock supply response, (e.g., Chen; Chen et al.; Heien 1976; Gerra; Kulshreshtha and Wilson; Rahn; Talpaz). However, not all models of aggregate supply response follow this approach. For example, Freebairn and Rausser, and Arzac and Wilkinson, use prices as separate variables rather than in ratio forms in their models. In particular, they do not employ price ratios in their livestock and crop supply equations. The existence of these different approaches raises questions about the appropriateness of the use of price ratios in the modeling of aggregate supply.     

RELATIVE PRICE VARIABILITY AMONG AGRICULTURAL COMMODITIES AND MACROECONOMIC INSTABILITY IN THE UNITED KINGDOM

This paper develops measures of relative price variability among agricultural commodities in the UK farm sector for the period 1956-88. Econometric tests of the hypothesis that relative price variability is positively correlated with instability in the macroeconomy are carried out. The results indicate that UK agricultural commodity prices become more volatile relative to one another when the economy-wide inflation rate increases and when aggregate output becomes more variable. These findings suggest that UK producers and consumers of domestically grown farm products experience increased risk and uncertainty in their production and consumption decisions during periods of macroeconomic instability. The effects of UK entry into the European Community are also examined; no evidence is found to suggest that adoption of the Common Agricultural Policy reduced year-to-year relative price variability among agricultural commodities.     

Structural Breaks and the Relationship between Barley and Wheat Futures Prices on the London International Financial Futures Exchange

Co-movement between futures prices can arise when commodities are substitutes. Counterintuitively, Dawson and White fail to find a significant long-run link between feed barley and wheat prices on the London International Financial Futures Exchange. This relationship is re-examined using  Johansen, Mosconi, and Nielsen's co-integration procedure that permits structural breaks. Results show evidence of co-integration and hence price discovery. There is a significant break in October 2000 following Common Agricultural Policy intervention price reductions, the barley–wheat futures market is perfectly integrated, and the barley price Granger-causes the wheat price. Modeling structural breaks in price relationships appears important.     

A household hedonic model of rice traits: economic values from farmers in West Africa

New crop varieties often have been promoted in developing countries based upon superior yield vis-a-vis locally available varieties. This research presents a hedonic price model for upland rice by drawing upon the input characteristics and consumer good characteristics model literature. Model specification tests determine that a combination of production and consumption characteristics best explains the willingness to pay for new upland rice varieties. The household model specification determined that five traits explain the willingness to pay for new rice varieties: plant cycle length, plant height, grain colour, elongation/ swelling and tenderness. Yield was not a significant explanatory variable of the willingness to pay for seed. The implications of this model are two-fold. First, varietal development and promotion must include post-harvest characteristics in addition to production traits when determining which varieties to promote for official release. Secondly, non-yield production characteristics such as plant height and cycle length are significant factors in producer's assessments of the value of a new variety. Overall, this paper provides an alternative explanation for limited adoption of modern upland rice varieties in West Africa: varietal evaluation programs have focused too narrowly on yield evaluation and have not promoted varieties with superior non-yield characteristics than locally available varieties.     

Farm-gate tomato price negotiations under asymmetric information

This article provides an empirical analysis of farm‐gate tomato price negotiations under asymmetric information. Regression models are estimated to analyze when and by how much sellers stick to their initial ask prices and what explains the variation in the initial ask–offer price spread. Detailed information on 66 farm‐gate tomato transactions and daily tomato wholesale price data from the central vegetable market in Addis Ababa are used for the analysis. Estimation results show that farmers are less committed to their initial ask price when the buyer speaks out the transaction price first, when their quality perceptions of the tomatoes being transacted differ from those of the buyers, and when their tomato farm is at a large distance from the main road. Sellers stick more to their initial ask price when they know that the central market price is high. The initial ask–offer price spread decreases when the buyer speaks out the initial negotiation price first, but increases in the difference in quality perception between buyer and seller, and in the quantity of tomatoes being transacted.     

关于我国粮食安全保护问题的几点思考

尽管我国粮食实现了8年连续增产,但是,从外部环境、市场供求价格、进出口贸易方面分析,粮食安全问题仍然不可掉以轻心。据此,必须合理上调粮食价格,让利益趋动粮食生产持续发展;正确看待土地规模经营与流转,大力推进粮食生产服务外包,让地尽其力,从源头上解决粮食安全问题;从宏观整体的高度协调好政策环境、资源供给、市场管理、区域经济发展、对外贸易各种关系,确保国家粮食长期、稳定、持续安全。     

AGRICULTURAL TRADE AND MCA's: A SPATIAL EQUILIBRIUM ANALYSIS

The purpose of this paper is to demonstrate how some aspects of agrimonetary system of the Common Agricultural Policy may be analysed using spatial equilibrium diagrams, modified to include foreign exchange sectors. The model analyses the effects of monetary compensatory amounts on intra-Community trade. The results are: first, when the intervention price is below the market price, both the importing and the exporting country gain in social welfare; and second, when the intervention price is effective, only the importing country gains. In each case the cost of the MCA's exceeds these welfare gains. From a budgetary viewpoint there is a trade-off between the cost of intervention buying and the cost of the trade subsidy.     

On the Comovement of Commodity Prices

We present strong evidence against the excess-comovement hypothesis—that the prices of commodities move together beyond what can be explained by fundamentals. Prior studies employ broad macroeconomic indicators to explain common price movements, and potentially correlated fundamentals are not controlled for. We use inventory and harvest data to fit a partial equilibrium model that more effectively captures the variation in individual prices. The model explains the majority of the comovements among commodities with high price correlation, and all of the comovements among those with marginal price correlation. Common movements in supply factors appear to play an important role in the observed comovements in commodity prices.     

A MODEL OF THE COMMON AGRICULTURAL POLICY

Several efforts have been made since 1980 to estimate the costs and benefits of the European Community's Common Agricultural Policy (CAP). This paper summarises the approach and method adopted in developing one such effort, which aims to provide results at country, commodity and interest group level both for the CAP as a whole, and for changes in it. Economic analysis of the effects of price changes in the CAP is carried out with the use of direct and crossprice elasticities of supply and demand for sixteen major commodities, using base levels of production, consumption, and gross trade flows in each member state, along with rest-of-world data. A number of CAP instruments, such as subsidies, levies, quotas and ‘green’ exchange rates, are built into the calculations and can be varied, along with support prices, to produce new situations in domestic markets and in world price levels. Both financial (budgetary) and welfare (economic surplus) effects of such exogenous price changes can be calculated. Certain policy changes, such as a move to ‘free’ markets, involve endogenous calculation of equilibrium prices. Trend projections subject to a priori constraints are used to produce results for years beyond the extent of data currently available. The types of model run commonly carried out are discussed, along with several strategic judgments that became necessary in carrying out the research. Finally, questions concerning the future development and use of the model are addressed.     

SIMULTANEITY IN THE UK DAIRY SECTOR*

Because of the high degree of interdependence in the livestock sector, the endogenous variables of econometric models should be simultaneously determined. This paper describes the specification, estimation and evaluation of a model of the UK dairy sector in which the herd size, number of culls, replacement heifer price and milk price are determined simultaneously. The major policy conclusion that emerges from the model is that any attempt to increase the price of milk received by farmers via a structural change in the policy rule used to fix the price will be offset by over 50% as a result of increases in the supply of milk.