两种经验方法估算中国明对虾自然死亡的比较

为掌握不同自然死亡估算方法对资源变动规律和群体结构特征的影响,以放流中国明对虾渔业为例,采用2种基于生长参数的经验公式估算自然死亡系数,并与已报道的基于渔获量数据得到的结果进行比较,分析3种自然死亡系数随时间的变化规律及对资源的性比结构影响。结果显示:估算方法理论及依据的数据资料不同对自然死亡系数的估算结果影响显著,利用叶昌臣等基于渔获量数据得到的自然死亡系数进行放流后至捕捞结束全时段的模拟,存在低估放流初期个体自然死亡的现象;利用Chen等提出的经验公式估算的自然死亡系数,存在高估放流初期幼体自然死亡的可能,至放流个体生长一周年时性比达4.44:1;利用Gislason等提出的方法估算的自然死亡系数,存在低估放流初期和高估稳定生长期自然死亡的可能,至放流个体生长一周年时性比达2.22:1。在开捕时的BPR和捕捞结束时的累计YPR,基于叶昌臣等估算的自然死亡系数得到的值分别为23.81和22.02,分别是利用Gislason等经验公式得到的值的2.42倍和2.87倍,是利用Chen等提出方法得到的资源量的76.25倍和102.50倍。研究表明,选择渔业资源自然死亡估算方法应以最谨慎的方法进行审查和对比,利用经验方法进行自然死亡系数估算时,为提高估算的准确性、科学性和得到结果具有生物学意义,应引入性别因子(或系数)。     

北京农产品地理标志认知的实证分析

基于消费者对北京农产品地理标志认知情况的实际调查,分析消费者对北京农产品地理标志的认知现状及原因。研究表明,北京农产品地理标志存在认知相对较低、宣传力度不够和品质独特性较低等问题,提出提升北京农产品地理标志认知水平的政策建议。     

应用模糊聚类评价布氏田鼠为害等级

由于各地环境条件和布氏田鼠密度与种群分布格局的差异,其为害程度很难用统一的数量化指标加以评价,造成了准确测报该鼠为害水平的困难。本文试采用模糊聚类的方法,结合该鼠数量、分布格局以及多项环境因子的定性、定量指标加以综合分析,依其聚类结果可进行该鼠为害等级的全面评价,根据作者收集的20组数据的微机处理,表明这种方法可进行大区域不同环境条件下的为害等级评价,具有良好的应用前景。     

Comparison of methods to assess dog owners' therapeutic compliance

Objective To compare different methods for assessing the compliance of veterinary clients administering medication to their dogs.
Procedure Thirty-one owners whose dogs were prescribed amoxycillin-clavulanate, twice and thrice daily, for a duration of five to seven days were recruited from three Sydney veterinary hospitals. Compliance was assessed by electronic monitoring devices, return medication counts, client self-reports and veterinarians' estimation of likely compliance.
Results Electronic monitoring showed owners administered on average 84% (range 7 to 104%) of prescribed medication to their dogs. Both return medication counts and client self-reports tended to overestimate therapeutic compliance when compared with electronic monitoring. When questioned, the majority of owners (71%) claimed perfect compliance with the prescribed regimen. No correlation was found between veterinarians' estimates of owner compliance and that assessed electronically.
Conclusion Electronic monitoring provided valuable information on dose timing and variation, but proved costly and difficult to employ in veterinary practice. Simplicity and low cost of return medication counts makes this method attractive for use in veterinary compliance studies. Client self-reports reliably detected some noncompliers and permitted identification of individual problems or errors. For practical purposes a combination of return medication counts and client self-reports may have merit in future veterinary compliance studies.     

Testing genetic determinism in rate of hoof growth in pigs using Bayes Factors

Excessive growth and consequent deformity of hooves is a frequent disorder in some purebred pig populations. A test to detect possible genetic determinism related with this phenomenon was performed using the Bayes Factor (BF). Data were available for females from three purebred selection lines: Landrace (561 records), Pietrain (183) and Large White (225). Animals were scored in four categories, according to the overall growth rate of their hooves. A Bayesian analysis was performed separately for each line using a threshold model with a probit approach, and Bayes Factors between models with and without additive genetic effects were computed. Results from the three lines showed that models exhibiting genetic variability were much more probable than those that did not include a genetic component, with BF values of 312, 35 and 40 (and posterior probabilities of 0.99, 0.97 and 0.98), respectively, for the Landrace, Pietrain and Large White lines. Monte Carlo estimates of posterior means of heritabilities were medium to high (0.25, 0.41 and 0.38, respectively), and the highest posterior density region for heritability at 99% did not include zero in any of the three lines. These results allow us to conclude that genetic determinism has an important influence upon the rate of hoof growth in the pig. A potential genetic response can be achieved in the populations analysed, but further studies are needed to determine the genetic architecture of hoof growth disorders in pigs.     

Estimation of the carcass composition from a cross-section of the rib-loin from crossbred Japanese Black × Limousin F2 cattle by computer image analysis

The carcass composition of crossbred Japanese Black × Limousin F2 cattle was examined in order to find an accurate carcass composition equation. The test animals included 17 steers and 17 heifers. The 28 image measurements from the area encircling the vertical line to the thoracic vertebra and the line from the thoracic vertebra between the sixth and seventh rib‐bones were measured by computer image analysis. The relationships between the 29 parameters that added the carcass left side weight of the animal and the carcass composition were suggested. The carcass composition included muscle weight, muscle ratio, fat weight and fat ratio. The carcass composition from steers was estimated by an equation composed of these three or four parameters (R² = 90.80%, 79.30%, 90.75% and 73.70%, respectively). The selected parameters were measured without cutting the thoracic vertebra. The carcass composition from heifers was estimated by an equation composed of two to four parameters (R² = 96.15%, 90.98%, 93.60% and 88.22%, respectively). The parameters for the estimation of the muscle and fat weight, and muscle and fat ratio are very similar. Furthermore, the equations using the parameters could estimate the carcass composition from the Japanese Black × Limousin cattle resource population.     

Factors Associated with Grassland Bird Species Richness: The Relative Roles of Grassland Area, Landscape Structure, and Prey

The factors responsible for widespread declines of grassland birds in the United States are not well understood. This study, conducted in the short-grass prairie of eastern Wyoming, was designed to investigate the relationship between variation in habitat amount, landscape heterogeneity, prey resources, and spatial variation in grassland bird species richness. We estimated bird richness over a 5-year period (1994–1998) from 29 Breeding Bird Survey locations. Estimated bird richness was modeled as a function of landscape structure surrounding survey routes using satellite-based imagery (1996) and grasshopper density and richness, a potentially important prey of grassland birds. Model specification progressed from simple to complex explanations for spatial variation in bird richness. An information-theoretic approach was used to rank and select candidate models. Our best model included measurements of habitat amount, habitat arrangement, landscape matrix, and prey diversity. Grassland bird richness was positively associated with grassland habitat; was negatively associated with habitat dispersion; positively associated with edge habitats; negatively associated with landscape matrix attributes that may restrict movement of grassland bird; and positively related to grasshopper richness. Collectively, 62% of the spatial variation in grassland bird richness was accounted for by the model (adj-R² = 0.514). These results suggest that the distribution of grassland bird species is influenced by a complex mixture of factors that include habitat area affects, landscape pattern and composition, and the availability of prey.     

Density estimates of rural dog populations and an assessment of marking methods during a rabies vaccination campaign in the Philippines

We estimated the population density of dogs by distance sampling and assessed the potential utility of two marking methods for capture-mark-recapture applications following a mass canine rabies-vaccination campaign in Sorsogon Province, the Republic of the Philippines. Thirty villages selected to assess vaccine coverage and for dog surveys were visited 1 to 11 days after the vaccinating team. Measurements of the distance of dogs or groups of dogs from transect lines were obtained in 1088 instances (N = 1278 dogs; mean group SIZE = 1.2). Various functions modelling the probability of detection were fitted to a truncated distribution of distances of dogs from transect lines. A hazard rate model provided the best fit and an overall estimate of dog-population density of 468/km² (95% confidence interval, 359 to 611). At vaccination, most dogs were marked with either a paint stick or a black plastic collar. Overall, 34.8% of 2167 and 28.5% of 2115 dogs could be accurately identified as wearing a collar or showing a paint mark; 49.1% of the dogs had either mark. Increasing time interval between vaccination-team visit and dog survey and increasing distance from transect line were inversely associated with the probability of observing a paint mark. Probability of observing a collar was positively associated with increasing estimated density of the dog population in a given village and with animals not associated with a house. The data indicate that distance sampling is a relatively simple and adaptable method for estimating dog-population density and is not prone to problems associated with meeting some model assumptions inherent to mark-recapture estimators.     

家蚕产卵量的基因效应参数估计

用产卵量差异较大的两个近交系782和Ekp作亲本,配制了F1、F2正反交及F1与两亲本的回交B1和B2,加上两亲本P1和P2共8个世代,采用多世代平均值的多元回归分析方法对产卵量的基因效应参数进行了估计,得到了如下结果：（1）建立了分析家蚕产卵量的常染色体基因加性、显性和性染色体基因加性效应的非二体遗传模型,并通过实际数据检验表明产卵量遗传符合这个模式;（2）产卵量的遗传主要取决于常染色体上基因加性效应,其次是性染色体基因加性效应,显性效应很小。     

广东省大学生运动休闲消费特征研究

为提高潜水蒸发计算精度，利用潜水蒸发强度、埋深为零时的土面蒸发强度和水面蒸发强度的实测资料对阿维里扬诺夫公式、叶水庭公式和雷志栋公式中E₀值的选取进行了探讨，同时对比分析了E₀分别为水面蒸发强度和埋深为零时土面蒸发强度两种情况下的潜水蒸发强度。结果表明，针对新疆地区粘壤土类型，对于上述三种公式，若用埋深为零的土面蒸发强度代替水面蒸发强度，计算结果会产生误差，精度偏低，应选用E₀为水面蒸发强度进行计算，获得了η与地下水埋深的指数函数关系。该研究为潜水蒸发经验模型中E₀值的选取提供参考，同时为求解雷志栋公式中参数η提供一种新方法。