罗非鱼活性肽分离及抗氧化能力研究

利用正交试验L9(34),以清除超氧自由基能力为指标,分别对木瓜蛋白酶、中性蛋白酶水解罗非鱼肉的水解条件进行优化,并对最佳清除率下的两种酶解物进行Sephadex G-50凝胶柱分离,检测了各组分对超氧自由基清除率及活性肽分子量分布情况.结果表明:中性蛋白酶在45 ℃、酶的质量分数2.0%、水解105 min及肉水比1∶3的水解条件下对超氧自由基有较好清除作用;木瓜蛋白酶在60 ℃、酶的质量分数2.0%、时间150 min及肉水比1∶2的水解条件下对超氧自由基有较好清除效果.木瓜蛋白酶酶解物在分子量为660 Da的多肽洗脱峰具有最大超氧自由基清除率,中性蛋白酶酶产物在分子量为1320 Da多肽洗脱峰具有最大超氧自由基清除率.     

氯嘧磺隆在大豆植株和土壤中的残留动态研究

为了制定氯嘧磺隆在大豆上的安全使用标准,将50%氯嘧磺隆可湿性粉剂于大豆生长期进行茎叶喷雾处理,用高效液相色谱法,研究了氯嘧磺隆在大豆植株及土壤中的残留动态,测定了氯嘧磺隆在大豆及土壤中的残留量.两年的试验结果表明,氯嘧磺隆在大豆植株中比在土壤中消解得快,其半衰期分别8.77～8.86 h和10.47～11.07 d.大豆收获期籽粒中最终残留量低于0.005 mg/kg,土壤中最终残留量低于0.003 mg/kg.     

稻粉虱Aleurocybotusindicus的研究

本文描述了稻粉虱的形态特征，研究了稻粉虱的为害习性、生物学特性、生活史、世代历期、种群动态、寄主、越冬和防治方法．结果表明，稻粉虱在福州地区１ａ发生８代，第３、４、５代是为害水稻的主害代，应用扑虱灵防治稻粉虱，防治效果达到９０％以上     

Application of system dynamics approach for time varying water balance in aerobic paddy fields

Increasing water scarcity has necessitated the development of irrigated rice systems that require less water than the traditional flooded rice. The cultivation of aerobic rice is an effort to save water in response to growing worldwide water scarcity with the pressure to reduce water use and increase water productivity. An accurate estimation of different water balance components at the aerobic rice fields is essential to achieve effective use of limited water supplies. Some field water balance components, such as percolation, capillary rise and evapotranspiration, can not be easily measured; therefore a soil water balance model is required to develop and to test water management strategies. This paper presents results of a study to quantify time varying water balance under a critical soil water tension based irrigation criteria for the cultivation of non-ponded “aerobic rice” fields along the lower parts of the Yellow River. Based on the analysis and integration of existing field information on the hydrologic processes in an aerobic rice field, this paper outlines the general components of the water balance using a conceptual model approach. The time varying water balance is then analyzed using the feedback relations among the hydrologic processes in a commercial dynamic modeling environment, Vensim. The model simulates various water balance components such as actual evapotranspiration, deep percolation, surface runoff, and capillary rise in the aerobic rice field on a daily basis. The model parameters are validated with the observed experimental field data from the Huibei Irrigation Experiment Station, Kaifeng, China. The validated model is used to analyze irrigation application soil water tension trigger under wet, dry and average climate conditions using daily time steps. The scenario analysis show that to conserve scarce water resources during the average climate years the irrigation scheduling criteria can be set as −30 kPa average root zone soil water tension; whereas it can be set at −70 kPa during the dry years, however, the associated yields may reduce. Compared with the flooded lowland rice and other upland crops, with these two alternatives irrigation event triggers, aerobic rice cultivation can lead to significant water savings.     

Interacting effects of yak dung deposition and litter quality on litter mass loss and nitrogen dynamics in Tibetan alpine grassland

The effects of grazing‐induced dung deposition on plant growth and soil attributes are well established, but little is known about dung effects on litter decomposition. Here, we tested effects of yak dung on litter decomposition and nutrient content in a Tibetan alpine meadow. We incubated litter of four common alpine meadow species using litter bags in the field. Two low‐quality species (Kobresia capillifolia and Elymus nutans) with low nitrogen (N), high C/N and Lignin/N, and two high‐quality species, (Saussurea nigrescens and Thermopsis lanceolata) were incubated in monoculture with and without dung addition. Mass loss of leaf litter, fibre fraction (cellulose, hemi‐cellulose and lignin), N and phosphorus (P) were measured after 6, 12 and 18 months of incubation in the field. Dung addition significantly increased decomposition constants for low‐quality litter species, but not for high‐quality litter species. Dung addition promoted cellulose and hemi‐cellulose loss, but lignin loss was not affected by dung addition, except after 12 months for high‐quality litter species. Dung reduced N immobilization after 6 months and did not affect subsequent release in low‐quality litter species, and promoted N release after 6 and 12 months in high‐quality litter species. Regardless of litter quality, dung increased P release after 6 and 12 months. Our results suggest grazing‐induced dung deposition may accelerate C and nutrient turnover, primarily through increasing the mass loss of low‐quality litter, P release from litter and N release from high‐quality litter. The mechanisms underlying the effects of dung deposition need to be clarified in future studies.     

The behavioural dynamics of fishers: management implications

In pursuing their livelihood, fishers develop strategies when faced with changes in regulations and other fishery conditions. Changes involve each individual in a decision‐making process governed by his/her own goals or constraints. Despite this reality, the complex dynamics of fishing has usually been ignored in designing management initiatives, which has contributed to management failures in many parts of the world. Fishers have generally been treated as fixed elements, with no consideration of individual attitudes based on their operating scales (geographical, ecological, social and economic) and personal goals. We review existing research on the social, economic and behavioural dynamics of fishing to provide insight into fisher behaviour and its implications for fisheries management. Emphasis is placed on fisher perception, and how fishers develop dynamic fishing tactics and strategies as an adaptive response to changes in resource abundance, environmental conditions and market or regulatory constraints. We conclude that knowledge of these dynamics is essential for effective management, and we discuss how such information can be collected, analysed and integrated into fisheries assessment and management. Particular emphasis is placed on small‐scale fisheries, but some examples from industrial fleets are provided to highlight similar issues in different types of fisheries.     

凡纳滨对虾高位池养殖水体细菌变动及其与理化因子的关系

自2008年4月至8月,在广东省汕尾市红海湾凡纳滨对虾（Litopenaeus vannamei）高位池养殖基地全程采集养殖池塘水样,检测水体细菌类群和理化因子,分析养殖过程中细菌类群的数量变化规律及其与环境因子的关系。结果显示,养殖过程中水体异养细菌、弧菌（Vibrio）和芽孢杆菌（Bacillus）的数量波动性较大,其中异养细菌波动范围1.35×10^4～1.39×10^6cfu·mL^-1,平均4.73×10^5cfu·mL^-1;弧菌波动范围1.05×10^3～5.20×10^4cfu·mL^-1,平均1.80×10^4cfu·mL^-1;芽孢杆菌波动范围0.11×10^3～4.30×10^3cfu·mL^-1,平均6.6×10^2cfu·mL^-1;粪大肠菌群（fecalcoliform）大多在1.0×10^2cfu·L^-1以内,平均0.97×10^2cfu·L^-1,远低于无公害食品海水养殖用水水质标准。对细菌与理化因子的单因子分析显示,异养细菌与溶解氧（DO）呈显著的负相关性（P〈0.05）,弧菌与pH呈极显著的负相关性（P〈0.01）,与化学需氧量（COD）和总磷（TP）呈显著的正相关性（P〈0.05）。多因子偏相关分析显示,异养细菌和弧菌与DO、pH、COD、TP的相关关系均不显著（P〉0.05）。结果表明,调查的养殖池塘对虾生长良好,该养殖池塘是安全、基本健康的系统,水环境中细菌数量受养殖系统中生物、环境因子及人为因素的影响和制约。     

Infection dynamics of Neoheterobothrium hirame (Monogenea) on juvenile olive flounder, Paralichthys olivaceus (Temminck & Schlegel), in coastal waters of Japan

A recent epidemic of the invasive monogenean Neoheterobothrium hirame is suspected to have caused the significant decline of the commercial catch of olive flounder, Paralichthys olivaceus, in Japan. To clarify the causal link between parasite invasion and host depletion, we monitored the infections of N. hirame on juvenile flounder for 2 years at two widely separate bays, Obama Bay, experiencing a devastating reduction in flounder catches, and Miyako Bay with a stable catch. Prevalence, mean intensity and abundance of developmental stages of N. hirame were compared between the bays and between fish year classes. Fishes captured at Obama Bay harboured three times more worms than those at Miyako Bay and had a significantly higher overall prevalence of infection. In addition, there was a negative correlation between parasite intensity and host condition factor at Obama Bay, suggesting a causal link between the N. hirame epidemic and the reduction of local flounder populations.     

Vertical Distribution and Seasonal Dynamics of Fine Root Parameters for Apple Trees of Different Ages on the Loess Plateau of China

The vertical distribution pattern and seasonal dynamics of fine root parameters for the apple trees of different ages （3, 10, 15, and 20 years old） on the Loess Plateau of China were studied. Soil coring method was used to determine the vertical distribution and seasonal dynamics of fine roots at different root radial distances （1.0, 1.5, and 2.0 m from the main tree trunk）. The fine root biomass density （FRD）, fine root length density （RLD）, and specific root length （SRL）, as well as soil water content and soil temperature were also measured. The FRD and RLD for the 10, 15, and 20 years old trees reached peak values in the 20-30 cm soil layer. For the 3 years old tree, the highest FRD and RLD were observed in the 10-20 cm soil layer. The FRD and RLD decreased with increased soil depth from the 10-20 or 20-30 cm soil layer for all age apple trees. The SRL declined with the increase of tree age. The FRD at the 1.0 m radial distance from the main tree trunk was higher than that at other radial distances in the 3 and 10 years old orchard. However, in the 15 and 20 years old orchards, especially the 20 years old orchard, the FRD at the 2.0 m radial distance was nearly equal to or higher than that at the 1.0 and 1.5 m radial distances. For all the root radiuses or the tree ages, the FRD, RLD, and SRL were the highest in spring and the lowest in autumn. The age of an apple tree does not affect the vertical distribution pattern but the biomass of fine roots and the SRL. Radial distance affects the root horizontal distribution of 3 and 10 years old trees but the 15 and 20 years old trees. Additionally, effects of soil temperature and soil moisture on fine root distribution or seasonal dynamics are not significant.