反相高效液相色谱法测定瘤胃液中的生物胺

本文旨在应用反相高效液相色谱法建立瘤胃液中生物胺的测定方法.样品经0.5 mol/L盐酸提取后,用丹磺酰氯柱前衍生,流动相为乙腈和0.1 mol/L乙酸铵溶液;采用梯度洗脱,流速为1.0 mL/min;紫外检测器波长254 nm,柱温30℃.应用该方法,研究高精料和低精料饲粮条件下瘤胃液中5种生物胺浓度的差异.结果表明...     

建筑数值风洞的基础研究

数值风洞模拟要想获得理想的计算精度,依赖计算人员的理论基础及其在具体操作中对各种重要因素的选择.针对这个问题,本文采用一个CUBE建筑模型的风洞试验的试验结果作为比较标准,比较了各种不同条件下的建筑数值风洞模拟结果和试验结果,着重分析了网格划分、计算区域、湍流模型和对流项的差分格式等因素对建筑数值风洞数值模拟结果的影响.模拟结果表明:在各种影响因素中,计算区域的影响相对较小,而网格划分、湍流模型的影响相对较大.最后给出如何对上述各种因素作出合理选择的建议.     

空蚀、磨损及其联合作用研究进展

空蚀、磨损及两者联合作用是目前流体机械破坏的重要原因，通过实验及数值模拟研究得到空蚀、磨损及两者联合作用的机理是发展流体机械优化设计方法、提高流体机械抵抗空蚀磨损破坏能力的基础．由于影响空蚀、磨损及两者联合作用行为的因素既有速度、压力等流场参数，又有沙粒和材料特性等，近年来此领域的研究在空蚀磨损及联合作用机理、各因素间的相互影响及高抗破坏材料等方面展开．基于此，本文选择性的分析了相关的报道文献，为进一步开展流体机械过流表面快速破坏机理的研究提供理论支持．     

流体播种技术发展及其关键技术分析

干旱缺水是影响旱作农业的重要因素,研究旱作节水技术是保证国民经济正常发展和农业可持续发展的前提和基础.流体播种是一种抗旱、节水、增产的新技术.为此,在调查和试验研究的基础上介绍了流体播种技术及其在节水,提高出苗率、成活率等方面的特点;简述了保水剂的发展和应用情况以及流体播种机具的研究现状;分析了影响流体播种技术应用的排种器伤种、流体播种液的配制、播种精度和均匀度、保水剂的使用经济性等关键技术问题,并探讨了其解决措施,可为流体播种技术和播种机具的研究提供参考.     

Physiological and biochemical parameters for egg quality determination in lake trout,Salmo trutta lacustris

The present study investigated the relationships between egg viability and ovarian fluid composition, egg physiology and egg metabolism in lake trout, Salmo trutta lacustris, to obtain biomarkers for egg quality determination. The ovarian fluid pH, protein levels and activities of aspartate aminotransferase and -d-glucuronidase were significantly correlated with egg viability expressed as the number of eyed stage embryos. Regression models demonstrated that an ovarian fluid pH between 8.44 and 8.57, protein levels below 235.56 mg 100 ml^–1ovarian fluid, aspartate aminotransferase activity below 31.65 m min^–1 l^–1ovarian fluid and -d-glucuronidase activity below 8.62 m min^–1 l^–1 ovarian fluid characterized egg batches with high viability (80%).The increase in the egg wet weight during water hardening was also significantly correlated with the number of eyed stage embryos, and egg batches with high egg viability (80%) increased in wet weight by 13% during water hardening.From the investigated metabolic parameters the number of eyed stage embryos was significantly correlated with activities of NADP-dependent isocitrate dehydrogenase (egg viability 80% at 2.07 nM min^–1 mg^–1 protein) and NAD-dependent malate dehydrogenase (egg viability 80% at 47.25 nM min^–1 mg^–1 protein), with the respiration rate (egg viability 80% at 8.71 nM min^–1 mg^–1 protein), with the ratio of NADH to NAD levels (egg viability 80% 0.872), with the levels of free, non-esterified fatty acids (egg viability 80% 72.34 g mg^–1 protein), and the ratio of non esterified to esterified fatty acids (egg viability 80% at 0.749). Also, subjective and visual control methods were described to distinguish between batches with viable and non viable eggs.     

Assessing opportunity and relocation costs of marine protected areas using a behavioural model of longline fleet dynamics

Increasing use of spatial management tools in fisheries requires an understanding of fleet response, and in particular to where displaced fishing effort is likely to move. We develop a state‐dependent decision‐making model to address the spatial allocation of effort in an Australian tuna longline fishery. We assume that fishers have an economic objective in deciding where to fish, but that decisions in any period are also influenced by the remaining quota held at the time of the decision. Key features of the model include endogenous price dynamics, a moving stock and a competitive pool of different vessel types operating from different port locations. We utilize this model to illustrate fleet responses to marine reserves and limits on fishing effort. The results illustrate that the model framework provides advantages over statistically based models in that decisions made in response to the imposition of a reserve are not consistent with a proportional reallocation of effort. Rather, the stochastic dynamic model yielded an overall profit level of ～4% higher relative to scenarios with no reserve. Incorporating the opportunity cost of a quota into the model resulted in an optimal utilization of effort, in which effort was concentrated in time periods and locations yielding maximized profit. Under a low level of effort relative to the season length, the model indicated an overall profit level 43% greater than the highest obtained when the same level of effort was applied solely within any given quarter of the season.     

Sex steroids in the seminal fluid and milt quality indices in the endangered Caspian brown trout,Salmo trutta caspius

In this study, the relationships between the seminal fluid sex steroids sperm quality parameters (i.e. sperm motility and sperm production were investigated in the endangered Caspian brown trout. According to results, the variation of sex steroid concentrations was comparatively high. The seminal fluid levels of 17α‐Hydroxyprogesterone (OHP) had positive correlation with percentage and duration of sperm motility. Similar correlation was found between the seminal fluid concentration of testosterone (T) and estradiol‐17β (E2) with sperm concentration. As well as, there was no significant correlation between progesterone (P) with sperm quality indices. The significant correlation of some steroids i.e. OHP, T and E2 and sperm quality parameters of Caspian brown trout confirms the key role of these steroids in acquisition of the potential of motility during final stage of the maturation.     

Linking habitat selection, emigration and population dynamics of freshwater fishes: a synthesis of ideas and approaches

Abstract –  The consequences of individual behaviour to dynamics of populations has been a critical question in fish ecology, but linking the two has proven difficult. A modification of Sale's habitat selection model provides a conceptual linkage for relating resource availability and individual habitat selection to exploratory behaviour, emigration and population-level responses. Whole-population experiments with pupfish Cyprinodon macularius that linked all factors along this resource to population continuum lend support to this conceptual model, and illustrate that emigration may be much more common in fish populations than considered in most individual- or population-based models. Accommodating emigration can enhance the ecological appropriateness of behavioural experiments and increase confidence in extrapolation of experimental observations to population-level effects. New experimental designs and advancing technologies offer avenues for assessing population consequences of habitat selection and emigration by individual fish. Emigration often is the key linkage between individual behaviour and population responses, and greater understanding of the underlying factors affecting this often-overlooked demographic parameter could offer new approaches for management and conservation of fishes.     

Is it possible to differentiate between environmental and fishery effects on abundance‐biomass variation? A case study of blackspot seabream (Pagellus bogaraveo) in the Strait of Gibraltar

We assessed the potential for simulation and modelling of the blackspot seabream (Pagellus bogaraveo) population in the Strait of Gibraltar to discriminate the environmental effects of fishery impacts. A discrete biomass–abundance dynamic model was implemented to obtain a simulated monthly time series of blackspot seabream biomass. On this simulated time series, autoregressive integrated moving average (ARIMA) models were fitted. The best ARIMA fit provided a significant correlation of 0.76 and persistence index higher than 0.85. The proportion of variance non‐explained by the ARIMA models was correlated with a time series of sea surface temperature (SST) and North Atlantic Oscillation (NAO). The analysis of global, annual and winter correlation between the proportion of variance not explained by the ARIMA models and environmental variables showed that significant associations were not detected over the full time series. Our analysis therefore suggests that overexploitation is the main factor responsible for the commercial depletion of blackspot seabream in the Strait of Gibraltar.     

Motility Parameters of Rainbow Trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>) Spermatozoa in Relation to Sequential Collection of Milt,Time of <Emphasis Type="Italic">Post-mortem</Emphasis> Storage and Anesthesia

The present study investigated the effects of sequential collection of milt, time of post-mortem storage and anesthesia on rainbow trout (Oncorhynchus mykiss) sperm motility parameters (using computer-assisted sperm analysis – CASA) as well as seminal plasma osmolality and sperm concentration. The post-mortem storage and time of anesthesia altered motility characteristics of rainbow trout sperm to different extents. The moderate impact of time of anesthesia was manifested in a shortened duration of sperm motility after 10 min exposure of fish to anesthetic. The prolonged post-mortem storage (≥40–60 min), in addition to lowering sperm motility duration, also significantly influenced sperm motility parameters, such as sperm velocities, percentage of motile sperm and sperm trajectory parameters. These results clearly demonstrate that when milt from sacrificed fish is used for sperm motility studies, the time of post-mortem storage significantly alters sperm motility characteristics. Since sperm motility rate and swimming velocity could predict fertilizing ability, detrimental effects of prolonged post-mortem storage may lead to reduced fertilization success. Sperm concentration and seminal plasma osmolality were lower in the first fractions and increased with successive collections of milt. It suggests the presence of urine contamination of the first milt fractions which were collected by stripping. Therefore, testing of sperm concentration and/or seminal plasma osmolality should be mandatory while handling stored milt.