渔场鱼量模型的建立     

张虹  董继学 《农机化研究》2005,(5):99-100

微分方程的平衡点可分为稳定和不稳定两种。当轻轻扰动平衡点时，系统状态就会剧烈变化。若新的状态决不会回到原平衡点，此点就是不稳定的；相反，如果一个系统在稳定平衡点附近受到干扰，它总是企图回到平衡点，那么此点就是稳定的。用这一数学工具可以解决诸如渔场鱼量等一系列实际问题。  相似文献   

用鱼肌核酸指示水体污染的初步研究     

甘居利  金有坤 《农业环境科学学报》1997,(2)

选择了4种家鱼作指示生物，用紫外分光光度法测定其白肌中RNA和DNA的含量。结果表明：同种鱼，污染区的RNA含量显著低于对照区，白鲢和鳊鱼白肌中RNA／DNA低于对照区；不同种的鱼，污染区鱼肌核酸比对照区下降的程度有鳊鱼＞白鲢＞鲫鱼和鲤鱼的趋势。鱼肌核酸下降同水体重金属污染有一定联系，RNA是比RNA／DNA更合适的指标，鳊鱼和白鲢是比鲫鱼和鲤鱼更敏感的指示生物。  相似文献   

对缺硼反应不同的油菜基因型根系吸收硼特性的研究   总被引：5，自引：0，他引：5  

曹享云  刘武定 《华中农业大学学报》1997,16(5):335-339

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埃塞俄比亚芥与白菜,芥菜间的可交配性     

孟金陵  王萍 《华中农业大学学报》1992,11(3):203-207

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长春地区梅花鹿毕氏肠微孢子虫分子流行病学调查     

李建栋  崔凯  董焕声  马泽芳 《中国畜牧兽医》2021,(1)

为了掌握长春地区梅花鹿毕氏肠微孢子虫(Enterocytozoon bieneusi)的感染率及基因型种类的分布情况,探究其在人与动物之间传播的源由,本研究于2018年12月-2019年12月期间采集长春地区8个养殖场共计538份梅花鹿粪便样品进行毕氏肠微孢子虫的流行病学调查及基因型分析,经PCR鉴定,测序分析、序列拼接比对以及系统进化分析。试验结果表明,长春地区梅花鹿毕氏肠微孢子虫的感染率为17.84%(96/538),不同养殖场的感染率为0~47.96%;研究共发现14种基因型(BEB6、EbpC、Ⅰ、JLD-Ⅲ、JLD-Ⅸ、JLD-ⅩⅤ、JLD-ⅩⅥ、JLD-ⅩⅦ、JLD-ⅩⅧ、JLD-ⅩⅨ、JLD-ⅩⅩ、JLD-ⅩⅪ、JLD-ⅩⅫ和JLD-ⅩⅩⅢ),其中BEB6为优势基因型。应用多位点序列分型(MLST)方法,选择MS1、MS3、MS4以及MS7位点对毕氏肠微孢子虫阳性样本进行多态性和群体遗传结构分析,结果显示,在96份阳性样品中,共有16份阳性分离株在至少2个位点同时扩增成功,形成10个多位点基因型(multilocus genotypes,MLGs),相同的基因型之间存在不同亚型,表明长春地区梅花鹿毕氏肠微孢子虫具有丰富的遗传多样性。本研究应用分子生物学方法对长春地区梅花鹿毕氏肠微孢子虫的流行病情况及基因型进行分析,研究结果不仅为梅花鹿毕氏肠微孢子虫防控提供科学依据,也为防控毕氏微孢子虫在人和动物间的传播提供基础数据,对保障公共卫生与健康意义重大。  相似文献   

Effects of different lighting on reproductive system in depressive female rats     

DI Guan-teng  WANG Sha-li 《园艺学报》2016,32(3):510-515

AIM: To investigate the effects of different lighting on the reproductive system in depressive female rats. METHODS: Healthy adult female rats were randomly chosen as control group, and the depressive adult female rats in SPF grade were randomly divided into 5 groups(7 rats each):depressive model group, sulfur lamp group, heat radiation lamp group, fluorescent lamp group and LED lamp group. After 45 d of continuous illumination, the estrous cycle was observed by the vaginal exfoliated cells, and the organ indexes of ovary and uterus were calculated. The concentrations of estiadrol(E₂), prolactin(PRL), progesterone(PROG) and testosterone(T) in the serum were detected by ELISA, and the histopathological lesion of ovary was observed under microscope with HE staining. RESULTS: The estrous cycle exhibited serious disorder, the ovaries exhibited serious congestion, and the organ indexes of ovary and uterus and the concentrations of E₂, PRL, PROG and T decreased significantly in the rats in depressive model group compared with control group(P<0.05). The estrous cycle and histopathological damage of ovary were obviously improved, and the concentrations of E₂, PRL, PROG and T were significantly increased after the sulfur lamp lighting in the depressive female rats compared with depressive model group. No obvious change and improvement of the reproductive functions in the heat radiation lamp group, fluorescent lamp group and LED lamp group was observed. CONCLUSION: The reproductive functions of depressive female rats are improved by sulfur lamp lighting.  相似文献   

Numerical simulation of deformations and forces of a floating fish cage collar in waves     

《Aquacultural Engineering》2016

The dynamic behavior of a fish cage collar in waves was investigated using a numerical model based on the finite element method. The floating collar and mooring system were divided into a series of line segments modeled by straight massless model segments with a node at each end. To verify the validity of the numerical model, research data from other authors were cited and compared with the simulated results, the comparison of results showed a good agreement. The numerical model was then applied to a dynamic simulation of a floating cage collar in waves to analyze its elastic deformation and mooring line tension. The simulated results indicated that the greatest deformation of the collar taken place in the position of the mooring line connection point when incident waves were in the same direction. An increase in the length of mooring line would help to decrease the mooring line tension of the collar. Furthermore, the effects of collar dimension, including collar circumference, pipe diameter in cross-section, and pipe thickness, on the dynamic behavior of the floating collar were discussed. The results of this study provided a better understanding of the dynamic behavior of the fish cage collar.  相似文献   

Extensive dispersal of Roanoke logperch (Percina rex) inferred from genetic marker data          下载免费PDF全文

James H. Roberts  Paul L. Angermeier  Eric M. Hallerman 《Ecology of Freshwater Fish》2016,25(1):1-16

The dispersal ecology of most stream fishes is poorly characterised, complicating conservation efforts for these species. We used microsatellite DNA marker data to characterise dispersal patterns and effective population size (N_e) for a population of Roanoke logperch Percina rex, an endangered darter (Percidae). Juveniles and candidate parents were sampled for 2 years at sites throughout the Roanoke River watershed. Dispersal was inferred via genetic assignment tests (ATs), pedigree reconstruction (PR) and estimation of lifetime dispersal distance under a genetic isolation‐by‐distance model. Estimates of N_e varied from 105 to 1218 individuals, depending on the estimation method. Based on PR, polygamy was frequent in parents of both sexes, with individuals spawning with an average of 2.4 mates. The sample contained 61 half‐sibling pairs, but only one parent–offspring pair and no full‐sib pairs, which limited our ability to discriminate natal dispersal of juveniles from breeding dispersal of their parents between spawning events. Nonetheless, all methods indicated extensive dispersal. The AT indicated unrestricted dispersal among sites ≤15 km apart, while siblings inferred by the PR were captured an average of 14 km and up to 55 km apart. Model‐based estimates of median lifetime dispersal distance (6–24 km, depending on assumptions) bracketed AT and PR estimates, indicating that widely dispersed individuals do, on average, contribute to gene flow. Extensive dispersal of P. rex suggests that darters and other small benthic stream fishes may be unexpectedly mobile. Monitoring and management activities for such populations should encompass entire watersheds to fully capture population dynamics.  相似文献   

Multiple watershed alterations influence fish community structure in Great Plains prairie streams          下载免费PDF全文

Joshuah S. Perkin  Matthew J. Troia  Dustin C.R. Shaw  Joseph E. Gerken  Keith B. Gido 《Ecology of Freshwater Fish》2016,25(1):141-155

Stream fish distributions are commonly linked to environmental disturbances affecting terrestrial landscapes. In Great Plains prairie streams, the independent and interactive effects of watershed impoundments and land cover changes remain poorly understood despite their prevalence and assumed contribution to declining stream fish diversity. We used structural equation models and fish community samples from third‐order streams in the Kansas River and Arkansas River basins of Kansas, USA to test the simultaneous effects of geographic location, terrestrial landscape alteration, watershed impoundments and local habitat on species richness for stream‐associated and impoundment‐associated habitat guilds. Watershed impoundment density increased from west to east in both basins, while per cent altered terrestrial landscape (urbanisation + row‐crop agriculture) averaged ~50% in the west, declined throughout the Flint Hills ecoregion and increased (Kansas River basin ~80%) or decreased (Arkansas River basin ~30%) to the east. Geographic location had the strongest effect on richness for both guilds across basins, supporting known zoogeography patterns. In addition to location, impoundment species richness was positively correlated with local habitat in both basins; whereas stream‐species richness was negatively correlated with landscape alterations (Kansas River basin) or landscape alterations and watershed impoundments (Arkansas River basin). These findings suggest that convergences in the relative proportions of impoundment and stream species (i.e., community structure) in the eastern extent of both basins are related to positive effects of increased habitat opportunities for impoundment species and negative effects caused by landscape alterations (Kansas River basin) or landscape alterations plus watershed impoundments (Arkansas River basin) for stream species.  相似文献   

Ecological impacts of small hydropower plants on headwater stream fish: from individual to community effects          下载免费PDF全文

Lluís Benejam  Sandra Saura‐Mas  Mònica Bardina  Carolina Solà  Antoni Munné  Emili García‐Berthou 《Ecology of Freshwater Fish》2016,25(2):295-306

Hydroelectricity is increasingly used worldwide as a source of renewable energy, and many mountain ranges have dozens or hundreds of hydropower plants, with many more being under construction or planned. Although the ecological impacts of large dams are relatively well known, the effects of small hydropower plants and their weirs have been much less investigated. We studied the effects of water diversion of small hydropower plants on fish assemblages in the upper Ter river basin (Catalonia, NE Spain), which has headwater reaches with good water quality and no large dams but many of such plants. We studied fish populations and habitat features on control and impacted reaches for water diversion of 16 hydropower plants. In the impacted reaches, there was a significantly lower presence of refuges for fish, poorer habitat quality, more pools and less riffles and macrophytes, and shallower water levels. We also observed higher fish abundance, larger mean fish size and better fish condition in the control than in impacted reaches, although the results were species‐specific. Accordingly, species composition was also affected, with lower relative abundance of brown trout (Salmo trutta) and Pyrenean minnow (Phoxinus bigerri) in the impacted reaches and higher presence of stone loach (Barbatula quignardi) and Mediterranean barbel (Barbus meridionalis). Our study highlights the effects of water diversion of small hydropower plants from the individual to the population and community levels but probably underestimates them, urging for further assessment and mitigation of these ecological impacts.  相似文献