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鄱阳湖典型湿地植被景观格局的时空变化分析 总被引：1，自引：0，他引：1
鄱阳湖是我国重要的湿地,对生态、水位控制、环境控制具有重要的调节作用.伴随着水位年际变化和季节变化剧烈,鄱阳湖湿地类型发生了显著变化,研究其景观格局变化对于正确认识鄱阳湖湿地生态系统演变,为湿地景观规划、湿地生态系统健康恢复具有重要参考意义。考虑到鄱阳湖湖相季节性变化巨大以及2003年前后三峡水利枢纽工程运行后水文情势发生重大变化,选取2003年前后平均水平年对应枯水期和丰水期遥感影像,采用遥感技术（RS）、地理信息技术（GIS）和景观生态学方法进行分析。结果表明,江湖关系发生重大变化后,鄱阳湖年平均水位由2002年之前的13.42 m（星子站吴淞高程）降至12.35 m,平均水位较前一阶段偏低0.45~2.25 m,枯水现象使得鄱阳湖水域面积明显缩小,湿地类型发生了较大变化。平均水位下降,适合植被生长的洲滩面积大幅增加,丰水期湿生植被面积增加了147.66 km2,枯水期增加了1192.43 km2,变化最大区域位于赣江支口与饶河交汇处的三角洲和赣江南支口的洲滩,消失的水面大多转换为湿生植物、挺水植物和泥滩等湿地类型。湿地类型的演变方式为水体和挺水植物演变为裸露泥滩,泥滩演变为湿生植被,湿生植被演变为其它湿地类型。2003年后除水体外湿地景观边界密度和聚集度指数呈现增大趋势,鄱阳湖景观格局整体上趋于复杂。鄱阳湖湿地景观格局变化受到“五河”来水减少、三峡工程蓄水和湿地地貌改变等自然因素和人为因素的双重影响。 相似文献
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我国湖泊分布很广,面积很大,其中栖息繁衍的鱼类种类很多,有些大湖(如洞庭湖、太湖、鄱阳湖)均在100种以上。可以进行鱼类等经济水生生物增养殖的湖泊数量很多,总面积约2,800余万苗。湖泊是我国淡水渔业生产的重要水域,湖泊渔业生产历史上多是以捕捞自然鱼类为主,由于对水域生态效益的忽视,对水产生产的重视不够,并一度受“以粮为纲”的影响,围湖造田,水利、水工设施闸坝的阻隔,致水域面积缩小, 相似文献
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基于2007-2017年5期遥感影像,运用遥感解译和景观指数方法,探究运城黄河湿地景观格局变化及其驱动因素,为黄河中游河道湿地的修复与可持续利用提供参考。结果表明:(1)湿地面积在2007-2017年期间总体呈增长趋势,其中2007-2015年湿地面积持续上升,面积增加9 041.39 hm^2,2015-2017年减少5 716.08 hm^2。湿地与旱地之间转换最密切,湿地景观间(水域+沼泽+草甸)也有较大幅度的转换。景观类型的分布以河津市、万荣县、永济市及垣曲县部分种类偏多,湿地景观沿河流分布。(2)类型水平上,旱地是优势类型,湿地整体处于劣势,景观零碎。水域在湿地景观中占优势,林地、旱地景观趋于复杂,旱地、水域、林地景观集聚度偏大;景观水平上,研究区景观破碎度和复杂度都有不同程度的降低,结构趋于稳定,连通性变好。(3)景观格局变化主要受人为驱动影响,其中政策对研究区有强制性的作用。近10 a运城黄河湿地呈现增长态势,景观格局总体逐渐优化。 相似文献
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“搞渔政工作很辛苦,很劳累,很光荣。你们人在鄱阳湖,要热爱鄱阳湖,管好鄱阳湖”。“渔政工作是沿湖各级党政领导的一项重要工作,要一年一年抓下去,一代一代抓下去”。这是吴官正省长3月12日上午看望奋斗在鄱阳湖区渔政管理第一线的全体干部、职工时讲的一番话。 相似文献
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我国湖泊分布很广，面积很大，其中栖息繁衍的鱼类种类很多，有些大湖(如洞庭湖、太湖、鄱阳湖)均在100种以上。可以进行鱼类等经济水生生物增养殖的湖泊数量很多，总面积约2，800余万苗。湖泊是我国淡水渔业生产的重要水域，湖泊渔业生产历史上多是以捕捞自然鱼类为主，由于对水域生态效益的忽视，对水产生产的重视不够，并一度受“以粮为纲”的影响，围湖造田，水利、水工设施闸坝的阻隔， 相似文献
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一、引发鱼类疾病的各种水体因素1.养殖水体的空间因素养殖水域是水产动物的活动场所。在池塘养殖中,每个养殖动物所拥有的活动场所的大小,取决于水域的面积、水深及放养密度、种类和规格。俗话说“宽水养大鱼”,即明确地表明了水体空间小时,会抑制其生长和发育,体质也变弱。同 相似文献
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长江是我国鱼类多样性最高的河流，同时也是我国最重要的淡水渔业资源产区。然而，近几十年来受水域污染、水工程建设、湖泊围垦、航运发展、过度捕捞和外来种入侵等多重因素的影响，长江流域生态系统面临着逐渐衰退的困境，主要表现为鱼类种类数减少、鱼类濒危物种程度加剧、鱼类资源小型化趋势明显、鱼类资源呈衰退趋势和外来物种种类增多等。长江十年禁渔，对恢复长江水生态环境和保护水域生物多样性提供了重要的机遇。作者建议统筹协调长江生态保护与渔业发展的关系，创新流域管理体制与机制，根据长江水生态系统结构与功能变化，适时调整服务目标，其目的旨在实现对长江流域水生态环境的保护和渔业资源的可持续发展提供科学依据。 相似文献
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Cu2+对大型蚤生长和繁殖的影响 总被引：1，自引：0，他引：1
研究了不同浓度Cu2+对大型溞生长和繁殖的毒性影响.试验观察了大型溞的繁殖指标(产第1胎时间、每只溞所产总幼溞数、每只溞所产总胎数和内禀增长率),同时还观察了存活和生长(体长)2个指标.试验结果显示,随着Cu2+浓度的增加,内禀增长率显著F降,但是生长和存活仅在9.6μg/L Cu2+浓度下显著下降.产第1胎时间随Cu2+浓度增加而延长;表明Cu2+低浓度下对水生生物的长期慢性影响不容忽视.大型溞繁殖指标可作为水环境Cu2+污染预警生物标志. 相似文献
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Frederick W. Goetz Alexis Y. Fostier Bernard Breton Bernard Jalabert 《Fish physiology and biochemistry》1987,3(4):203-211
The plasma levels of estradiol-17 (E2), 17, 20-dihydroxy-4-pregnen-3-one (17,20-P) and gonadotropin (GTH) were measured in brook trout (Salvelinus fontinalis) during the period from the end of vitellogenesis to postovulation. Blood samples were taken according to specific stages of maturation, including germinal vesicle breakdown (GVBD) and ovulation. E2 levels were quite high (45 ng/ml) at the end of vitellogenesis (and prior to GVBD) and dropped precipitously by GVBD (2 ng/ml). They remained low through ovulation and postovulation. 17,20-P levels were low prior to GVBD (0.7 ng/ml) and increased dramatically at GVBD (148 ng/ml). The levels of 17,20-P remained high at ovulation (142 ng/ml) and then dropped significantly within 24 h to approximately half of the ovulatory values. They decreased even further by 7 days postovulation. GTH levels rose gradually through GVBD and ovulation from a postvitellogenic level of approximately 3 ng/ml to a 7 day postovulatory value of approximately 10 ng/ml. The overall results; 1) decrease in estradiol prior to GVBD, 2) increase in 17,20-P at GVBD and 3) gradual GTH rise through GVBD and ovulation, are similar to those reported for other salmonids. 相似文献
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为研究中草药复合添加剂“富康163”对水库网箱养殖靬金鳟和虹鳟生长效果的影响,分别设置了两个试验箱和对照箱。试验箱添加2%“富康163”,在水温13℃～20℃条件下,经42d的养殖试验,结果表明,相同含量的“富康163”对不同饲养密度的网箱养殖靬金鳟和虹鳟的增重倍数、日平均增长率、饲料系数和成活率均产生不同程度的影响,其中以放养密度高的虹鳟试验箱增产效果尤为显著。 相似文献
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B.M. Amiri M. Maebayashi S. Adachi G.P. Moberg S.I. Doroshov K. Yamauchi 《Fish physiology and biochemistry》1999,21(1):1-14
In this study, developmental changes in the steroidogenic capacity of testicular fragments and isolated ovarian follicles of a hybrid sturgeon, Bester, at a variety stage of developments were examined. Testicular fragments or isolated ovarian follicles were incubated in L-15 medium in the presence or absence of different concentrations of five preparations; forskolin, human chorionic gonadotropin (HCG), pregnenolone (P5), 17-hydroxyprogesterone (17OHP) and testosterone (T) for 18 h at 15 °C. After incubation, concentrations of 11-ketotestosterone (11 KT) (testis) and, 17-estradiol (E2) (ovarian follicles) and 17,20-dihydroxy-4-pregnen-3-one (DHP) (testis and ovarian follicles) were measured. 11KT was detected in the media following incubation with P5, 17OHP and T. Its concentration was higher during late spermatogenesis and prespermiation and lower at the degeneration stage. Both P5 and 17OHP were converted to DHP during the prespermiation stage. Forskolin had little stimulatory effect on the synthesis of 11KT and DHP and HCG did not induce the production of these steroids.E2 was detected in the medium following incubation of follicles with P5, 17OHP and T at all stages of oocyte development. The concentration of E2 in the medium increased during vitellogenesis with the peak production occurring at the tertiary yolk stage. In contrast, the potencies of follicles to produce steroids shifted to the production of DHP during migratory nucleus stage. Forskolin and HCG had little effect on the synthesis of E2 and DHP. These results demonstrated that the failure of spontaneous spermiation or ovulation is not due to the insufficient synthesis of DHP, but may due to the lack of availability of precursors. 相似文献
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"三渔问题"与渔业管理制度——基于辽东湾海蜇捕捞的考察 总被引：1，自引：0，他引：1
相比"三农问题","三渔问题"远未获得重视.文章通过对辽东湾海蜇捕捞的考察,沿着渔业资源的特征这条主线,深入地探讨渔民的经济行为和社会冲突,揭示现存海蜇管理制度的缺陷.笔者认为,对于辽东湾海蜇捕捞,基于产权的渔业共同管理模式是一种有效的方案. 相似文献
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淡水养殖梭鱼的人工繁殖机理 总被引：1，自引：1，他引：1
1982～1986年;作者采用外源药理学方法,使淡水养殖梭鱼(S‰0.297-0.569)克服了“淡水不育症”,雌鱼性腺成熟率85％以上,完全取代了“海水过渡”。在人工催产中又克服了排卵机制的障碍及胚胎对环境的不适应,并对梭鱼亲鱼血清激素含量进行放射免疫(RIA)测定及电子显微镜对梭鱼脑垂体亚显微结构进行观察。提出梭鱼存在血脑屏障。 相似文献
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The objective of this study was to investigate the effects of sex steroids on spermiation in protandrous male black porgy, Acanthopagrus schlegeli. Experiments on common carp (Cyprinus carpio) were also conducted for comparison. Fifty male black porgy were divided into 5 groups and injected with a superactive analogue of mammalian luteinizing hormone releasing hormone (LHRH-A), 17,20,21-trihydroxy-4-pregnen-3-one (20-S), 17,20-dihydroxy-4-pregnen-3-one (17,20-DHP), 11-ketotestosterone (11-KT) or saline. The dosage of the sex steroids given on days 0, 2, 4 and 6 was 330, 330, 990 and 1980 µg kg-1 body weight, respectively. Milt volume and sperm concentrations were measured on days 0, 2, 4, 6, 8 and 10. Similar treatments were also conducted in 45 male common carp. Milt volume was significantly increased in black porgy after treatment with 20-S and 17,20-DHP; 17,20-DHP had stimulatory effects on spermiation at a lower dose (900 µg kg-1 body weight, p < 0.05) as compared to 20-S (1980 µg kg-1 body weight, p < 0.01). In the common carp, milt volume was also increased after treatment with LHRH-A and 17,20-DHP but not with 20-S. 17,20-DHP stimulated spermiation at a lower dose in common carp (330 µg kg-1 body weight) than in black porgy (990 µg kg-1 body weight). However, 11-KT did not stimulate spermiation in black porgy or common carp. The concentrations of plasma 11-KT could immediately reflect to the administration of exogenous 11-KT in black porgy. 相似文献
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Effective non-bicarbonate buffering capacity (or buffer value) was measured in white muscle of yellow perch (Perca flavescens) by titrations with mineral acid and base in a carbon-dioxide free, closed system. Yellow perch were collected at three month intervals throughout 1983 from an acidic lake (pH 4.6) and two alkaline lakes (pH 7.8) in northern Wisconsin. Buffering capacity was also determined for white muscle of perch kept in the laboratory under different regimes of temperature and ration. The mean buffering capacity of white muscle from yellow perch taken directly from natural environments ranged from 40.7 ± 3.1 (SD) slykes in March of 1983 to 53.7 ± 2.8 (SD) slykes in July of that year. These changes in buffering capacity were strongly correlated with water temperature. Egg production and thirty-day laboratory starvation produced significant decreases in buffering capacity and increases in the water content of yellow perch muscle. Fed perch in the laboratory had a temperature dependent buffering capacity similar to field caught fish. Buffering capacity of white muscle did not differ between yellow perch from acidic and alkaline lakes. Investigators using buffering capacity as a gauge of species differences in metabolic potential, should be wary of seasonal and reproductive factors that might alter their conclusions. 相似文献
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P.K. Reddy A.C. Holloway R. Renaud J.F. Leatherland 《Fish physiology and biochemistry》1999,21(3):211-222
Ovarian follicles taken from sexually maturing rainbow trout at the mid-vitellogenic stage of ovarian development were incubated in vitro in the presence or absence of melatonin or somatostatin-14 (SRIF-14) to determine whether there is evidence of a direct action of these factors on gonadal steroidogenesis in fishes. The steroidogenic capacity of the ovarian follicles was assessed by measuring testosterone (T) and 17-estradiol (E2) release into the incubation medium, and by examining the steroid metabolites produced following incubation of follicles with radiolabelled steroid precursors.Melatonin appears to elicit a biphasic effect on steroidogenesis by in vitro rainbow trout ovarian follicles; at a concentration of 1 × 10–3 M, melatonin stimulated basal T and E2 production, but at a concentration of 1 × 10–2 M there was an inhibition of basal and sGtH-stimulated T and E2 Melatonin may act to reduce the activity of specific steroidogenic enzymes, since there was evidence of melatonin at 1 × 10–2 M enhancing the accumulation of [3H]17-hydroxyprogesterone in the medium following incubation with [3H]pregnenolone, possibly suggesting the inhibition of C17,20-lyase activity. In contrast, SRIF-14, used at concentrations of 1 × 10–8 M and 1 × 10–6 M, had no effect on basal or sGtH-stimulated E2 or T production by ovarian follicles, incubated in vitro. 相似文献