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青虾生长规律与群体组成的研究 总被引：10，自引：3，他引：10
报道了上海川沙县孙桥河道青虾的生长呈明显的阶段性,如雄虾的第一阶段（1990年6—11月）的生长方程为L_t=3.38[1-e~(-0.4943(t+0.1674)];第二阶段（1991年2—6月）的生长方程为L_t=6.57/(1+e~(2.1805-0.2787t);它们的拐点分别为2.07月龄和11.97月龄。渔获群体分析结果表明,月龄为0-15月,体长范围为1.30—6.58cm,体重范围为0.060—13.39g;一年出现两个群体,其中夏季群体生活期从当年7月至翌年10月,数量大,占群体数量80％以上;秋季群体生活期从当年9月至翌年12月,约占群体数量20％左右。群体中一般雄虾数量多于雌虾数量,月性比(?)在0.61—1.35之间变动。 相似文献
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太湖大银鱼生长特性的研究 总被引：12，自引：1，他引：12
本文根据太湖大银鱼(Protosalanx hyalocranius Abbott)周年生物学实测资料,并应用Von Bertalanffy生长方程进行计算,对大银鱼在太湖的生长规律及特点进行分析探讨,结果表明:1.体全长与体重呈幂函数关系:W=3.981×10~(-6)L~(2.9359);2.Von Bertalanffy生长方程的各项参数值为:L_∞=219.86(mm),W_∞=28.56(g),K=0.1469,t_0=0.33;3。生长拐点年龄为7、8月龄。 相似文献
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对湖北省阳新县网湖所采得的862尾似刺鳊鮈的年龄与生长的研究表明,其年轮特征主要为切割型和碎裂型。其体长与鳞径呈直线相关:L=5.6784+4.3056R;体长与体重呈幂函数的增长关系:W=2.8026×10~(-2)L~(2.8754)。应用Van Bertalanffy生长方程拟合该鱼的一般生长规律,其生长参数为:L_∞=25.0143cm,W_∞=277.8876g,K=0.4668,t_0=-1.3886,拐点年龄t_i=1龄,拐点体长L_i=16.42cm,拐点体重W_i=82.82g。 相似文献
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大水面日本沼虾(Macrobrachium nipponensis)资源人工增殖 总被引：4，自引：0，他引：4
挑选受精卵颜色呈褐色或接近褐色的抱卵虾,放入网箱多点布局孵化,直接放流孵出幼体是大水面日本沼虾资源增殖的有效方法.2001年,采用此法对湖北省阳新县网湖日水沼虾进行增殖,其产量从增殖前(2000年)的10000kg上升至35000kg,取得显著增殖效果,进箱孵化的抱卵数量(N,kg)可用计划生产量(Y,kg),总回捕率(R)及个体平均体重(W,g/ind)计算:N≥Y·(1000·R·W)-1. 相似文献
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水丰水库亚洲公鱼和大银鱼种群生态的比较研究 总被引：4，自引：0，他引：4
1998年 10月至 2 0 0 0年 11月对水丰水库亚洲公鱼和大银鱼的食性、生长、繁殖、群体结构进行了比较研究 .亚洲公鱼为杂食性鱼类但主要以浮游动物为食 ,繁殖时还摄食同类卵 ,出现频率达 4 2 .9% ,在冬季也摄食大银鱼卵 (2 .8% ) ;体长 (L)、体重 (W)呈异速生长 (W =1.176×10 - 6 L3.5555) ;群体繁殖速度比 1984年以前提高了 4 9.2 % ;群体结构中体长、体重的离散度很小 .大银鱼前期主要以浮游动物为食 ,后期以小鱼小虾为主要食物 ,也捕食公鱼 ,出现频率 6 .9% -9 6 % ;体长、体重呈等速生长 ,W =4 .4 82× 10 - 6 L3.0 0 0 9;群体繁殖速度高出公鱼 1.18倍 ;群体结构中体长、体重的离散度较大 ,表现出了个体间的差异性 相似文献
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2002-2004年，在浙江衢州铜山源水库，对该库放养的美国大口胭脂鱼的生长情况进行了研究，结果表明，该水 库美国大口胭脂鱼的鳞片以环片的切割型为主要年轮特征．用刺网所捕的美国大口胭脂鱼渔获物中以Ⅱ、Ⅲ、Ⅳ龄个体为 主．体长和体重的关系式为：W=8．595×10~(-5)15 L~(2.662)，Von Bertalanffy 生长方程的主要生物学参数：L_∞=36．54cm，W_∞= 1．245kg，K=0．6377，t_0=-0．261龄，体重生长的拐点年龄 t_1=1．92龄，拐点体重W_1=0．396kg．与池养鱼类生长情况相 比，铜山源水库的美国大口胭脂鱼生长较慢． 相似文献
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新疆乌伦古湖河鲈二十年来种群生长变化及原因 总被引：2，自引：0，他引：2
新疆乌伦古湖是中国内陆主要渔业基地之一,为了充分开发其渔业资源,在过去的40余年中共引进鱼类15种;乌伦古湖土著鱼类的生态位大部分已经为外来鱼类所占据,曾为乌伦古湖最重要的土著经济鱼类的河鲈物种濒临灭绝,为了探讨河鲈种群数量锐减的原凶和外来鱼类对乌伦古湖土著鱼类的入侵机制,2007-2008年对乌伦古湖河鲈的生长状况进行了调查,并与1987-1989年的调查数据进行了比较分析,调查结果表明:除1+龄组外,乌伦古湖河鲈其它各龄组的平均体长和体重均明显减小;拟合Von Bertalanffy生长方程的各参数,L∞=41.317cm,W∞=15475.1g,k=0.1649,t0=-0.2626;求得生长特征指数Φ=2.4493.L∞和Φ值明显减小,k值有所增加;但生长式型没有改变,生长拐点与1987-1989年一致,仍为tIP=7.探讨了乌伦古湖河鲈种群生长变化的主要原因及作用机制. 相似文献
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栖息地退化和外来物种入侵都是淡水生态系统中的主要威胁因素,因此,量化不同人类活动干扰强度下外来入侵生物和本土生物的食性组成差异,对于明确种间竞争强度,制定适合的管理对策至关重要.本研究应用碳、氮稳定同位素分析技术,比较了长江中下游西洞庭湖湿地受人类活动干扰程度不同的天然湿地和人工改造湿地中的入侵种克氏原螯虾(Procambarus clarkii)与本土种日本沼虾(Macrobrachium nipponense)的食性组成及差异.2017年8月8-18日在西洞庭湖区不同人类干扰强度的栖息地中采集了两种消费者和5种潜在食物来源样品,共计91个.测定碳氮稳定同位素含量后,使用贝叶斯混合模型,估算不同食物来源对消费者的贡献.研究发现:在两种栖息地中克氏原螯虾与日本沼虾食性均有重叠,且在改造湿地中重叠度更大.与克氏原螯虾相比,日本沼虾消费更多的动物性食物.与天然湿地相比,在改造湿地中由于克氏原螯虾数量更多,与本土种竞争食物资源,克氏原螯虾和日本沼虾δ13 C比值都显著升高,食性组成均发生了变化,植物性食物来源比重增加.由于食性改变,在改造湿地中仅日本沼虾δ15 N比值显著下降,克氏原螯虾在两种栖息地中δ15 N比值无显著变化.本研究证明,随着人类干扰强度增大,受干扰湿地中外来入侵生物对本土生物的影响增大. 相似文献
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阪神·淡路大震灾后 ,日本着手对原有的地震观测体制作彻底改革 ,多项全国性配置地震计的计划同时开始启动。地震引起的地面晃动的程度不尽相同 ,无感微小地震引发的晃动仅有 0 .0 0 1 μm,频率为1 0 Hz;巨大地震引起的地面晃动的幅度高达 2～ 3 m,周期也有几十秒。虽说都称之为地震计 ,但由于地震动的振幅和频率涉及的范围太大 ,所以应针对观测对象选用不同类型的地震计。下面介绍不同类型的观测网。1 强震观测网 ( K- NET)无论大地有多大的晃动都能将其准确记录下来的地震计称之为强震计。它构造坚实 ,信号明确 ,通常设置在地表 ,对了… 相似文献
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Sun, climate, hunger, and mass migration 总被引：9，自引：1，他引：8
Kenneth J. Hsu 《中国科学D辑(英文版)》1998,41(5):449-472
Paleoclimatic studies indicate four epochs of global cooling during the last 4 000 years, i. e. during the few centuries before
and after 2000 BC, 800 BC, 400 AD, and 1 600 AD; the quasiperiodicity corresponds to cyclic variation of solar activity. Global
temperature changes influenced regional precipitation patterns: Northern Europe was wetter while the middle- and low-latitude
lands were more arid during colder epochs. Both sets of cold climatical conditions were unfavorable for agricultural production.
Historical records show that large demographic movements in history took place because of crop failures and mass starvation,
rather than escaping from war zones. The “wandering” of the Germanic tribes during the first two or three centuries of the
Christian Era is one example. Whereas the accelerated release of carbon dioxide from the burning of fossil fuels is ultimately
to cause global warming, historical evidence indicates, however, that global warming has been on the whole a blessing to mankind.
Global cooling, on the other hand, has curtailed agricultural production and has led to famines and mass migrations of people.
Perhaps the most important task at the present is not so much computer-modelling of greenhouse effect on global climate, but
water-management and agricultural researches to insure food-supply for an everincreasing world population. 相似文献
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Michael O. Garcia Diane Hanano Ashton Flinders Dominique Weis Garrett Ito Mark D. Kurz 《Bulletin of Volcanology》2012,74(6):1445-1463
The size, shape, and magmatic history of the most recently discovered shield volcano in the Hawaiian Islands, Mahukona, have been controversial. Mahukona corresponds to what was thought to be a gap in the paired sequence (Loa and Kea trends) of younger Hawaiian volcanoes (<4?Ma). Here, we present the results of marine expeditions to Mahukona where new bathymetry, sidescan sonar, gravity data, and lava samples were collected to address these controversies. Modeling of bathymetric and gravity data indicate that Mahukona is one of the smallest Hawaiian volcanoes (～6,000?km3) and that its magmatic system was not focused in a long-lived central reservoir like most other Hawaiian volcanoes. This lack of a long-lived magmatic reservoir is reflected by the absence of a central residual gravity high and the random distribution of cones on Mahukona Volcano. Our reconstructed subsidence history for Mahukona suggests it grew to at least ～270?m below sea level but probably did not form an island. New 40Ar–39Ar plateau ages range from 350 to 654?ka providing temporal constraints for Mahukona’s post-shield and shield stages of volcanism, which ended prematurely. Mahukona post-shield lavas have high 3He/4He ratios (16–21?Ra), which have not been observed in post-shield lavas from other Hawaiian volcanoes. Lava compositions range widely at Mahukona, including Pb isotopic values that straddle the boundary between Kea and Loa sequences of volcanoes. The compositional diversity of Mahukona lavas may be related to its relatively small size (less extensive melting) and the absence of a central magma reservoir where magmas would have been homogenized. 相似文献
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In this study, we have checked the location and focal depth of the Yecheng earthquake (m b = 6.0, maximum intensity VII) of February 14, 1980. The result shows that this is an intermediate event with a focal depth of 90 km. The microepicenter is located at 36. 4°N, 76, 9°E, while the macroepicenter is at 37.3°N, 76.9°E, 90 km to the north of the microepicenter. This is the first destructive intermediate event in China which led to a damage as severe as of intensity VII. The focal mechanism of the event is determined to be of thrust type. Combined with the analysis of seismological and geological data in surrounding area, the possible relation between the event and plate movement has been discussed. The result in this paper indicates that in some particular place, the destructive effect of intermediate event should be considered in seismic hazard assessment. 相似文献
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Dynamics of dissolved major (Na,K, Ca,Mg, and Si) and trace (Al,Fe, Mn,Zn, Cu,and Cr) elements along the lower Orinoco River 
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下载免费PDF全文 Abrahan Mora Jürgen Mahlknecht Juan Carlos Baquero Alain Laraque Juan A. Alfonso Daniel Pisapia Laura Balza 《水文研究》2017,31(3):597-611
This study addresses the changes in dissolved major and trace element concentrations along the Orinoco River, including the mixing zone between the Orinoco and Apure Rivers. Water samples from the Apure and Orinoco Rivers were collected monthly in four sectors over a period of 15 months. Auxiliary parameters (pH, dissolved oxygen, conductivity, and temperature), total suspended sediments, dissolved organic carbon (DOC), and major (Na, K, Ca, Mg, and Si) and trace (Al, Fe, Mn, Zn, Cu, and Cr) element concentrations were measured in all sectors. The relative contribution of both rivers after the Apure–Orinoco confluence was determined using Ca as a tracer. Moreover, a mixing model was developed to determine whether dissolved species exhibit a conservative behavior during mixing. The results indicate that DOC is removed from waters during the Apure–Orinoco mixing, probably due to absorption of DOC on mineral phases supplied by the Apure River. Dissolved Na, Ca, and Mg behave conservatively during the mixing processes, and their concentrations are controlled by a dilution process. The anomaly in the temporal pattern of K in the Orinoco is caused by the input of biogenic K originating from the Apure River during the high‐water stage. The loss of dissolved Si during the low‐water stage can be explained by the uptake of Si by diatoms. Dissolved Mn, Zn, Al, and Fe showed a non‐conservative behavior during the Apure–Orinoco mixing. The removal of Mn and Zn from the dissolved phase can be explained by the formation of Mn‐oxyhydroxides and the scavenging of Zn onto Mn oxides. Dissolved Fe is controlled by redox processes, although the removals of Fe and Al due to the preferential adsorption of large organometallic complexes by mineral surfaces after the Apure–Orinoco confluence can affect the mobility of both elements during transport. The conservative behavior shown by Cu and Cr can be related to the tendency of both elements to be complexed with small organic colloids, which are not preferentially adsorbed by clays. 相似文献
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Abu Sayeed Shafiuddin Ahmed Mohammad Belal Hossain Saad Mohammad Omar Faruque Babu Moshiur Rahman Jun Sun Mohammad Shafiqul Islam Sarker 《国际泥沙研究》2022,37(1):83-96
Sediment samples from the Gomti River basin were investigated to determine and evaluate trace metal concentrations,their biological effect,and potential ecological and human health risks for adults and children.The mean concentrations of trace metals were organized in the descending order of mercury(Hg)(0.08 mg/kg)>chromium(Cr)(0.06 mg/kg)>lead(Pb)(0.05 mg/kg)>arsenic(As)(0.02 mg/kg)>cadmium(Cd)(0.01 mg/kg).The current study illustrated that metals were attributed to the area from natural sources and different anthropogenic sources especially from industries.However,the concentration levels were lower than the sediment quality guidelines(SQGs)based on the effect-range classifications of threshold effect concentration(TEC)and probable effect concentration(PEC).Therefore,the concentration of the elements showed no adverse biological effects on aquatic organisms.The evaluated potential ecological risk index also revealed the low toxicity to the aquatic environment.Moreover,the applied sediment quality indices,geo-accumulation index(Igeo),contamination factor(CF),and contamination severity index(CSI)suggested that the contamination levels of the elements were in the acceptable range,and the contamination had not notably impacted on the sediment quality.The risk index(HI)concerning age groups was significantly less than the threshold limit of 1 indicating that the contamination had no non-carcinogenic risk effect.The total carcinogenic risk(TCR)was less than a risk value of 1×104.Hence,the current study suggests that immediate remediation is not required due to an absence of alarming conditions in the study area.Proper monitoring of the attribution of the metal elements should be done for the betterment of human and environmental health。 相似文献
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Transitional, entraining, cloudy, and coastal boundary layers 总被引：2，自引：0，他引：2
Wayne M. Angevine 《Acta Geophysica》2008,56(1):2-20
Atmospheric boundary layers are marvelously varied and complex. Recent research has examined some of that variety. Boundary
layers over land undergo drastic changes throughout the day as the sun rises and sets, and as clouds form and dissipate. Air
is entrained at the top of the boundary layer at varying rates. As air moves over the coast, the boundary layer reacts to
changes in surface forcing. All of these changes affect pollutant transport and weather formation. In this paper, research
attempting to understand transitional, cloud-topped, and coastal boundary layers, and boundary-layer top entrainment, is reviewed. 相似文献