共查询到19条相似文献，搜索用时 140 毫秒
1.
探究鱼类繁殖策略是了解鱼类种群动态的关键.通过对珠江西江流域重要的经济鱼类广东鲂(Megalobrama terminalis)生殖周期、产卵时间、成熟期长度、生殖力类型和生殖力等方面进行研究,阐明在人类活动日益加强下,西江广东鲂的繁殖策略适应性变化情况.研究表明,广东鲂个体平均体长245 mm,优势体长集中在260~280 mm,平均体重347 g,优势体重集中在320~480 g.用L 50逻辑斯谛回归方法推算广东鲂雌鱼和雄鱼初次性成熟体长分别为244.5和232.2 mm.雌雄性比例为1.105∶1,且随着体长增加,雌雄性比呈现出先下降后上升的变化趋势.广东鲂繁殖群体在产卵季节为48月,产卵高峰为6月初持续到7月上旬,产卵季节内广东鲂鱼苗的密度与径流量显著相关.广东鲂绝对繁殖力平均为73069粒,相对繁殖力平均为118.7粒/g,绝对繁殖力与体长和体重均呈正相关.广东鲂繁殖群体性腺成熟系数与性腺重、肥满度以及体重密切相关.广东鲂种群繁殖策略在人类活动加剧影响下呈现出适应性变化:初次性成熟体长变小,绝对繁殖力下降. 相似文献
2.
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
3.
本文对繁殖季节的209尾凤鲚标本进行了生物学分析。在采获的标本中,最大体长182mm,体重23.4g;最小体长94mm,体重3.5g。肥满度(k)平均为3.15×10~(-4)。其体长与体重的回归关系式为W=1.174×10~(-5)L~(2.773)。雌鱼的绝对繁殖力平均为7403.48粒,成熟系数为18.92％。雄鱼成熟系数8.02％。绝对繁殖力与体长呈曲线回归关系,F=1.906×10~(-2)L~(2.54),与体重呈直线回归关系,F=688.13W—2119.68。 相似文献
4.
凤鲚繁殖群体的生物学特性及因数关系的研究 总被引：1，自引：0，他引：1
本文对繁殖季节的209尾凤鲚标本进行了生物学分析。在采获的标本中,最大体长182mm,体重23.4g;最小体长94mm,体重3.5g。肥满度（k）平均为3.15×10-4。其体长与体重的回归关系式为W=1.174×10-5L2.773。雌鱼的绝对繁殖力平均为7403.48粒,成熟系数为18.92%。雄鱼成熟系数8.02%。绝对繁殖力与体长呈曲线回归关系,F=1.906×10-2L2.54,与体重呈直线回归关系,F=688.13W—2119.68。 相似文献
5.
湖北牛山湖高体鳑鮍的年龄、生长与繁殖 总被引：2，自引：0，他引：2
研究了牛山湖高体鳑鲏的年龄、生长和繁殖特征. 鳞片上年轮清晰,主要呈现疏密特征.种群年龄结构简单,仅由一个世代组成;雄与雌的比例为1.59∶1(n= 332),显著不同于1∶1(Xc2 ＝16.94, p<0.005)而符合2∶1的类型(Xc2 ＝3.82, p> 0.05). 两性最大寿命不超过2a.雄、雌体全长与体重、全长与体长的回归方程差异显著. 在繁殖期间,雌雄鱼均出现第二性征.雄鱼最小成熟个体的全长和体重分别为26mm、0.216g,雌鱼则分别为32mm、0.393g. 性成熟年龄为1a,属分批产卵类型.成熟卵粒呈葫芦状,长度平均3.31mm. 每尾雌鱼平均繁殖力为61粒,繁殖力与全长及体重均呈显著相关(p＜0.001). 相似文献
6.
太湖湖鲚渔获量变化与生物环境间相互关系 总被引：7，自引：1，他引：6
2003-2004年在汉江中游江段共监测654船次,统计渔获物6914．16 kg,生物学测定1682尾鱼,共采集鱼类78 种,隶属18科58属．目前汉江中游渔获物组成和结构与20世纪70年代相比发生了较大变化,翘嘴红鲌、瓦氏黄颡鱼、鲶、 鲢、黄尾鲴、大鳍蠖等在渔获物中比例已经很少;草鱼资源也明显下降;铜鱼、青鱼、蒙古红鲐、鳡、细鳞斜颌鲴、吻鮈 、长吻 鮠、拟尖头红鲌、鳙、鳜等在渔获物中已基本消失;而鲤、鲫、黄颡鱼、长春鳊、赤服鳟等中小型鱼类在渔获物中的比例却相 对上升;渔获物中个体大的鱼减少,低龄鱼及幼鱼个体比重增加．与70年代资料相比,汉江中游鱼类资源已呈衰退趋势． 相似文献
7.
鄱阳湖产银鱼的繁殖生物学 总被引：7，自引：1，他引：6
本文记述了鄱阳湖产太湖短吻银鱼(Neosalanx tangkahkeii taihuensis)、乔氏短吻银鱼(Neosalanx jordani)、雷氏银鱼(Reganisalanx brachyrostralis)等三种银鱼的成熟年龄、繁殖时期、生殖群体的体长、性比、生殖力、卵的特征等繁殖生物学资料,并记述了太湖短吻银鱼性腺成熟系数的周年变化、太湖短吻银鱼和乔氏短吻银鱼的产卵生态条件等。近二十年来鄱阳湖银鱼产量急剧下降的主要原因是产卵场遭到了严重破坏。银鱼生命周期仅一年,繁殖力强,认为加强繁殖保护、合理安排捕捞时间是恢复鄱阳湖银鱼资源的关键措施。 相似文献
8.
洪湖日本沼虾的种群繁殖生物学 总被引：6，自引：0，他引：6
1994年5月至1995年6月对洪湖日本沼虾的种群繁殖生物学进行了研究．洪湖日本沼虾的繁殖期为4月中旬至10月上旬,5月中旬至8月中旬为日本沼虾的繁殖高峰期,其中6月、8月雌虾抱卵率均在70％以上;日本沼虾群体中雄性总是少于雌性,月性比（♀／♂）变化于1．104－5．780之间,3—6月性比逐渐增高,7─10月性比则逐渐降低;在整个繁殖期．4─7月的抱卵虾均为前一年出生的大、中规格的个体,之后当年出生的个体在繁殖群体中逐渐占据优势;春季抱卵虾的绝对繁殖力和相对繁殖力都大于秋季抱卵虾,分别计算了绝对繁殖力、相对繁殖力与体长、体重的函数关系．本文还对日本沼虾群体性比的周年变化及其产卵次数进行了讨论． 相似文献
9.
太湖大银鱼生长特性的研究 总被引：13，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
10.
《中国科学:地球科学》2017,(4)
作为TTG质岩石的一个重要组成部分,一般认为奥长花岗质岩石是基性岩部分熔融的产物,但在很多TTG片麻岩地体中,如在冀东麻粒岩相区的奥长花岗岩呈较小的岩脉、侵入体,或者呈英云闪长质片麻岩中的浅色体产出,显示近原地熔融成因.本文以冀东地区英云闪长质片麻岩样品J13为基础,并结合锆石定年研究,探讨该区奥长花岗质岩石的成因,模拟在不同压力(0.7、1.0和2.0GPa)下发生的变质熔融反应以及熔体的常量、微量元素成分特征.结果表明,英云闪长质片麻岩在石榴二辉麻粒岩相条件下,如0.9~1.1GPa/800~850℃,发生角闪石脱水熔融,熔融程度为5~10wt.%,残余物中石榴石含量为5~10wt.%时,产生的熔体的成分与冀东奥长花岗质岩石有很大的相似性,如La/Yb值高,Yb含量低等,但模拟熔体的常量元素成分相对高K2O、低CaO、Mg~#偏低,表明冀东奥长花岗岩脉体和浅色体可能包含了部分残余矿物并受到结晶分异的影响.锆石定年结果表明,研究区英云闪长质片麻岩原岩结晶年龄为(2518±12)Ma,变质年龄为(2505±19)Ma,奥长花岗质岩脉的结晶年龄为(2506±6)Ma,二者之间存在密切成因联系. 相似文献
11.
12.
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
13.
实测和回归分析鄱阳湖鲌属(Culter)的翘嘴鲌(C.alburnus)、蒙古鲌(C. mongolicus)、达氏鲌(C.dabryi)和原鲌属(Culterichthys)的红鳍原鲌(C. erythropterus)体重与体维关系.结果表明,多元回归方程能全面地反映不同体维对鱼类体重的影响,体重与体侧面积体厚的回归方程较适宜.其体重(W)与体侧面积(A)及体厚(T)的幂函数关系式分别是,翘嘴鲌:W=4.05051×10-3A0.66260T1.41994;蒙古鲌:W=3.18603×10-3A0.66845 T1.44376;达氏鲌:W=1.99310×10-3A0.70982T1.47305;红鳍原鲌:W=3.58823×10-3A0.63253T1.49465. 相似文献
14.
The source parameters of the Bohai Sea earthquake, July 18, 1969 and Yongshan, Yunnan earthquake, May 11, 1974 were determined
by full — wave theory synthetic seismograms of teleseismic P waves. P+pP+sP wereform were calculated with WKBJ approximation
and real integral paths. One — dimensional unilateral, finite propagation source was also considered. By trail — and — error
in comparing the theoretical seismograms with the observational ones of WWSSN stations, the source parameters were obtained
as follow: for Bohai earthquake, φ=195°, δ=85°, λ=65°,M
o=0.9×1019Nm,L=59.9km.V
R=3.5km/s, ∧
R
=160°; for Yongshan earthquake, φ=240°, δ=80°, ∧=150°,M
o=1.3×1018Nm,L=48.8km,V
R=3km/s, ∧
R
=−10°, where φ is strike, δ dip angle, λ slip angle,M
o seismic moment,L rupture length,V
R rupture propagation speed. As III type fractures the faulting propagated along the fault planes, and ∧
R
is the angle from the strike to the propagation direction. Yongshan earthquake showed complexity in its focal process, having
four sub—ruptures during the first 60 seconds.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 1–8, 1991. 相似文献
15.
This study investigates the influence of Ca2+ and Mg2+ on the removal of F? by magnesium potassium phosphate (MPP) from water. The kinetic experiments reveal that the F? concentration decreased from 3.5 to 3.31 mg L?1 in a single (F?) system and to 1.45 mg L?1 in a ternary system (F?, Ca2+, and Mg2+) after 1 min, respectively. Thus, the F? removal efficiencies are found to increase by about 53% with the co‐active effect of Ca2+ and Mg2+ in the solution. Moreover, Ca2+ and Mg2+ are almost completely removed in the F?, Ca2+, and Mg2+ system. According to the pseudo‐first‐order modeling, the rate constants k for F?, Ca2+, and Mg2+ are 0.00348, 0.0106, and 0.0159 min?1 respectively; thus, Mg2+ > Ca2+ > F?. In the ternary system, the removal efficiencies are 53.29–66.03% for F?, 99.99–100% for Ca2+, and 87.21–95.19% for Mg2+ with initial pH 5–10. The removal efficiencies of F? increases with increases in initial concentrations of F?, Ca2+, and Mg2+. The removal of F? is governed by two routes: 1) adsorption by electrostatic interactions and outer sphere surface complexation; 2) co‐precipitation with Ca3(PO4)2, CaHPO4, Mg3(PO4)2, and Mg(OH)2. 相似文献
16.
Burša Milan Raděj Karel Šima Zdislav True Scott A. Vatrt Viliam 《Studia Geophysica et Geodaetica》1997,41(3):203-216
The geopotential scale factor R
o
= GM/W
o
(the GM geocentric gravitational constant adopted) and/or geoidal potential Wo have been determined on the basis of the first year's (Oct 92 – Dec 93) ERS-1/TOPEX/POSEIDON altimeter data and of the POCM 4B sea surface topography model: R
o
°=(6 363 672.58°±0.05) m, W
o
°=(62 636 855.8°±0.05)m
2
s
–2
. The 2°–°3 cm uncertainty in the altimeter calibration limits the actual accuracy of the solution. Monitoring dW
o
/dt has been projected. 相似文献
17.
M. D. Trifunac S. S. Ivanov M. I. Todorovska E. I. Novikova A. A. Gladkov 《Soil Dynamics and Earthquake Engineering》1999,18(3):375
This article explores the possibility to measure deformations of building foundations from measurements of ambient noise and strong motion recordings. The case under study is a seven-storey hotel building in Van Nuys, California. It has been instrumented by strong motion accelerographs, and has recorded several earthquakes, including the 1971 San Fernando (ML=6.6, R=22 km), 1987 Whittier–Narrows (ML=5.9, R=41 km), 1992 Landers (ML=7.5, R=186 km), 1992 Big Bear (ML=6.5, R=149 km), and 1994 Northridge (ML=6.4, R=1.5 km) earthquake and its aftershocks (20 March: ML=5.2, R=1.2 km; 6 December, 1994: ML=4.3, R=11 km). It suffered minor structural damage in 1971 earthquake and extensive damage in 1994. Two detailed ambient vibration tests were performed following the Northridge earthquake, one before and the other one after the 20 March aftershock. These included measurements at a grid of points on the ground floor and in the parking lot surrounding the building, presented and analyzed in this article. The analysis shows that the foundation system, consisting of grade beams on friction piles, does not act as a “rigid body” but deforms during the passage of microtremor and therefore earthquake waves. For this geometrically and by design essentially symmetric building, the center of stiffness of the foundation system appears to have large eccentricity (this is seen both from the microtremor measurements and from the earthquake recordings). This eccentricity may have contributed to strong coupling of transverse and torsional responses, and to larger than expected torsional response, contributing to damage during the 1994 Northridge, earthquake. 相似文献
18.
In the present work, we built a mathematical model of polychlorinated biphenyl (PCB) bioaccumulation in Perna viridis, namely, a one-compartment model with a time dependent incorporation rate R (μg g−1 lipid per ppb water per day), with positive substrate cooperativity as the underlying physical mechanism. The temporal change of the PCB concentration Q (μg g−1 lipid) in the soft tissues of the mussel depends on the competition of the input rate RW and the output rate kQ, where W is the concentration of PCB in water (ppb water) and k is the elimination rate (per day). From our experimental data, k=0.181±0.017 d−1. The critical concentration in water Wc for positive substrate cooperativity was found to be 2.4 ppb. Below Wc, R is a constant. For a water concentration of 0.5 ppb Aroclor 1254, R=24.0±2.4 μg g−1 lipid ppb−1 d−1. Above Wc, positive substrate cooperativity comes into effect and R becomes a function of time and dependent on the concentration Q in a form R=γQ/(Q+δ). This is the case for a water concentration of 5 ppb Aroclor 1254, where γ=15.1 μg g−1 lipid ppb−1 d1 and δ≈200 μg g−1 lipid. From this model, the uptake is exponentially increasing when the PCB concentration in the mussel is small compared to 200 μg g−1 lipid, and hyperbolically increasing when the concentration is large compared to 200 μg g−1 lipid, which are consistent with the experimental data. The model is useful for understanding the true processes taking place during the bioaccumulation and for risk assessment with higher confidence. Future experimental data which challenge the present model are anticipated and in fact desirable for improvement and perfection of the model. 相似文献
19.
The Local-Magnitude scale actually in use at Vesuvius Observatory is basedon the measure of seismogram coda duration, and calibrated with data fromIrpinia aftershocks. A recent study on local seismic attenuation at Mt.Vesuvius reveals coda shapes highly different from those from Irpiniaaftershocks, and a very low quality factor, if compared to the average Qof the region, indicating the necessity of the revision of the Magnitudescale, in order to better compare the seismic energy associated to the localseismicity of Mt. Vesuvius to that of other active volcanoes. Being theseismic attenuation parameters known in the area, we could correct theseismic amplitudes for the path effect to obtain precise estimates of theamplitude level of the displacement spectrum. Hence we estimated theMoment-Magnitude, M
W, for a set of well recorded micro-earthquakes.To use the Richter formulaM
L =log10
A
max –log A0(R)we estimated the log Amplitude-Distance correction curve, - log A0(R),numerically synthesizing an S-wave-packet and letting it propagate in aearth medium with the same attenuation properties of those measured at Mt.Vesuvius. Then we synthesized the Wood-Anderson equivalent seismogram forthe same data set and used the distance correction in order to calculate theWood-Anderson Magnitude.This Magnitude scale was normalized in order to fit the Richter formulavalid for Southern California at a distance of 10 km, and resultsto be M
WA =log A + 1.34log(R) –1.10. The comparison of the Wood-Anderson scale with the Duration-Magnitude scalein routine use at Vesuvius Observatory indicates that care must be takenwhen the estimate of the Duration-Magnitude is carried out for smallearthquakes recorded at a site characterized by a high level of seismicnoise. 相似文献