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101.
长江靖江段沿岸似鳊生长及种群参数估算 总被引:2,自引:0,他引:2
2012年1月~2013年12月连续24个月在长江靖江段沿岸收集似鳊标本2 334尾,采用基于体长频率数据的ELEFAN I技术估算长江近口段沿岸似鳊的生长参数与种群参数。结果表明:似鳊体长(L,cm)与体质量(W,g)幂函数关系为:W=0.0182×L~(2.948)(r=0.9823,n=2334)。Von Bertalanffy生长方程描述的似鳊生长参数为:极限体长(L_∞)=19.25 cm,生长系数(K)=0.2/a,理论生长起点年龄(t_0)为-1.59 a,体质量的生长拐点年龄为3.55 a。采用Pauly的经验公式估算似鳊自然死亡系数(M)为0.556/a。由长度变换渔获曲线法估算出的似鳊总死亡系数(Z)为1.638/a,捕捞死亡系数(F)和开发率(E)分别为1.082/a和0.66/a。2012~2013年长江靖江段沿岸似鳊年均资源重量和资源数量分别为120.59 t和947.4万尾。经相关估算参数和相对单位补充渔获量分析得出,当前长江靖江段沿岸似鳊已处于过度捕捞状态。建议将沿岸水域禁渔期延长至9月(即4~9月),以实现似鳊资源的恢复和可持续发展。 相似文献
102.
Hemlock Woolly Adelgid (Adelges tsugae) is spreading across forests in eastern North America, causing mortality of eastern hemlock (Tsuga canadensis [L.] Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.). The loss of hemlock from riparian forests in Great Smoky Mountains National Park (GSMNP) may result in significant
physical, chemical, and biological alterations to stream environments. To assess the influence of riparian hemlock stands
on stream conditions and estimate possible impacts from hemlock loss in GSMNP, we paired hardwood- and hemlock-dominated streams
to examine differences in water temperature, nitrate concentrations, pH, discharge, and available photosynthetic light. We
used a Geographic Information System (GIS) to identify stream pairs that were similar in topography, geology, land use, and
disturbance history in order to isolate forest type as a variable. Differences between hemlock- and hardwood-dominated streams
could not be explained by dominant forest type alone as forest type yields no consistent signal on measured conditions of
headwater streams in GSMNP. The variability in the results indicate that other landscape variables, such as the influence
of understory Rhododendron species, may exert more control on stream conditions than canopy composition. The results of this study suggest that the
replacement of hemlock overstory with hardwood species will have minimal impact on long-term stream conditions, however disturbance
during the transition is likely to have significant impacts. Management of riparian forests undergoing hemlock decline should,
therefore, focus on facilitating a faster transition to hardwood-dominated stands to minimize long-term effects on water quality. 相似文献
103.
The effects of increasing Cu, Ni and Cr concentrations (0.5, 5, 10, 20 and 40 mg L−1) on microtubule organization and the viability of leaf cells of the seagrass Cymodocea nodosa for 13 consecutive days were investigated under laboratory conditions. Increased oblique microtubule orientation, microtubule depolymerization at the 5–40 mg L−1 Ni treatments after 3 d of exposure, and a complete microtubule depolymerization at all Ni treatments after 5 d were observed. Cu depolymerised microtubules after three to 7 d of exposure, while Cr caused an extensive microtubule bundling after 9 or 11 d of exposure, depending on metal dosage. Fluorescence intensity measurements further consolidated the above phenomena. Cell death, occurring at later time than microtubule disturbance, was also observed at all Cu and Ni treatments and at the 10–40 mg L−1 Cr treatments and adding to the above quantification of the number of dead cells clearly showed that only a portion of the cell population studied died. The data presented, being the first assessment of microtubule disturbance in seagrasses, indicate that microtubules in seagrass leaf cells could be used as a valuable and early marker of metal-induced stress in biomonitoring programmes. 相似文献
104.
Fisher WS Davis WP Quarles RL Patrick J Campbell JG Harris PS Hemmer BL Parsons M 《Environmental monitoring and assessment》2007,125(1-3):347-360
Coral reefs provide shoreline protection, biological diversity, fishery harvests, and tourism, all values that stem from the
physically-complex coral infrastructure. Stony corals (scleractinians) construct and maintain the reef through deposition
of calcium carbonate. Therefore, assessment of coral reefs requires at least some measurement endpoints that reflect the biological
and physical condition of stony corals. Most monitoring programs portray coral quantity as live coral cover, which is the
two-dimensional proportion of coral surface to sea floor viewed from above (planar view). The absence of the third dimension,
however, limits our ability to characterize coral reef value, physiology, health and sustainability. A three-dimensional (3D)
approach more realistically characterizes coral structure available as community habitat and, when combined with estimates
of live coral tissue, quantifies the amount of living coral available for photosynthesis, growth and reproduction. A rapid
coral survey procedure that coupled 3D coral quantification with more traditional survey measurements was developed and tested
in the field. The survey procedure relied on only three underwater observations – species identification, colony size, and
proportion of live tissue – made on each colony in the transect. These observations generated a variety of metrics, including
several based on 3D colony surface area, that are relevant to reef management. 相似文献
105.
Persistent organic pollutants (POPs) in Caspian seals of unusual mortality event during 2000 and 2001 总被引:1,自引:0,他引:1
Kajiwara N Watanabe M Wilson S Eybatov T Mitrofanov IV Aubrey DG Khuraskin LS Miyazaki N Tanabe S 《Environmental pollution (Barking, Essex : 1987)》2008,152(2):431-442
Persistent organic pollutants including organochlorine pesticides, PCBs, and PCDDs/DFs were determined in the blubber of Caspian seals, which died during an outbreak of canine distemper virus in 2000 and 2001. DDTs were the predominant contaminants that ranged from 3.1 to 560 microg/g lipid. A negative correlation was observed between concentration of contaminants and blubber thickness. During spring, as the blubber layer becomes thin after breeding and moulting, seals may face higher risk due to the increased concentration of organochlorines in their bodies. TEQs in the blubber of Caspian seals (10-340 pg TEQ/g) were lower than those in seals from other locations, suggesting that toxic effects of these contaminants are a deal less in the present population and they are unlikely to be linked to mass mortality. The levels of PCBs and pesticides in Caspian seals, however, comparable to those in other aquatic mammals that have suffered from epizootics, might pose a risk of immunosuppression. 相似文献
106.
Analysis of the National Center for Health Statistics' Compressed Mortality File showed that between 1979 and 2004, natural events caused 21,491 deaths in the United States. During this 26-year period, there were 10,827 cold-related deaths and 5,279 heat-related deaths. Extreme cold or heat accounted for 75 per cent of the total number of deaths attributed to natural events— more than all of deaths resulting from lightning, storms and foods, and earth movements, such as earthquakes and landslides. Cold-related death rates were highest in the states of Alaska, Montana, New Mexico, and South Dakota, while heat-related deaths were highest in the states of Arizona, Missouri, and Arkansas. These deaths occurred more often among the elderly and black men. Other deaths were attributed to lightning (1,906), storms and foods (2,741), and earth movements (738). Most deaths associated with natural events are preventable and society can take action to decrease the morbidity and mortality connected with them. 相似文献
107.
B. H. King 《Behavioral ecology and sociobiology》2000,48(4):316-320
In the parasitoid wasp Spalangia endius more offspring and a greater proportion of daughters were oviposited in, and emerged from 0-day-old versus 3-day-old hosts.
Offspring that developed on the younger hosts (1) were larger at adulthood, (2) developed more quickly, (3) had higher survivorship
to adulthood, and (4) were more often able to chew their way out of the host. Sons and daughters did not differ in how host
age affected their size, development rate, or survivorship. The greater proportion of daughters from the younger hosts may
be adaptive, as described by the host quality model (a variant of the Trivers and Willard hypothesis). It is adaptive if greater
size or more rapid development has a more positive effect on a daughter’s than a son’s fitness and the positive effect is
large enough to compensate for sons being trapped disproportionately to daughters in the older hosts. Despite greater success
at drilling the younger hosts, mothers did not try to drill them sooner or more often. Having previously oviposited on the
older rather than the younger hosts had no detrimental effect on the mother’s subsequent longevity or offspring production.
Received: 8 March 2000 / Revised: 9 June 2000 / Accepted: 24 June 2000 相似文献
108.
Birth sex ratios were examined for ringtailed lemurs (Lemur catta) at the Duke University Primate Center. This population provides a long-term database of births under a variety of demographic
and management conditions, including two semi-freeranging groups between which males transfer freely and females defend stable
territorial boundaries. We examined three hypotheses usually considered in studies of primate sex ratio bias. The Trivers-Willard
hypothesis predicts that dominant females produce males, local resource competition at the population level (LRC-population)
predicts that the dispersing sex (males) will be overproduced in dense populations, and local resource competition among individuals
(LRC-individual) predicts that dominant females overproduce the philopatric sex (females). We also examined a fourth hypothesis,
local resource enhancement (LRE), which is usually subsumed under LRC-individual in studies of primate sex ratio evolution.
LRE predicts that under certain conditions, females will produce the sex that provides later cooperative benefits, such as
alliance support for within- or between-group competition. Our data provide support for LRE: females overproduce daughters
given prospects of new group formation, either through group fission or threatened expulsion of young mothers. Behavioral
data from Duke and also wild populations show that daughters serve mothers as important allies in this context and LRE effects
also have been documented in other mammals that experience similar group histories. Nonsignificant trends in the data supported
the LRC-population hypothesis, and we suggest that LRC interacts with LRE to explain offspring sex ratios in ringtailed lemurs.
Received: 27 August 1999 / Received in revised form: 6 March 2000 / Accepted: 18 March 2000 相似文献
109.
Heavy metal concentrations in plants and different harvestable parts: A soil-plant equilibrium model
Sebastián D. Guala Emma F. Covelo 《Environmental pollution (Barking, Essex : 1987)》2010,158(8):2659-2663
A mathematical interaction model, validated by experimental results, was developed to modeling the metal uptake by plants and induced growth decrease, by knowing metal in soils. The model relates the dynamics of the uptake of metals from soil to plants. Also, two types of relationships are tested: total and available metal content. The model successfully fitted the experimental data and made it possible to predict the threshold values of total mortality with a satisfactory approach. Data are taken from soils treated with Cd and Ni for ryegrass (Lolium perenne, L.) and oats (Avena sativa L.), respectively. Concentrations are measured in the aboveground biomass of plants. In the latter case, the concentration of metals in different parts of the plants (tillering, shooting and earing) is also modeled. At low concentrations, the effects of metals are moderate, and the dynamics appear to be linear. However, increasing concentrations show nonlinear behaviors. 相似文献
110.