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1.
研究了湛江沿海中华乌塘鳢个体生殖力及其与生物学指标的关系。结果表明 :个体绝对生殖力为 840 0~ 3 3 2 70粒 ,个体相对生殖力FL 为 5 67 6~ 1 83 3 2粒 /cm ,Fw为 1 5 5 6~ 482 7粒 /g ;个体绝对生殖力与体长、体重、空壳重、卵巢重呈直线相关 ,与年龄呈二次函数相关 ,与成熟系数和肥满度相关关系不显著 ;个体相对生殖力FL 与各生物学指标正相关 ,Fw除了与卵巢重、肥满度和年龄相关关系不显著外 ,其余均显著相关 相似文献
2.
The North Pacific has the world's largest groundfish fisheries, with a value in excess of $1 billion annually. The North Pacific also is home to the largest population of Steller sea lions (SSL), an ancient species that is now endangered. Decline of the western stock of SSL in the 1970–1990s coincided with the US nationalization and exponential growth in the Gulf of Alaska and Bering Sea/Aleutian Islands groundfish fishery.The article treats five aspects of the competition between the fishery and protection of the endangered species. First, we analyze competition of interests in the use, management, and preservation of the North Pacific commons, including offshore and near-shore fisheries, environmental organizations, governments (federal, state, and local), and the scientific community. Second, the article compares and contrasts provisions of the National Environmental Policy Act, the Marine Mammal Protection Act, the Endangered Species Act, and the Magnuson–Stevens Act (as amended in 1996 by the Sustainable Fisheries Act).Third, we examine the regulatory environment with a focus on the National Marine Fisheries Service (NMFS) and its relationship to the North Pacific Fishery Management Council. We illustrate how NMFS establishes fishery management plans and the methods, such as crafting biological opinions and environmental-impact-statements, it uses to resolve conflicts. Fourth, we investigate how the dual pressures on the agency—to increase fisheries production for the benefit of the industry and to preserve endangered marine species—have affected its culture (behavioral norms and operational codes). Then, the article explains agency changes in terms of crises, competition among affected interests, and development of new scientific knowledge.The article concludes by drawing lessons from the SSL controversy in the North Pacific which may pertain to national and global biodiversity conflicts. These concern the role of law in biodiversity protection, the role of science, and agency capacity for change. 相似文献
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Macro-ecological theories relating species richness, abundance, range size, biological traits and environmental tolerance have rarely been tested in marine soft-sediments, despite the spatial extent of these habitats and the inherent richness of resident communities. This study examines the contribution of rare species to marine soft-sediment communities from New Zealand, focussing on the relationships of range size with abundance, environment, habitat diversity and life history traits. 54% of the 351 species sampled exhibited restricted ranges (found at ≤ 2 sites). In contrast to many terrestrial systems, we observed only a weak positive relationship between abundance and frequency of occurrence. Restricted-range species were not randomly distributed, with their distribution related to habitat characteristics, suggesting an important link between habitat diversity and rarity. They exhibited a similar range of traits to the total observed species pool, suggesting that they are not only important to biodiversity but could play a role in stability. Restricted range species were generally not small and this, together with the number of different biological traits represented, suggests that rare species are important to the functioning of marine systems. Thus, our results highlight the importance of considering rare species in habitat-based approaches to conservation. 相似文献
6.
Intense studies of upper and deep ocean processes were carried out in the Northwestern Indian Ocean (Arabian Sea) within the framework of JGOFS and related projects in order to improve our understanding of the marine carbon cycle and the ocean’s role as a reservoir for atmospheric CO2. The results show a pronounced monsoon-driven seasonality with enhanced organic carbon fluxes into the deep-sea during the SW Monsoon and during the early and late NE Monsoon north of 10°N. The productivity is mainly regulated by inputs of nutrients from subsurface waters into the euphotic zone via upwelling and mixed layer-deepening. Deep mixing introduces light limitation by carrying photoautotrophic organisms below the euphotic zone during the peak of the NE Monsoon. Nevertheless, deep mixing and strong upwelling during the SW Monsoon provide an ecological advantage for diatoms over other photoautotrophic organisms by increasing the silica concentrations in the euphotic zone. When silica concentrations fall below 2 μmol l−1, diatoms lose their dominance in the plankton community. During diatom-dominated blooms, the biological pathway of uptake of CO2 (the biological pump) appears to be more efficient than during blooms of other organisms, as indicated by organic carbon to carbonate carbon (rain) ratios. Due to the seasonal alternation of diatom and non-diatom dominated exports, spatial variations of the annual mean rain ratios are hardly discernible along the main JGOFS transect.Data-based estimates of the annual mean impact of the biological pump on the fCO2 in the surface water suggest that the biological pump reduces the increase of fCO2 in the surface water caused by intrusion of CO2-enriched subsurface water by 50–70%. The remaining 30 to 50% are attributed to CO2 emissions into the atmosphere. Rain ratios up to 60% higher in river-influenced areas off Pakistan and in the Bay of Bengal than in the open Arabian Sea imply that riverine silica inputs can further enhance the impact of the biological pump on the fCO2 in the surface water by supporting diatom blooms. Consequently, it is assumed that reduced river discharges caused by the damming of major rivers increase CO2 emission by lowering silica inputs to the Arabian Sea; this mechanism probably operates in other regions of the world ocean also. 相似文献
7.
Soil crust lichens can be the dominant vegetation in arid lands, yet their importance as habitat to secondary producers is relatively unknown. This study examines the distribution of arthropod communities in the northern Namib Desert to evaluate whether a lichen-rich area is more or less productive than adjacent habitats in terms of the consumers each supports. Arthropods are diverse and highly endemic in the Namib Desert and lichens dominate this desert's extensive gravel plains. We sampled lichen-rich, dwarf shrub, and unvegetated sites and found distinct arthropod assemblages in the lichen-dominated sites, including species unique to lichen sites. Arthropod assemblages in two of the lichen sites were similar to those found in the dwarf shrub site. In a canonical correspondence analysis, crustose lichens and overall lichen cover were key in driving the variance in arthropod assemblages within the lichen sites. Furthermore, lichen morphotypes, overall lichen cover and species richness, were significantly correlated with the representation of arthropod subgroups and arthropod species richness. These findings provide evidence that lichen-dominated soil crusts in the Namib Desert are important supporters of secondary production, warranting more in-depth studies into the ecology and conservation of this lichen-rich habitat in warm deserts. 相似文献
8.
Major biological parameters of four permanent (Lake Colac, Modewarre, Bolac and Tooliorook), shallow and slightly saline lakes in the volcanic plains of western Victoria, Australia recorded bi-monthly between November 1999–September 2001 are described. Chlorophyll a concentration ranged from 3–29 μg l−1 with peaks in autumn. Phytoplankton taxa recorded were diverse, with Chlorophyta and Bacillariophyta being common. Cyanobacterial blooms were recorded mostly in summer. Zooplankton abundance in the lakes ranged from 12–368 individuals per litre. Rotifera dominated Lake Bolac, Copepoda dominated Lake Modewarre and they co-dominated Lake Colac and Tooliorook. Zooplankton interactions with phytoplankton suggest that simple predator-prey relationships cannot fully explain the trends exhibited and that a more complex model was acting to regulate algal biomass. A decline in the abundance of zooplankton in summer in Lake Modewarre was attributed to predation by high number of exotic larval carp at that time of the year. A total of 25 benthic macroinvertebrate taxa were recorded from Lake Colac, 30 from Modewarre, 22 from Bolac and 35 from Tooliorook. Twenty-one of the 45 taxa identified occurred in at least three lakes. Nine of the 12 taxa that occurred in only one lake were from Lake Tooliorook. Simpson's diversity index was low in Lake Bolac when compared to other three lakes. Lake Modewarre had more benthic individuals (3246 Ind m−2) than other three lakes (range 624–1397 Ind m−2). The combined contribution of Ostracoda, Amphipoda and Gastropoda dominated the benthos in all the lakes throughout the study period. Macroinvertebrate taxa richness was higher in the present study lakes than recorded from the lakes in the region. Frequency of sampling and number of sampling sites seemed more important in determining species richness than the size and shallowness of the lakes. 相似文献
9.
With the acceleration of industrialization, coal- burning atmospheric pollution is getting more and more serious in many regions in China. However, there are only about ten odd years literature records about pollution in some large and mid-sized cities, where the atmosphere has perhaps been polluted for several decades, and therefore it is difficult to know the process and characteristic of pollution, and diffi-cult to evaluate its damage to environment. Lacustrine sediment, a natural record w… 相似文献
10.
海洋碳循环模式的进展 总被引:2,自引:0,他引:2
本文综述了两类近年来国外使用的海洋碳循环数值模式.一类是国外通常使用的比较简单的箱模式;另一类是基于大洋环流模式的三维无机碳循环模式,以及在该模式的基础上引进了海洋生物群作用的海洋碳循环模式.后者是目前比较完整的模式,也是本文重点介绍的内容. 相似文献