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1.
Frank J. Mazzotti 《Estuaries and Coasts》1999,22(2):552-561
The American crocodile was declared endangered in the United States in 1975. At that time 75% of the remaining crocodile nests were in Everglades National Park, in Florida Bay. In 1980, the National Park Service established a crocodile sanctuary in northeastern Florida Bay to protect nesting and nursery habitat. In 1985, a monitoring program, focused on nesting, growth, and survival, was established to evaluate the effects of modified water deliveries on crocodiles in Florida Bay. The number and range of crocodile nests increased between 1970 and 1995, but nesting success decreased slightly. Nests on artificial substrates in the Greater Flamingo-Cape Sable area accounted for most of the increase in nests. Nests on artificial substrates were more prone to predation by raccoons. At least 1.5% of marked hatchlings survived for more than 12 mo, and growth rates were variable. Detailed information on growth and survival of crocodiles is still lacking. It is no longer a question of whether crocodiles with survive in Florida Bay, but how ecosystem restoration and management can be applied to improve conditions for crocodiles. 相似文献
2.
JoAnn McGregor 《Geoforum》2005,36(3):353-369
This article is about the politics of conservation in postcolonial Southern Africa. It focuses on the process and consequences of redefining the Nile crocodile as an endangered species and explores the linked local and international, commercial and conservationist interests that allowed the animal to re-establish itself in state-protected waterways in colonial and postcolonial contexts. It investigates the effects of the animal’s successful re-accommodation by examining conflicts between crocodiles and the fishing communities sharing space on Lake Kariba, Zimbabwe. Fishermen’s hostile representations of the animal emphasize competition for fish, harassment, fear, loss of assets and loss of life. Their fear of crocodiles is heightened by the animal’s entanglement in local social life, through its association with witchcraft. The article emphasizes the importance of considering both hegemonic and marginalized ideas about animals in the light of the material interactions, relations of power and historical contexts that shape them. Understanding the attitudes and circumstances of the local communities who bear the physical and economic costs of living with dangerous animals is important--it threatens the future of conservation programmes and reveals the potential for significant abuses to accompany the conservation of wildlife in postcolonial contexts. 相似文献
3.
《Cretaceous Research》1988,9(4):379-389
Amargasuchus minor is described from the Early Cretaceous (Neocomian, of the La Amarga Formation of northwest Patagonia (Argentina). This species possesses a moderately high and narrow snout, strong festooning, a relatively large number of maxillary teeth and a well developed antorbital fenestra, and it lacks hypertrophied teeth, a combination of characters which suggests that it belongs to the crocodile family Trematochampsidae. Amargasuchus differs, however, from Trematochampsa in several respects. These include an almost straight lateral edge of the maxilla in dorsal aspect, a different distribution of the largest teeth, a longer snout, and laterally compressed alveoli. The new material supports a Gondwanan origin of the Trematochampsidae and agrees with a new phylogenetic hypothesis which considers trematochampsids to be the ancestral group of certain lineages of ziphodont mesosuschian crocodiles. 相似文献
4.
The John Martin Reservoir tracksites from the Dakota Group of Bent County, in southeastern Colorado form part of the mid Cretaceous Dinosaur Freeway characterized by abundant ornithopod footprints (Caririchnium). Over 350 tracks (331 Caririchnium, 1 Magnoavipes, 22 crocodiles, and a few pterosaurs) were discovered at 10 new tracksites. All tracks were found as natural casts, including Caririchnium trackways that were still in-situ, parallel and regularly spaced, suggesting gregarious behavior. Most crocodile tracks are swimming tracks that consist of three or four scratch marks also with parallel orientations in many cases. A few pterosaur tracks consist of pes footprints and scratch marks suggesting swimming or floating activity in shallow water. This is the first pterosaur evidence from the Dakota Group. The Caririchnium size structure from John Martin Reservoir is consistent with the size structure tendency of the whole Dinosaur Freeway, which shows larger track size in the north. This tendency could be interpreted as evidence for more than one ornithopod species spread out across the Dinosaur Freeway. The alternative, that there was one ornithopod species that migrated north and south seasonally is less likely. The John Martin paleoecosystem is interpreted from the track evidence as a well-vegetated coastal plain environment with many ornithopods and a few theropods on land, crocodiles in the water, and pterosaurs in the skies and on the water. 相似文献
5.
列举并尝试对比了非洲早白垩世脊椎动物化石的主要产地。晚侏罗世(坦桑尼亚的敦达古鲁基默里奇期提塘期)至白垩纪最早期(南非的阿尔戈阿盆地凡兰吟期)的组合中含有剑龙、腕龙和梁龙,到前阿普特期(欧特里沃期巴列姆期?)被另一组合所取代。这一更年轻的组合中含有重爪龙亚科棘龙类、大头鳄类鳄鱼Sarcosuchus以及大型禽龙,它们主要来自尼日尔(ElRhaz组和喀麦隆(Koum组),部分来自利比亚(Cabao组)和突尼斯(Douiret组),后两组中还含有鲨鱼Priohybodus ar ambourgi。阿普特期(?)至早阿尔必期组合中仍含有禽龙,但是棘龙科棘龙类取代了重爪龙亚科。早塞诺曼期组合(Bahariya,Kem Kem)以恐龙Spinosaurus、Carcharodonto saurus,鲨鱼(Onchopris tisnumidus)和鳄鱼(利比亚鳄类、无棘腔鳄类)为特征。由此可知,中非的一些原先被认为是早白垩世的地层(坦桑尼亚的Galula组、马拉维的含恐龙层)为晚白垩世。脊椎动物化石在非洲陆相地层的对比中具有重要作用。 相似文献
6.
7.
Kerry E. Flaherty Theodore S. Switzer Brent L. Winner Sean F. Keenan 《Estuaries and Coasts》2014,37(1):206-228
Reef fishes, such as gray snapper, support important recreational and commercial fisheries and use a variety of habitats throughout ontogeny. Gray snapper juveniles may be found in estuarine nursery areas, such as seagrass beds, or mangrove shorelines, while adults are most often found in deep channels and farther offshore, associated with hard-bottom habitats. Juvenile and subadult gray snapper were collected from 1996 through 2009 during long-term fishery-independent monitoring of several estuarine systems along the Gulf and Atlantic coasts of Florida. Indices of abundance and habitat suitability were constructed for gray snapper to determine size-specific relationships between abundance, habitat, and environmental conditions. Juvenile and subadult gray snapper were collected year-round only in the southernmost estuaries but were most common from July through December in all estuaries sampled. In addition to timing of estuarine occupancy, abundance varied with latitude; gray snapper were more frequently collected in warmer, southern estuaries. In general, gray snapper were most abundant in euhaline areas with a high percentage of submerged aquatic vegetation (SAV) and, in most cases, where overhanging shoreline vegetation was also present. Annual abundance varied over the sampling period, with some juvenile peaks in abundance translating to subadult peaks in subsequent years. Although strong correspondence between juvenile and subadult populations was not observed in all systems, long-term, broad-scale habitat selection patterns as described in this study are critical to more effectively assess populations of estuarine-dependent species. 相似文献
8.
黑龙江沿岸晚白垩世恐龙生物群化石产地的初步预测 总被引：1，自引：0，他引：1
根据对黑龙江沿岸孙吴、逊克和嘉荫保兴-炮台店一带晚白垩世地层与嘉荫乌拉嘎、龙骨山等含恐龙化石群的渔亮子组(K2y)等对比及在前三个地区已发现部分恐龙化石的线索,初步预测孙吴北部、逊克东南部和嘉荫保兴-炮台店等三地区可能为较大规模的恐龙化石群产地。预测区含恐龙化石的晚白垩世地层均属河流-湖泊相沉积,除恐龙外,尚可能发现叶肢介、介形类、鱼、龟鳖类、鳄、鸟类及被子植物等伴生化石。上述地区下伏于渔亮子组的太平林场组(K2t)和永安村组(K2yn)等地层,也有含恐龙化石的可能性。 相似文献
9.
Conservation efforts often neglect the importance of monitoring of protected areas, which is key to adaptively managing dynamic landscapes. In many developing countries, like Trinidad, protected areas are set aside as a result of an agreement with an international conservation organization, often resulting in inadequate planning and monitoring of the protected area. Monitoring of protected areas allows for an examination of the conservation scheme implemented and enables improved conservation decisions to be made. The research presented provides an example of the use of technology in monitoring conservation strategies in two protected wetlands, Caroni and Nariva, in Trinidad. Remote sensing and fragmentation analyses are used to quantify land cover change within these two protected wetlands. Results show that the classification of Caroni immediately identifies a shift towards anthropogenic land cover types, suggesting an increase in human activity within the park. This finding is further supported by the continuous measures used, such as decreases in mean NDVI and greenness values suggesting a decrease in the amount or health of the vegetation. While the classification of Nariva suggests a return to natural land covers, the continuous measures of land cover change indicate the opposite. Land cover change analyses are limited in Trinidad and in the Caribbean in general, partly due to satellite data availability, thus this research presents remote sensing and landscape fragmentation analyses as new tools for monitoring land cover change and conservation effectiveness in Trinidad. 相似文献
10.
Environmental conservation and the production of new territories: the example of French départements
Pech Pierre Dizière Sophie Gillet Anne-Gabrielle Mamder Julie Tichit Marion 《GeoJournal》2010,75(2):149-161
Very important initiatives have been taken and policies have been adopted in the European Union to protect areas of great
importance for threatened species and habitats. Protected areas differ broadly in terms of category, natural conditions and
administrative organisation, from international initiative such as Biosphere Reserves, European ones with Natura 2000 network
until the institution of national and regional protected areas. In France, the administrative subdivisions known as “départements” were created with the French Revolution in the end of the eighteenth century; in 1985 an original and autonomous procedure
to establish special protected areas, called “Sensitive Natural Spaces” (SNS) was devolved to them. The scope of this paper
is to present an overview of these devolved powers which enable French départements to create protected areas and to levy a departmental tax on sensitive natural spaces (DTSNS). We statistically studied some
parameters by multivariate methods in order to explain the choices of this policy by the départements. The huge variations in the way these powers are implemented prove the development of new environmental territories. 相似文献
11.
Seagrass meadows are often cited as important nursery areas for newly settled red drum even though many estuaries, such as Galveston Bay, Texas, support large numbers of red drum and have limited seagrass cover, suggesting the use of alternate nursery areas. We examined patterns of habitat use for newly settled red drum at six sampling areas in Galveston Bay; two areas had seagrass beds and four areas had no seagrass. We measured densities in different habitat types using epibenthic sleds and enclosure samplers. Peak recruitment of young red drum to the estuary occurred during September through December. Highest densities of new settlers were found in seagrass meadows (primarilyHalodule wrightii), but when seagrass was absent, the highest densities of red drum occurred along theSpartina alterniflora marsh edge interface. Densities were relatively low on nonvegetated bottom away from the marsh edge. We also examined density patterns in other habitat types at selected sampling areas and found no red drum within marsh vegetation away from the marsh edge interface (5 and 10 m into the marsh interior). Oyster reefCrassostrea virginica was sampled using lift nets, and we found no red drum using this habitat, although adjacent seagrass and marsh interface habitats were used. Even though red drum densities in marsh edge were low relative to seagrass, the large areal extent of marshes in the bay complex probably makes marsh edge the most important nursery habitat for red drum in Galveston Bay. 相似文献
12.
S. M. Azarkar H. Ahmadi N. Khorasani M. Karami 《International Journal of Environmental Science and Technology》2006,2(4):387-393
Animal species in desert habitats are taken into consideration because of their uniqueness and inherent value. However the added pressures from climate and human have made living conditions difficult and acute for them. Wind erosion is one of the common phenomena in desert areas; this phenomenon can affect biotic value of those areas. Climatic constraints along with human development in such areas result in enhancing the effect of wind erosion, and as a result, affect the value of animal habitats. Therefore, by estimating the rate of wind erosion in such areas, the capability of environment for providing appropriate conditions for animal species’ subsistence can also be estimated. The objective of this research is to find the relation between the rate of wind erosion and value of animal habitat in Sarakhs as a representative of Razavi Khorasan Province. This research has been carried out in four steps: a) Approximate identification of each animal habitat in the area. b) Estimating the wind erosion based on IRIFR model. c) Estimating the approximate value of each of the animal habitats in the area. d) Determining the correlation between the value of each animal habitat with the average rate of wind erosion in that habitat. Investigating the relation between the average rate of wind erosion and the value of animal habitats which indicates that there is a significant correlation between them, that is to say, effective factors in increasing the rate of wind erosion have affected the quality of animal habitats, and proportional to their intensity, decreased the value of habitat. 相似文献
13.
The Bauru Basin was one of the great Cretaceous desert basins of the world, evolved in arid zone called Southern Hot Arid Belt. Its paleobiological record consists mainly of dinosaurs, crocodiles and turtles. The Bauru Basin is an extensive region of the South American continent that includes parts of the southeast and south of Brazil, covering an area of 370,000 km2. It is an interior continental basin that developed as a result of subsidence of the central-southern part of the South-American Platform during the Late Cretaceous (Coniacian–Maastrichtian). This sag basin is filled by a sandy siliciclastic sequence with a preserved maximum thickness of 480 m, deposited in semiarid to desert conditions. Its basement consists of volcanic rocks (mainly basalts) of the Lower Cretaceous (Hauterivian) Serra Geral basalt flows, of the Paraná-Etendeka Continental Flood Basalt Province. The sag basin was filled by an essentially siliciclastic psammitic sequence. In lithostratigraphic terms the sequence consists of the Caiuá and Bauru groups. The northern and northeastern edges of the basin provide a record of more proximal original deposits, such as associations of conglomeratic sand facies from alluvial fans, lakes, and intertwined distributary river systems. The progressive basin filling led to the burial of the basaltic substrate by extensive blanket sand sheets, associated with deposits of small dunes and small shallow lakes that retained mud (such as loess). Also in this intermediate context between the edges (more humid) and the interior (dry), wide sand sheet areas crossed by unconfined desert rivers (wadis) occurred. In the central axis of the elliptical basin a regional drainage system formed, flowing from northeast to southwest between the edges of the basin and the hot and dry inner periphery of the Caiuá desert (southwest). Life in the Bauru Basin flourished most in the areas with the greatest water availability, in which dinosaurs, crocodiles, turtles, fish, amphibians, molluscs, crustaceans, and charophyte algae lived. The fossil record mainly consists of transported bones and other skeletal fragments. In the northeastern and eastern marginal regions fossils are found in marginal alluvial fan deposits, broad plains of braided streams and ephemeral alkaline water lakes. In the basin interior the fossil record is related to deposits in sand sheets with braided streams, small dunes, and shallow lakes. In the great Caiuá inner desert a few smaller animals could survive (small reptiles and early mammals), sometimes leaving their footprints in dune foreset deposits. The aim of this article is to present and link the basin sedimentary evolution, palaeoecological features and palaeontological record. 相似文献
14.
The identification and protection of essential habitats for early life stages of fishes are necessary to sustain fish stocks.
Essential fish habitat for early life stages may be defined as areas where fish densities, growth, survival, or production
rates are relatively high. To identify critical habitats for young-of-year (YOY) alewives (Alosa pseud oharengus) in Lake Michigan, we integrated bioenergetics models with GIS (Geographic Information Systems) to generate spatially explicit
estimates of potential population production (an index of habitat quality). These estimates were based upon YOY alewife bioenergetic
growth rate potential and their salmonine predators’ consumptive demand. We compared estimates of potential population production
to YOY alewife yield (an index of habitat importance). Our analysis suggested that during 1994–1995, YOY alewife habitat quality
and yield varied widely throughout Lake Michigan. Spatial patterns of alewife yield were not significantly correlated to habitat
quality. Various mechanisms (e.g., predator migrations, lake circulation patterns, alternative strategies) may preclude YOY
alewives from concentrating in areas of high habitat quality in Lake Michigan. 相似文献
15.
Christopher N. Rooper Donald R. Gunderson David A. Armstrong 《Estuaries and Coasts》2003,26(4):1142-1154
English sole (Pleuronectes vetulus) is one of a few commercially important marine fishes on the Pacific coast of North America that use estuarine areas as nurseries for juvenile stages. Trawl surveys of four United States Pacific Northwest estuaries were conducted to determine spatial patterns of juvenile English sole residence in estuaries during 1998–2000. Additional data from 1983–1988 were also analyzed. Two size classes of juvenile English sole were identified during surveys, with densities of small (Total length [TL] <50 mm) sole ranging from 0 to 11,300 fish ha?1 across all sites, and densities of large (TL 50–150 mm) sole ranging from 0 to 33,000 fish ha?1 across all sites. Principal components analysis of static habitat data collected at each trawl survey site was used to define habitat types within each estuary, and discriminant function analysis was used to test the resulting classification scheme. Both small and large cohort English sole used lower side channel locations at significantly higher densities than other estuarine areas. Small English sole also showed significant relationships with both bottom temperature and depth. These patterns in habitat use were consistent across all estuaries and indicate that English sole used shallow depth areas surrounded by extensive tidal flats, where temperatures were optimal for growth. The analysis also suggested a carrying capacity may exist for large English sole in nursery estuaries. 相似文献
16.
Mark Bonta 《Geoforum》2005,36(1):95-112
Neotropical cloud forests have been locked away in protected areas that conservationists seek to fashion into spaces exclusively for “Nature,” but they often cannot do so because of the pressure of migrant agriculture, among other factors. The author documents the case of a protected area in Honduras that, while it fails to evolve into an idealized “conservation space,” nevertheless undergoes transformations until it becomes accepted by local actors as a space that provides protection for marginalized groups under threat from a hydroelectric project that seeks to dislodge them. A Deleuzian theoretical approach loosely drawing from complexity theory is utilized to explain the process whereby diverse and conflicting land-use spatialities come to embrace an alien and imposed national park and in the process ally with each other against a perceived greater threat from the outside. The author shows the transformative potentials of protected areas as allies, rather than enemies, of spatial justice movements currently confronting the challenges of “regional economic integration” initiatives such as the Central American Free Trade Agreement. 相似文献
17.
Jean-Michel Lefèvre 《Natural Hazards》2009,49(2):361-370
Long and high swells are dangerous for many islands located in the Tropics because they can generate large breakers and long
run up associated with large set up when reaching the coast. Most of the time those islands do not experience large waves
especially in usually protected areas, for instance, by coral reefs or wind protected. Long waves have the ability to reach
such areas, thanks to wave set up, shoaling and bottom refraction. This article describes an example of such high swell events
and its impact on the islands. The buoy network used by the French National Weather Service and all available satellite observations
related to waves are presented together with numerical sea-state models used to issue early warnings. 相似文献
18.
Tropical coastal seascapes are biodiverse and highly productive systems composed of an interacting mix of habitats. They provide crucial ecosystem services that support people’s livelihoods, yet key components of these seascapes remain unstudied. We know little about the deep (>2 m) subtidal areas of tropical estuaries, because, due to gear restrictions, there have been no detailed studies of the habitats they contain and the fish that use them. Consequently, potentially important functions and linkages with surrounding habitats remain unknown. Using unbaited videos, an approach capable of sampling the full breadth of benthic habitats and whole fish assemblages, we investigated patterns of fish occupancy of the deep subtidal habitats (2–20 m) in one of Australia’s largest tropical estuaries. We identified 19 taxa not previously recorded from estuaries of tropical eastern Australia, along with 36 previously identified estuary taxa. Three recognisable fish assemblages were associated with distinct benthic habitat types: open bottom fine sediment, seagrass and structurally complex rocky areas. In deep water, habitats often overlooked in shallow water become important, and there are sharp differences in habitat function. Deep subtidal habitats are potentially an important zone for direct interaction between estuary and marine fauna, with a range of consequences for intertidal habitat use and nursery ground functioning. The interface between marine areas and the shallow-water estuary may be richer and more complex than previously recognised. 相似文献
19.
A study was conducted to define winter distribution patterns of blue crabs,Callinectes sapidus, in the lower Chesapeake Bay and to relate these patterns to environmental variation. During February 1986 a stratified random survey was conducted to examine the distribution of blue crabs with respect to three major habitat types: 1) high energy, wave- and tide-dominated, spits and shoals; 2) moderate energy, tide-dominated basins; and 3) variable energy, tide-dominated or quiescent channels (natural or cut). Each major habitat type was further stratified on the basis of location (to account for possible salinity effects), resulting in a total of 17 habitat-stratum combinations. Blue crabs exhibited significant differences in abundance among habitats. Crabs were most abundant in the basin habitat and least abundant in the shoal and spit habitat. A posteriori evaluations of abundance patterns in relation to sediment type and depth showed that crabs were significantly more abundant where sediments contained between 41 and 60% sand and at depths exceeding 9 m. The sampled population of blue crabs was dominated by mature females. There were no significant differences in crab sex ratios between habitats, but significant differences between two fixed sites sampled through the winter showed that there were proportionately more male crabs at the western site than there were at the eastern site. The observed patterns indicate that some differential habitat utilization occurs and that overwintering female crabs are found preferentially in areas characterized by moderate energy regimes and fine, but sandy sediments. 相似文献
20.
Future development and climate change pose potentially serious threats to estuarine fish populations around the world. We
examined how habitat suitability for delta smelt (Hypomesus transpacificus), a state and federally protected species, might be affected by changes in outflow in the San Francisco Estuary due to future
development and climate change. Forty years of sampling data collected during fall from 1967 to 2008 were examined to define
abiotic habitat suitability for delta smelt as a function of salinity and water transparency, and to describe long-term trends
in habitat conditions. The annual habitat index we developed, which incorporated both quantity and quality of habitat, decreased
by 78% over the study period. Future habitat index values under seven different development and climate change scenarios,
representing a range of drier and wetter possibilities, were predicted using a model which related estuarine outflow to the
habitat index. The results suggested that each of the scenarios would generally lead to further declines in delta smelt habitat
across all water year types. Recovery targets for delta smelt will be difficult to attain if the modeled habitat conditions
are realized. 相似文献