首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Results of analyses of stomach and intestinal contents from hooded ( Cystophora cristata ) and harp ( Phoca groenlandica ) seals captured in the pack ice belt of the Greenland Sea in summer (July-August) in 2000 and winter (February-March) in 2001 revealed that the diet of both species were comprised of relatively few prey taxa. Pelagic amphipods of the genus Parathemisto , the squid Gonatus fabricii , polar cod ( Boreogadus saida ) and capelin ( Mallotus villosus ) constituted 63-99% of the observed diet biomass in both seal species, irrespective of sampling period, but their relative contribution to the diet varied both with species and sampling period/area. For hooded seals, G. fabricii and capelin were the dominant food items in winter 2001, but the summer 2000 diet comprised a mixture of this squid and polar cod. Parathemisto was most important for the harp seals during summer 2000; in winter 2001 the contribution from krill and capelin were comparable to that of Parathemisto . Multivariate analyses revealed differences in the intestinal contents of hooded and harp seals in areas where the two species' occurrence spatially overlapped. Different foraging depths of the two species may have contributed to the observed differences in diets.  相似文献   

2.
Fatty acid profiles and lipid biomarkers from 20 harp seals were used to investigate the foraging ecology of harp seals and the transfer of energy through the Franz Josef Land-Novaya Zemlya food chain. High levels of the Calanus fatty acid trophic markers (FATMs) 20:1(n-9) (mean 14.6%) and 22:1(n-11) (mean 6.5%), together with the typical dinoflagellate FATMs 22:6(n-3) (mean 6.5%) and C18PUFA (mean 5.5%), were found in blubber samples. Based on the analyses of the fatty acid profiles separated by principal component analysis, we confirmed the importance of polar cod ( Boreogadus saida ) and the pelagic amphipod Themisto libellula in the diet of harp seal. The high levels of 22:6(n-3), C18PUFA and C20 and C22 FATMs show that the harp seal lipids mainly originate from dinoflagellates consumed by Calanus copepods.  相似文献   

3.
An adult harp seal, caught by accident in a gill net during the peak of the seal invasions along the northern coasts of Norway (1986/87), was found to have eaten 2.466 kg of stones with masses up to 265 g. Different theories to why harp seals on occasion deliberately eat stones, with particular emphasis on the hypothesis that these may aid in the physical breakdown of fish flesh and hard fish bones, are discussed.  相似文献   

4.
We have employed a model for the energy balance of seals to estimate the energy consumption and energy expenditure of ringed seals throughout the year, using biological and physical parameters as input. Data on growth and seasonal changes in body mass and fat content "drives" the seasonal dynamics of the model output. The energy requirements for lactation and activity are based on data from earlier published studies. The analysis suggests that the food intake of ringed seals is highly seasonal. In adult males it is low during the periods of territory defense, mating and moulting from March to June. During this period the seals lose body mass, mainly as fat. The model predicts that lactating females increase their food intake to some extent during the approximately six-week lactation period. After the ice breakup, food intake increases in both sexes, partly as a result of increasing maintenance energy requirements, and partly because the body fat stores are rebuilt in late summer and autumn. The over-all energy requirements of the ringed seal appear to be basically similar to those of terrestrial mammals.  相似文献   

5.
Estimates of energetic demands for carnivore species can be valuable for estimating their annual prey requirements and thus, their potential impact on prey populations. This is the case for the coyote (Canis latrans) which has a ubiquitous distribution and preys on a wide variety of wild and domestic prey species. We took data on daily activity of coyotes and with standard energy models, estimated the daily field metabolic rate (FMR) of adult male and female coyotes in the Great Basin desert of the western United States. We then calculated the total annual energy demand and from this, extrapolated annual prey needs for lagomorph and rodent-sized prey. Daily FMR of male coyotes in the Great Basin desert averaged 1170.1 kcal±29.1, S.E. (n=11) and was significantly higher than 988.6 kcal±44.3 (n=8) for females (p=0.002). The highest reproductive cost for females was lactation (1441.1 kcal/day above FMR). Males and females need to consume 192 and 162 lagomorphs, or 3681 and 3110 rodents/year, respectively. For reproduction, females should consume 37 more lagomorphs or 700 more rodents per year. We concluded that preference for lagomorphs by coyotes reflects the most reasonable energy return on their hunting investment.  相似文献   

6.
The distributional patterns of Barents Sea harp seals (Phoca groenlandica) throughout the year are presented based on existing literature and recent Norwegian and Russian field observations. The harp seals breed in February-March in the White Sea. Moulting occurs during April to June in the White Sea and southern Barents Sea. Feeding.behaviour is closely related to the configuration and localisation of the drifting sea-ice during summer and autumn (June-October) when the seals follow the receding ice edge, retiring gradually northwards and northeastwards in the Barents Sea. The southward movement of the population in autumn probably takes place in November prior to the advance of the ice edge, and is likely related to food-search. Apparently, most Barents Sea harp seals seems to concentrate at the southern end of their range in winter and spring.  相似文献   

7.
A total of 284 ringed seals (Phoca hispida) were sampled to determine their diet in the spring of 1981 and 1982. Few seals contained identifiable stomach contents. No significant age-or sex-related differences in choice of prey were found. It seems that in spring northwestern Spitsbergen ringed seals prey upon arctic cod (Boreogadus saida) , decapods and larger amphipods.? Diet, ringed seal, Svalbard .  相似文献   

8.
中国食物供给能力分析   总被引：9，自引：0，他引：9  
王情  岳天祥  卢毅敏  杜正平  辛晓平 《地理学报》2010,65(10):1229-1240
从中国各类型生态系统(农田、草地、水域) 的实际的食物生产能力出发,结合进出口产品中的食物部分,得出全国实际的食物供给能力,根据食物营养成分表中的转化率,将各类食物折算成人类生存所需的3 大营养成分(热量、蛋白质、脂肪) 的产量来表示,并利用ArcGIS 进行草地和农田食物供给的空间分析。以2004 年为例,中国实际食物供给能力为：热量1.601×1015 kcal,蛋白质6.163×107 t,脂肪2.717×107 t。其中,中国内陆生态系统实际可供给热量1.454×1015 kcal,蛋白质4.996×107 t,脂肪2.074×107 t,分别达到了陆地生态系统生产潜力的32.46%、38.33 %和41.12%,内陆生态系统食物供给还有较大的增长余地。在小康水平下,中国的食物热量、蛋白质、脂肪分别可以供养人口19.12 亿,20.84 亿和11.03 亿人,按照2010 年营养目标和2020 年全面小康目标,热量和蛋白质的供给已经较为充足,而脂肪的供给有所不足,今后需要注重油脂作物的种植和生产。结果还表明：中国的食物供给能力中,农田占据了绝大部分,不过比例有下降的趋势,从1998 年的84.66%,下降到2004 年的74.72%;草地和水域生态系统所提供的食物所占比例分别为4.83%~5.80%、6.02%~7.51%,波动较小;净进口食物所占比例逐年增长,1998 年仅为4.04%,2004 年增加到13.82%。通过平衡模型计算,在温饱、小康、富裕水平下,2004 年中国可以供养的人口分别为：15.34 亿,15.00 亿和14.11 亿,这表明,如果能够优化种植结构,合理配置植物性食物向动物性食物转化比例,均衡营养消费结构,中国实际食物供给较为充足。  相似文献   

9.
We examined the stability of fast ice areas in western and northern Spitsbergen, the area north of Nordaustlandet, the bays and sounds of Hinlopen Stretet and the large area in the northern part of Storfjorden. NOAA satellite imagery from 1974 and 1988 and NOAA (AVHRR) imagery from 1980-87 were used to determine the dates of freeze-up and break-up. The number of days of fast ice present before the nominal birth date of ringed seal pups were computed for all major bays and fjords. Ice thickness was then computed from these data. Known prime breeding habitat in Svalbard is found in areas near glacier fronts in protected fjords and bays, where densities of birth lairs are 5.46 km−2, corresponding to a ringed seal female density of 2.6 km−2. Most of the ringed seal breeding habitat in Svalbard, however, consists of flat fjord ice where snow accumulation is rarely deep enough to permit birth lair construction. In these areas pups are often born in the open. Based on breathing hole densities, the density of adult females in the flat ice areas in the breeding period was estimated to 0.98 km−2. A preliminary estimate is that approximately 19,500 pups could be born annually in the fast ice of Svalbard. Annual recruitment could be quite variable given the unpredictable nature of the fast ice areas and the high predation mortality on newborn pups. Discrepancies between our calculated ringed seal production and numbers of seals required to feed the large polar bear population in the area signal cause for management concern.  相似文献   

10.
Inuit hunting techniques used to catch ringed seals ( Phoca hispida ) were observed April-June 1993 on the land-fast ice of Admiralty Inlet, Nunavut, and adjoining fjords and bays. In addition, a survey of hunting techniques and knowledge of ringed seal biology and behaviour was conducted in the community of Arctic Bay (Ikpiarjuk), Nunavut, January-February 1994. A total of 246 seal structures were found in 31 days of hunting and 34 successful kills were observed. An experienced Inuk hunter found subnivean structures by sight, by walking on drifts and by probing snowdrifts with a harpoon ( unaaq ). Most structures were found using subtle visual cues. Breaking through the roof of a lair was the most common hunting technique observed in this study. Pups captured in this manner were subsequently used to lure the mother back into the breathing hole where she was harpooned. Ringed seals were also hunted by a number of other methods that have been described previously in the literature. Respondents in the hunter survey indicated that the ringed seal was the most important animal used by Arctic Bay Inuit. They also reported a variety of biological findings about ringed seals including: size differences among seals in different regions of the pack ice; that adult male ringed seals ( tiggak ) emitted a strong, mustelid-like odour from December until late May or early June. Hunters also reported that males were occasionally caught when coming to retrieve pups. All respondents reported seeing increasing frequencies of liver abnormalities in their ringed seal catches.  相似文献   

11.
The Ctenophora Mertensia ovum and Beroe cucumis , collected using both conventional sampling gear and scuba divers, were studied in the Barents Sea east of Bjørnøya and North Norway in spring 1987 and summer 1988. Among the gelatinous zooplankton, Mertensia ovum was the most consistently abundant copepod predator.
Feeding experiments were conducted to evaluate the predation rate of M. ovum in various trophic regimes. This ctenophore can take prey varying in size from small copepods to amphipods and krill, but gut-content analyses from field-collected specimens as well as experimental results showed that the main food source for adults was large-sized copepods (e.g. Calanus finmarchicus, C. glacialis, C. hyperboreus, Metridia longa ). The robust tentacle arrray of M. ovum makes this species effective as a predator on large prey. The high potential predation rate of this ctenophore relative to its estimated metabolic cost of only 1.7% of the body energy content d−1 suggests that M. ovum may be able to maintain a positive energy balance even in conditions of low prey abundance. It is suggested that a single exploitation of a zooplankton patch may provide energy for survival for a very long time.
The potential impact of M. ovum on Barents Sea copepod populations is estimated on the basis of the minimal observed average daily ration in experiments and from field data on gut contents. Using abundances of copepods for the area, and the actual predator biomass collected, it was estimated that an average of 0.7% of the copepod fauna per day could fall prey to this predator.  相似文献   

12.
Geografisk Tidsskrift—Danish Journal of Geography 110(2):245–259, 2010

This paper presents results of recent archaeological research at the site of Oakes Bay 1 (HeCg-08), on Dog Island, Labrador, dated from the late 17th to late 18th century. Analyses of faunal remains provide a means of reconstructing the site's subsistence economy. The site's inhabitants practiced a very consistent mode of hunting throughout this time period, depending heavily on adult ringed seals taken on the fast ice in winter and spring. Juvenile ringed seals, taken at the ice edge in the spring were a secondary resource. A lack of evidence for the hunting of harp seals in the fall and of ringed seal pups in late spring suggests that the site had a relatively short season of occupation. The consistent pattern of hunting through time suggests that the impacts of climatic variability on Inuit subsistence in the Nain region were relatively limited, moderated by their capacity for mobility on the sea ice rather than by whole scale changes in hunting practices and species choice. The Oakes Bay 1 site presents an example of a different subsistence economy than that seen at other recently examined sites in Labrador, suggesting that the impacts of the so-called Little Ice Age were not global or uniform.  相似文献   

13.
To understand the dynamics of small populations in arid environments, particularly in small insular ecosystems, it is crucial to understand the interactions between species inhabiting these environments. Here we investigate the interactions between lizards and scorpions in a small arid insular ecosystem in the Mediterranean. Experimental observations suggest that scorpions are regarded as prey by lizards. However, the response of lizards was sex-dependent, with males being more likely to attack scorpions than females. This can be associated with the larger body and head size, and bite forces in males, presumably making scorpions a profitable prey. Predation on lizards by scorpions has been also documented, suggesting a classic case of cross predation.  相似文献   

14.
Seal capacity estimation from subsurface pore pressures   总被引：1，自引：0，他引：1  
A cap rock's capacity to seal hydrocarbons depends on its wettability and the sizes of the pore throats within the interconnected pore system that the leaking hydrocarbons must penetrate. These critical pore throat sizes are often poorly constrained in hydrocarbon exploration, partly because measurements of pore throat sizes have not been performed, and partly because pore throat measurements on a few individual samples in the cap rock may not be representative for the seal capacity of the top seal as a whole. To the contrary, the presence of formation overpressure can normally be estimated in drilled exploration targets. The presence of overpressure in reservoirs testifies to small pore throats in the cap rocks, as large pore throats will result in sufficiently high cap rock permeability to bleed off the overpressure. We suggest a stepwise procedure that enables quantification of top seal capacities of overpressured traps, based on subsurface pressure information. This procedure starts with the estimation of cap rock permeabilities, which are consistent with observed overpressure gradients across the top seals. Knowledge of burial histories is essential for these estimations. Relationships between pore throat size and permeability from laboratory experiments are then applied to estimate critical pore throat diameters in cap rocks. These critical pore throat diameters, combined with information of the physical properties of the pore fluids, are then used to calculate membrane seal capacity of cap rocks. Estimates of top seal capacity based on this procedure are rather sensitive to the vertical fluid velocity, but they are also to some extent sensitive to inaccuracies of the pore throat/permeability relationship, overpressure gradient, interfacial tensions between pore fluids, hydrocarbon density and water viscosity values. Despite these uncertainties, applications of the above‐mentioned procedure demonstrated that the mere presence of reservoir overpressures testifies to sufficient membrane seal capacity of cap rocks for most geological histories. Exempt from this statement are basins with rapid and substantial sediment compaction in the recent past.  相似文献   

15.
Polar bear predation on ringed seals in the fast-ice of Hornsund, Svalbard   总被引：1，自引：0，他引：1  
Polar bear hunting success on ringed seals in subnivean lairs and basking on the fast ice, was studied in Hornsund, Svalbard. A few bears were observed while actually hunting, but in most cases bear tracks were followed by snowmobile to determine the outcome of hunts. Seal carcasses were classified from size and tooth annuli as pups, juveniles or adults. A total of 62 subnivean structures were entered by bears, with six seals killed. One of ten charges on basking seals resulted in a kill. Success rates of bears in Hornsund arc compared with results of studies in Canada and Svalbard. OHunting success, polar bear, predation, ringed seal  相似文献   

16.
南极海豹类生态学   总被引：1，自引：0，他引：1       下载免费PDF全文
描述了南极海豹的种类组成、资源量和种类状况等一般性生态学问题,着重讲述了这些海豹在研究全球变化中所起的作用等科学前沿问题;同时,就海豹研究在各国际组织中的地位阐述了意见。  相似文献   

17.
One explanation for recent declines in some Alaskan pinniped populations is that ecosystem changes may have reduced the availability of preferred prey. Part of our evaluation of this hypothesis involves the use of satellite-linked telemetry to study Steller sea lion (Eumelopias jubaius) and northern fur seal (Callorhinus ursinus) foraging. Data on dives (depth and duration) and water temperatures are collected by satellite-linked time-depth recorders (SLTDR) glued to the backs of sea lions and fur seals. These data are then summarized and stored for later transmission. Data are relayed back to land through NOAA Tiros-series satellites and are processed by Service-Argos (a U.S.-French consortium). These transmissions are also used to calculate at-sea and on-land locations of the animals through use of Doppler shifts of the frequency of received transmissions. Ultimately, diving and temperature can be reconciled with at-sea locations to compare foraging areas with locations of known prey stocks.  相似文献   

18.
The distribution and abundance of the euphausiids Thysanoessa raschi and Thysanoessa inermis in the shelf waters of the southeastern Bering Sea were investigated during spring and summer of 1980 and 1981. Experiments were conducted during the study to describe the reproduction, growth and development of these species. T. inermis was the dominant euphausiid species observed over the outer shelf region; it began spawning in early April while T. raschi dominated the euphausiids over the middle shelf and began spawning in mid or late May. The seasonal progression in spawning followed the seasonal development of temperature; however, spawning did not begin earlier in 1981 which was a warmer year than 1980. Average egg production of T . raschi ranged from 3.4% to 3.8% dry body weight of the female per day during the first three days after capture. Secondary production estimates for T . raschi females ranged from 4.2% to 5.2% dry body weight per day in 1980 and 5.9% to 6.0% dry body weight per day in 1981. A sharp decline in the abundance of adolescent and adult euphausiids over the middle shelf during the spring bloom period when food appeared to be abundant suggests that predation by diving birds, pollack. Tanner crabs, whales and seals effectively controls the euphausiid population.  相似文献   

19.
Surface crusts and seals can form from a variety of processes, both physical and biological, and have the potential to alter runoff and erosion, especially in regions with low vegetation covers. Despite the obvious links between seals and crusts these features have rarely been considered together. This study uses rainfall simulation experiments to investigate interrill soil crust and seal development in response to structural (or raindrop-impact-induced) and depositional (or runoff-induced) processes on a semiarid piedmont in southern New Mexico, USA, which has undergone substantive vegetation change (replacement of grasses by shrubs) over the last 100 years. The study design incorporates six double-paired runoff plots divided into four subplots, each of which was exposed to three rainfall simulation events. Crust development on these plots was assessed using penetration-resistance measurements while seal development was assessed using runoff coefficients. The penetration-resistance data indicate that subplots directly exposed to raindrop impacts (uncovered plots) have crusts that are  40% stronger than those positioned beneath a mesh cover (covered plots) that intercepts the kinetic energy of the rainfall. The crusts exposed to raindrop-impacts increased in strength following each simulation, whereas the crusts on the covered surfaces reached a plateau after two events.Runoff data indicate that seal development does not directly mirror crust formation. Runoff coefficients increased after each rainfall simulation event but were not significantly different between the covered and uncovered plots. Rather, the presence of stone lags or litter on the soil surface influenced the relation between runoff and seal development. Sediment yields from uncovered surfaces exceeded those from covered surfaces, indicating that raindrop impacts contribute to the delivery of sediment into flows. The results of this study indicate that the loss of vegetation cover on the piedmont has increased the extent of surface crust and seal development but that those crusts may be playing an important role in mitigating erosion.  相似文献   

20.
Just after World War II the size of the Northeast Arctic cod ( Gadus morhua ) stock was about 6 million tonnes, but at the beginning of the 1980s the stock had been reduced to 1 million tonnes, due mainly to the excessively high fishing-mortality. Nevertheless, the stock produced strong year classes at the 0-group stage in the relatively warm period 1983-1985. At the same time, individual growth in the cod stock was good, and in 1986 the stock size increased to over 1.5 million tonnes.
However, the cod preyed increasingly on the capelin ( Mallotus villosus ) present, and by the end of 1986 the capelin stock was seriously depleted. The cod compensated for the loss of capelin by preying more intensively on other food items, including smaller cod. Cannibalism increased by a factor of three from 1984 to 1986, and this is one important reason why the 1984 and 1985 year classes did not recruit to the fisheries as expected. Individual growth was dramatically reduced, and the average fish weight decreased by about 50% in most age groups. Because the quotas are in tonnes, more fish than expected were caught. This resulted in serious management problems and led to reductions both in stock size and quotas compared to the optimistic prognosis of the mid-1980s.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号