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 562 毫秒
1.
In this paper, numerical modelling of the fluctuation of the thermocline in the Bohai Sea has been made using a two-dimensional nonlinear model in stratified ocean and the model for the depth of the thermocline under the effects of wind stirring. The computed results depict the variations of the fluctuation of the thermocline driven by different kinds of wind fields. The fluctuation of the thermocline in the Bohai Sea varies somewhat with different directions, paths and locations of typhoon (cyclone). Under the effects of strong wind, the thermoclines both sink due to mixing and fluctuate. Furthermore, the fluctuation of the thermocline speeds up mixing. At last, the thermoclines disappear after 12-15 h when the strong wind increases from Force 6 to Force 9.  相似文献   

2.
Fish communities over continental shelves are of three types: pelagic, rocky reef and soft substrata. The pelagic community of the South African west coast is dominated by clupeiform fish, which are the principal prey of snoek, the dominant piscivorous teleost in the area, and other fish, including tuna and pelagic sharks. Keystone prey species are broadly similar on the South African south and west coasts, but predator composition differs. Studies of rocky reef fish suggest that the fauna of the South Coast is more diverse than that of the West, the West Coast having fewer species and only two reef fish species being taken in linefisheries. Feeding interactions of some of the dominant species have been established, but the status of commercially less important fish such as elasmobranchs and small species is poorly known. The community and feeding interactions of fish living over soft substrata are better known and part of this fauna is taken by demersal trawlers. The two species of Cape hake dominate the communities on both coasts, but the fauna is more diverse on the Cape south coast. Generally, much of the present ichthyological knowledge is derived from the ecologically narrow perspective of commercial fisheries. Nevertheless, the patterns of diversity appear to conform to previous work, which has indicated a lower species diversity in the Atlantic than in the Indian Ocean. Knowledge of commercially unimportant fish is fragmentary, and understanding of the ecological interactions on the South Coast generally lags that of the West.  相似文献   

3.
Study on abundance variation of pteropods in the East China Sea   总被引：5，自引：0，他引：5  
1 Introduction Pteropoda, an order of marine pelagic mollusks, belongstoClassGastropoda,SubclassOpisthobranchia. The speciesofthisorder can be found all over the world buttheyareusuallyabundantinthecontinentalshelfand continental slope area. As fish diets…  相似文献   

4.
The distribution of dissolved oxygen in the western Taiwan Strait was discussed by using the method of harmonic analysis. The periodic variation of dissolved oxygen in seawatcr can be expressed by the Fourier series:whereto is annual average value; Am andφm are amplitude and phase of constituent, respectively. The distribution of A0 and the annual and semiannual constants (Am, φm) of dissolved oxygen in the surface, bottom and vertical section of the western Taiwan Strait were described. The effect of the various currents on the distribution of dissolved oxygen was also discussed.  相似文献   

5.
We make an attempt to study specific features of weather- and climate-forming processes developing due to the energy and mass transfer between the ocean and the atmosphere in the North Atlantic, as well as responses of the climate of Ukraine to the main climate-forming factors. These studies are based on a statistical model in the form of a system of third-order regression equations with feedback. We deduce a system of generating functions that allow us to estimate the regression coefficients. Within the developed model, we applied the factor analysis to compress the input information about the affecting factors in the region where the weather ships were located. This allowed us to reveal the tendencies of variations in the characteristics participating in the energy and mass transfer. The response of the climate in various regions of Ukraine to the processes running in the North Atlantic was determined using the cluster analysis whose algorithm was developed by the authors. We performed a number of experiments for various situations in the region of the North Atlantic that are possible due to the global warming of the climate and studied the response of climatic characteristics on the territory of Ukraine under similar processes. The adequacy of the developed model was verified on the basis of data on the real situation in February 2006. It is shown that the model satisfactorily describes the responses of climatic characteristics in regions of Ukraine to variations of the affecting factors in the North Atlantic.  相似文献   

6.
The biomasses of fishes at the bottom layer of the Bohai Sea are extimated by analysing the data on samples (447 hauls,more than 0.2 million in number or 20 t in weight of fishes) collected monthly by our institute from April, 1982 to May, 1983 by a pair of bottom trawls through the Bohai Sea. The exploitation problems are also discussed in this paper.  相似文献   

7.
ThisstudywassupportedbytheStateEducationalCommittee(SEC)ofChina.INTRODUCTIONThedissolvedorganiccarbon(DOC),ordissolvedorganicmatter(DOM),isoneofthemostimPortantorganiccarbonreservoiroftheworld,whichmayaffectthecontentofCO2intheatmospherewithatime-scaleof1OOO~1OOOOyears(Hedges,1992).Theratesofproduction,degradationortransPortationofDOCareseveralmaindynamicalparametersofDOCintheeu-photiclayer.Inthispaper,wefocusonthediurnalvariationsofDOCinordertoestimatetheseparameters.METso…  相似文献   

8.
This paper discusses the long-term variation in the salinity of the Southern Yellow Sea Cold Water Mass (SYSCWM) and examines factors influencing the SYSCWM based on hydrographic datasets of the China National Standard section and the Korea Oceanographic Data Center. The mean salinity at the center of the SYSCWM showed a decreasing long-term trend. In empirical orthogonal function (EOF) analysis, the second EOF mode showed a similar long-term trend. The mean salinity of the center of the SYSCWM was related to the intrusion of saline water from the Yellow Sea Warm Current (YSWC), the salinity of the source area of the YSWC, the evaporation minus precipitation (E–P) flux, and discharge from the Changjiang River. The decreasing salinity trend to the southwest of Cheju Island produced a freshening trend in the YSWC, resulting in a reduction in the salinity of the SYSCWM. The freshening trends of the water from the northwest Pacific and the South China Sea were seen as the reason for the decreasing salinity trend from the intrusion of water into the Yellow Sea (YS). The freshwater flux influenced the surface salinity and was brought to deep layers by strong mixing in winter. The mean E–P flux signal and Changjiang River discharge signal lagged the first principal component of the SYSCWM by approximately 5 months.  相似文献   

9.
On the basis of the observation data of Kuroshio since 1984 and relative historical data in the East China Sea, spatial and temporal variation of water mass mixing characteristic in the observation area is analysed. The main results are as follows.  相似文献   

10.
Gravel occurred in. the stomachs of 17.8% of 924 Galaxias vulgaris and 2.8% of 430 Philypnodon breviceps taken from the Glentui River, Canterbury, between June 1970 and November 1971. It is suggested that differences in feeding habits and feeding locality are responsible for the difference in occurrence of gravel in the stomachs of the two fish species. Galaxias vulgaris feeds in the water column in riffles and, being a drift feeder, is more likely to ingest inedible material by accident than is P. breviceps, which feeds on the bottom in sheltered or quiet stretches of the river.  相似文献   

11.
On the basis of the analysis of the data obtained from five cruises of the R/V Xiangyanghong 09 and the data from Japan, it is shown that a large meander of the Kuroshio appeared again during 1986-1988. The processes of formation , maturity and decline of this large meander are discussed in this study. The variation of the volume transport at Section Kb (PN) in the East China Sea is related to the large meander of the Kuroshio in the area south of Japan. By using maximum entropy spectrum analysis,the volume transport of the Kuroshio and the swing of its axis are analysed and their major periods are obained.  相似文献   

12.
《Ocean & Coastal Management》2003,46(9-10):917-941
What influence do exchange methods have on ex-vessel prices and what are the potential implications for the regional management of the fisheries? This paper undertakes an empirical analysis of exchange methods and ex-vessel prices for specific demersal fish controlled for fish size and quantity in four North Atlantic regions, including Iceland, North-Norway and Scotland. The methodology consists of a comparative analysis of total average price (TAP) and Anova analysis of monthly average prices of cod and plaice landed fresh during the period 1990–1999. Scotland's auctions have the highest TAPs for the species analysed whilst the lowest TAPs are returned from contract sales in Iceland and North-Norway. Icelandic auctions and Møre–Romsdal auctions adopt intermediate positions in this price hierarchy. Price differences are still present even when correcting for factors such as legal barriers, transport costs from different geographical locations, exchange fees and seasonal variations in supplies. The implications of these findings for current and prospective systems of regional resource and coastal management are then considered and the scope and need for further study is established.  相似文献   

13.
Ecosystem changes currently question the traditional allocation of fishing rights and quotas in the fishery of Northeast Atlantic mackerel and Norwegian spring-spawning herring in the Northeast Atlantic. Variability in the distribution of these highly migratory species escalated in a political conflict between member states of the European Union, Iceland, the Faroe Islands and Norway, which is a driving force for unsustainable fishery. The aim of this paper is to investigate this conflict by outlining the social understandings of diverse stakeholders by using the Q methodology. The method reduced the complexity of numerous opinions, detected four distinct perspectives and simultaneously categorised the participating stakeholders. Although the perspectives differ in various elements, the protection of economic interests seems to dominate over the quest for sustainability. The call of all stakeholders in this study to clarify the fishing rights in the Northeast Atlantic reveals a clear deficiency of the current international fishery management in handling abrupt ecological changes and the necessity to acknowledge this as a complex adaptive system.  相似文献   

14.
1Introduction Besidestheprecipitationandriverdischarges,the watersinthePacificOceanandtheAtlanticOceanare thesourcesoftheArcticOceanwater.TheAtlantic waterenterstheArcticOceanviatheFramStraitand theBarentsSea.Foritsdenserfeatureduetohigh salinity,mostofitsinkstothenorthofSvaldbardand circulatesinallthedeepbasinsintheArcticOcean, formingthedeepandbottomwatersoftheArcticO- cean(Aagaardetal.,1985;Rudelsetal.,1999).The BeringStraitistheonlychannelforthePacificwater toflowintotheArcticOce…  相似文献   

15.
It is generally accepted that a climate shift occurred about 1977 that affected the dynamics of North Pacific marine ecosystems. Agreement on the possibility of further climate shifts in 1989 and the late 1990s is yet to be achieved. However, there have been changes in the dynamics of key commercial fishes that indicate changes in their environment occurred in the early 1990s, and possibly around 1998. One method of measuring climate change is to observe the dynamics of species that could be affected.Several studies have described decadal-scale changes in North Pacific climate–ocean conditions. Generally, these studies focus on a single index. Using principal components analysis, we use a composite index based on three aspects of climate ocean conditions: the Aleutian Low Pressure Index, the Pacific Atmospheric Circulation Index and the Pacific Interdecadal Oscillation Index. We link this composite index (Atmospheric Forcing Index) to decadal-scale changes in British Columbia salmon and other fish populations. Around 1989 there was a change from intense Aleutian Lows (above average south-westerly and westerly circulation patterns and warming of coastal sea surface temperatures) to average Aleutian Lows (less frequent south-westerly and westerly circulation and slightly cooler coastal sea surface temperatures in winter). These climate–ocean changes were associated with changes in the abundance and ocean survival of salmon (Oncorhynchus spp.), distribution and spawning behaviour of hake (Merluccius productus) and sardines (Sardinops sagax) and in recruitment patterns of several groundfish species.  相似文献   

16.
Acanthogobius ommaturus, which belongs to the family Gobiidae, is a euryhaline and demersal fish that is widely distributed in the coastal areas, harbors, and estuaries of China, D. P. R. Korea and Japan. In this study, the genetic diversity and genetic structure of five geographical populations of A. ommaturus was assessed using the mitochondrial hypervariable region gene and microsatellite markers. The results of the two genetic markers indicated that the A. ommaturus populations had a high le...  相似文献   

17.
On the basis of perennial monthly mean temperature and salinity data, the classification of monthly water masses at the surface and the bottom in the Bohai Sea, the Huanghai Sea and the East China Sea, has been made by using the method of fuzzy cluster from the modified characteristic of water masses in the shallow water area. In this paper, the basic features, growth and decline patterns of water masses in relation to fishing grounds in the whole shelves of the Bohai Sea, the Huanghai Sea and the East China Sea are discussed with emphasis.  相似文献   

18.
The reasons why most small-rights holders do not participate in management of the fishery for small pelagic fish (‘small pelagics’) in South Africa, despite legislation and policy encouraging their participation, were analysed. Membership of the Small Pelagics Management Working Group (SPMWG), the main participatory governance organ, is limited to representatives of recognised stakeholder associations. Rights holders therefore have to belong to a stakeholder association, which then selects a member or members to represent them on the SPMWG. Small quotas and the difficulties of sourcing capital mean that small-rights holders are not able to invest in infrastructure. Besides, most of the small-rights holders and their companies lack experience and management skills to survive independently in this highly competitive industry, which is based on high volume and low profit margins. As a result, most of the small-rights holders have no option but to enter into complex catching and processing agreements with vessel- and factory owners belonging to the existing recognised stakeholder associations. For the small-rights holders, it does not make sense to join these associations or even to form their own if they cannot actively participate in the industry independently. Greater participation by small-rights holders should start with their genuine integration into the industry through improved ability to invest in infrastructure and through management skills development. Most likely, this will require an interventionist approach by government.  相似文献   

19.
Abundances of the fireworm Hermodice carunculata were counted through a monitoring assessment study of fish cages in Barranco Hondo（NE Tenerife）. Seven campaigns were conducted from November 2007 to June 2010 and temporal variations were found, as well as differences among sampling stations. The polychaete H. carunculata obtained its highest abundance in sediments beneath fish cages throughout the study period. Thus, the assemblages of this omnivorous species were favoured by the presence of fish cages.  相似文献   

20.
-On the basis of the data obtained from the surveys in the Bohai Sea during 1982-1983, this paper analysed and discussed the distribution and seasonal variation of primary productivity in the Bohai Sea, and the correlations between the primary productivity and environmental factors. The organic carbon production and prospect of fishery production in the waters of this sea are estimated. It is shown that, there exists production patential in the Bohai Sea, the primary production is 112 gC/ (m2 ?a)the production of organic carbon being 10 million ton per year, the fishery yields 1 million ton and the maximum catch of sea products 0. 5 million ton. The results of the investigation can serve as the basic data for the exploitation, utilization and management of the fishery resources in the Bohai Sea.  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