摘要:

Abstract1. The impact of land‐claim on the intertidal areas of the Forth estuary, eastern Scotland is described. It is shown that in recent times almost 50% of the intertidal area has been destroyed for a variety of purposes, including agriculture, harbours and industrial development.2. The loss of infaunal invertebrate biomass and production from the intertidal habitat has been calculated for each part of the estuary, and by summation for the whole estuary. The loss is discussed in relation to the total biomass and production, both intertidally and subtidally, of the estuary. It is shown that proportionately more biomass and production may have been lost than area.3. The impact of land‐claim on estuarine fish is calculated. Land‐claim has removed 24% of the natural fish habitats in the Forth estuary, and thereby removed 40% of their food supply.4. The impact of habitat loss on birds was observed for one area where observations continued throughout a period of land‐claim. For individual bird species at Torry Bay, land‐claim had consequences ranging from neutral to substantially negative. Significant declines were found for overwintering populations of dunlin and bar‐tailed godwit. Comparisons of pre‐ and post‐land‐claim bird feeding usage of this area, showed that the impact of land‐claim on local bird populations differed between species. The large scale loss of habitat on the Forth seems likely to have reduced the size of some shorebird populations which overwinter on the estuary.5. It is concluded that when considering the impact of land‐claim on estuaries that, as found in some previous studies, a simple consideration of area lost may be inadequate to describe the effects of land‐claim, and the consequences for animals living within the estuary may differ considerably amongst themselve

ISSN:1052-7613    

DOI:10.1002/aqc.3270020302

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract1. A survey was carried out in rivers, canals and large lakes in the province of Overijssel (The Netherlands) to describe the macrofauna assemblages and their environment. A total of 74 environmental variables was measured at each sampling site. The aim was to describe a typology of large‐sized water bodies for this region.2. Different techniques of multivariate analysis were used in combination with ecological information on individual taxa to derive and describe site groups in terms of taxon composition and mean environmental conditions. The resulting site groups were termed cenotypes.3. Nine cenotypes were distinguished. They showed great similarity in their composition of ubiquitous taxa and in environmental conditions. This similarity is, in part, due to anthropogenic influences. The large‐sized water bodies are mostly regulated or canalized and function as collectors of nutrients, organic material and toxicants. This results in cumulative chronic stresses which overrule the natural key factors of current and dimension.4. Despite the similarity, differences between taxon assemblages could be attributed to combinations of key environmental factors; some taxa characteristic of the reach of a river or the gradient in size of canals were still present.5. The typology offers a basis for practical use in regional water management and nature conservation. Some applications for water management are indicated.6. Typological studies are vital (especially in semi‐natural landscapes) for an improvement in understanding, management and conservation of freshwater

ISSN:1052-7613    

DOI:10.1002/aqc.3270020303

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract1.Perca fluviatiliswas sampled monthly over 2 years from the shallow waters (120 mm long) in spring, summer and autumn.3. All size groups ofP. fluviatilisfed on the small indigenous teleostsEdelia vittataandBostockia porosa.4. The prevalence with which the different size groups ofP. fluviatilisingested indigenous fish species in the main channel of the river was as high as 14% in fish120 mm long in autumn.5. Despite appreciable predation and a relatively high prevalence ofP. fluviatilis, indigenous fish species have coexisted with perch in the Collie River since the early 1900s. Such coexistence has apparently been facilitated by a high density of invertebrate prey (as a result of eutrophication) and limited interspecific dietary overlap.6. The absence ofE. vittatain those parts of a nearby river system now occupied byP. fluviatilisand the extremely high prevalence of fish that is sometimes found inP. fluviatilisstomachs, suggest that under certain extreme conditions, such as when a marked depletion in alternative food sources occurs, the presence of perch could pose a threat to the conservation of indigenous fish species in certain river systems in south‐western Aust

ISSN:1052-7613    

DOI:10.1002/aqc.3270020304

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract1. The most important area in Singapore for native aquatic fauna and flora is a relatively intact 5 km2patch of freshwater swamp forest in Nee Soon.2. The Nee Soon Swamp Forest contains 48% of the primary freshwater fish, 71% of the amphibian, 28% of the reptile and 34% of the bird fauna of Singapore. The swamp also has the highest percentage of native and threatened freshwater fish and crustacean species on the island, as well as being the main (if not the only) habitat of the aquatic plantHydrostemma. It is also the last refuge of two mammals, the Banded Leaf Monkey,Presbytis femoralis femoralis, and the Cream‐coloured Giant Squirrel,Ratufa affinis affinis.3. The threats to the swamp forest are discussed, and proposals are made to establish the swamp forest as Singapore's second major nature reserve.4. Study of the swamp forest is essentially still at a survey and discovery phase. The research priorities are to establish detailed species lists, the status of endangered species and the extent of buffer zones.5. The swamp forest is administered primarily by the newly established National Parks Board, but several other government organizations also have jurisdiction over the land, causing some problems in the management of the swamp. The roles of the university and non‐governmental organizations in conducting surveys, drafting recommendations and educating the general public are detai

ISSN:1052-7613    

DOI:10.1002/aqc.3270020305

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract1. Sample areas of the county were used to estimate pond loss. An extensive survey used only maps while a smaller, intensive survey combined maps with a field study. In total, 283.43 km2were surveyed, approximately 7% of the total area.2. Fifty‐five per cent of the ponds present in 1870 had disappeared by 1960 with the greatest loss occurring between 1920 and 1960.3. Loss of ponds in agricultural locations contributed most to this because of their high initial number and their high rates of loss. Percentage losses of large and small ponds were greater than for medium‐sized ponds.4. A field survey showed that a further 23% of a random sample of ponds shown on maps of 1960 could not be found in 1989. Overall loss rates for the period 1870–1989 are estimated to be 68.6% for the extensive area and 54.8% for the intensive

ISSN:1052-7613    

DOI:10.1002/aqc.3270020306

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract1. New land has been ‘won’ from the sea by the process of embankment for centuries. It is perhaps not surprising, given the long term commitment to the protection of the land so created, that current works are concerned largely with reinforcing the existing line of sea defence.2. Those concerned with nature conservation have likewise in the past, expended considerable energy in trying to protect natural and semi‐natural habitat from destruction and exploitation by man. This has included land claim and associated sea defence works.3. This paper examines these two perceptions of ‘coastal protection’ and suggests a more enlightened approach which accepts change as an important part of coastal development, and provides a more positive way forward. Those concerned with sea defence and nature conservation may have to accept that protection of the current line of sea defence or existing coastal habitats, may not be the best option in

ISSN:1052-7613    

DOI:10.1002/aqc.3270020307

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270020308

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270020309

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270020310

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270020311

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY