摘要:

Abstract1This paper lists 171 freshwater macroinvertebrate taxa from Tenerife (excluding chironomids) based on this study and other published information. Canarian endemism and a Mediterranean origin are dominant features in the data set. At least 14 species are Tenerife endemics. Endemism is especially high in the Diptera, Trichoptera and Coleoptera.2Extensive investigations were carried out at 57 sites in six different habitat categories and from at least two seasons. The most species‐rich habitats were those with permanently running water, a biotope that is rare and diminishing in Tenerife.3The principal threat to freshwater environments is an increase in human exploitation of the water resources, which, if it is not moderated, will cause extinctions in the near future. Taxa that do not favour man‐made canals are especially at risk—a risk that is increased by the small number of populations. These include the Canarian endemicsWormaldia tagananana, Tinodes canariensis(Trichoptera),Dixa tetrica(Diptera) andBaetis pseudorhodani(Ephemeroptera). Thirty‐nine species were found at five or fewer sites.4Some species can survive in intermittent streams, although we found less than half of the taxa present in this habitat, indicating the extent of the diversity reductions that might be expected to follow the drying up of permanent streams.5Species living in the thin film of water in the madicolous habitats are similarly at risk. Three Canarian endemics were found exclusively in this habitat:Hydrotarsus pilosus, Limnebius punctatus(Coleoptera) andSatchelliella binunciolata(Diptera).6As a first step, protective measures are proposed for five of the most species‐rich streams. If these were to be implemented, they would make a significant contribution towards maintaining biodiversity in the fresh waters of

ISSN:1052-7613    

DOI:10.1002/aqc.3270050103

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Macroinvertebrate and DipperCinclus cinclusabundances and pH were assessed on four rivers in the south‐central highlands of Scotland in early winter 1990 to examine the general applicability of Dipper/acidity relationships established during the breeding season (Ormerodet al., 1985; Vickery, 1991).2The most acid waters had the lowest invertebrate biomasses and Dipper densities. Birds on these rivers spent significantly more of the morning foraging and less time at rest, apparently reflecting reduced prey capture rates and hence the greater time required to replace overnight mass losses.3Analysis of published data on seasonal changes in Dipper population densities and individual energetic demands suggests that even accounting for the higher numbers of Dippers in all habitats during autumn and winter, energetic requirements both of individuals and populations are greatest during breeding, when the costs of self maintenance are coupled with the additional demands of chick rearing.4However, from the patterns found here and elsewhere during autumn it appears that the effects of acidity on Dipper populations are important generally during both the breeding and non‐breeding seas

ISSN:1052-7613    

DOI:10.1002/aqc.3270050104

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Fluvial maintenance is frequently undertaken to preserve the flood capacity, visual amenity, conservation value and geomorphic stability of managed river channels. Maintenance tasks include the management of both riparian and in‐channel vegetation and maintenance dredging.2Riparian vegetation is traditionally managed by physical methods such as cutting of grasses or removal of trees. Less environmentally severe alternative practices include grazing or shading for grasses, and practices such as pollarding or coppicing for trees.3While a range of alternative maintenance practices, with varying environmental impact, are usually available for river managers to select, the potential for improving maintenance practices varies according to the particular task considered and the constraints imposed by the need to reach and maintain the target standard of service in terms of flood defence and land drainage.4This review shows that economic and environmental impacts associated with fluvial maintenance operations may be reduced at three scales. First, at the smallest scale, it is shown that there is often potential for improving the local operational efficiency of individual fluvial maintenance tasks. Second, it may be possible to reduce the intensity of maintenance in channel reaches which are presently over‐serviced. Third, at the largest scale, it is shown that efficient maintenance is best achieved within the framework of Integrated Basin Management, and by giving appropriate consideration to future maintenance requirements at the design stage of new projects to reduce the overall need for fluvial maintenance. Examples of the way in which these policies may be implemented to reduce environmental impact without compromising engineering objectives are illustrated through case studies from the UK and the

ISSN:1052-7613    

DOI:10.1002/aqc.3270050105

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Hong Kong has suffered from gross water pollution, as a direct consequence of the territory's rapid growth in population and in industrial and commercial prosperity. In 1989, the government of Hong Kong adopted a comprehensive strategy for water pollution control. Water quality monitoring is essential to the success of this strategy.2The monitoring programme was designed rationally to provide the information required to detect progress towards (or away from) water quality objectives. Practical constraints have prevented the ideal implementation but the programme gives comprehensive coverage of marine waters, including bathing beaches and inland waters.3Sampling and analytical methods are an important part of programme design, to ensure that the programme yields accurate and consistent data. Presentation and interpretation also need to be taken into account. More effort on interpretation of a well‐designed survey can reduce the effort required for sampling and analysis.4Examples show how the monitoring programme has been used for practical environmental management purposes, including the control of dredging operations, the justification of new sewage disposal facilities, and the control of waste from the livestock industr

ISSN:1052-7613    

DOI:10.1002/aqc.3270050106

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Despite the ease with which shark stocks can be quickly overfished, illustrated by the collapse of similar fisheries in the past, few regulations currently exist for the effective management of present day fisheries.2Large numbers of sharks are taken by both commercial and recreational fisheries around the British Isles; current landings are reviewed.3These data are used to support the contention that immediate research is undertaken to collect essential life‐history information so that (i) accurate assessments of current stock levels can be made and (ii) a long‐term fishery management plan can be develo

ISSN:1052-7613    

DOI:10.1002/aqc.3270050107

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050108

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050109

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050111

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050112

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050102

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY