摘要:

Abstract1Hatchery‐reared Pacific oysters (Crassostrea gigas) grown in the British Isles and Guernsey originate from an introduction through quarantine of small numbers of oysters from British Columbia, Canada.2Previous electrophoretic analysis of samples of these oysters have shown the glucose phosphate isomerase locus to be monomorphic.3Recent analysis of oysters from a commercial hatchery in Guernsey revealed a second allele at low frequencies which was unexpected and was thought to indicate the presence of oysters from another stock.4Samples of hatchery‐reared oysters from France showed that they were highly polymorphic and carried the unexpected allele and four others.5A natural spatfall of oysters from the River Teign (Devon) was sampled and these carried three alleles which were also found in the FrenchC. gigas.This suggests that there has been movement ofC. gigaspossibly of French origin into this river.6This finding and its implications in terms of conservation and management are discus

ISSN:1052-7613    

DOI:10.1002/aqc.3270050302

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Lord Howe Island, a World Heritage Area which lies in the southern Pacific Ocean, has the most southern true coral reefs in the world.2In the past decade, populations ofAcanthaster planci, the crown‐of‐thorns starfish, have significantly reduced coral cover at Elizabeth and Middleton Reefs, approximately 200 km to the north of Lord Howe Island, and a small population has been reported from Lord Howe Island.3The abundance and distribution ofA. planciwas evaluated using surveys by the local recreational diving industry and video‐transects, and the potential rate of recovery of the coral community following predation was assessed by analysing coral recruitment patterns.4The starfish population at Lord Howe Island remained relatively small and localized between 1984 and 1993.5Coral recruitment was dominated by the juveniles of brooding corals, and these same species dominated the established coral community. There was limited recruitment of broadcast‐spawning coral species during the study period, suggesting that southern dispersal of coral larvae from more northern sites may be a rare or sporadic event.6The results indicate that there is only a small probability that the present starfish population will result in a major starfish outbreak. However, the recovery of the coral community from a major outbreak would be slow because of the apparently low rate of input of coral larvae from sources external to the reef.7Management agencies need to consider whether the present small and localized starfish population should be removed, given the likely ramifications of an infestation and the economic importance of the reef to

ISSN:1052-7613    

DOI:10.1002/aqc.3270050303

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Records for 102 Sites of Special Scientific Interest (SSSIs) in England were examined for eutrophic status and for symptoms of eutrophication using criteria established by the Department of the Environment (DoE). Seventy‐eight were found to be eutrophic or hyper‐eutrophic using total phosphorus criteria. Of the 102 sites, 85 cases (84%) showed symptoms of eutrophication. This had changed overtly the nature conservation interest in 69 cases.2The 102 sites were contracted to 96 by listing together eight adjacent SSSIs in the Somerset Levels and treating another split‐site SSSI with separate catchments within it as two sites. Within these 96, 17 did not show symptoms of eutrophication and 79 (84%) did. Of the 79 cases, a major cause of the eutrophication in 35 (44%) was sewage effluent with a further five possible cases of effluent problems. The second most important cause (15 sites (19%) and potentially a further six, of the 79 sites) was attributed to the effects of common carp (Cyprinus carpio), and to a lesser extent common bream (Abramis brama), in mobilizing nutrients and increasing turbidity within the water body.3Symptoms of deterioration were most frequently recorded in the aquatic plant communities, probably because these are most readily observed. Comparable changes should be expected in animal communities but these are infrequently monitored. There may have been unrecorded changes in some sites that had nonetheless suffered damage. It is likely that detailed studies of sites where there is clear evidence of eutrophication will reveal some deterioration in conservation interest.4The primary management required to help restore the conservation interest in the 79 sites involves phosphorus removal from, or diversion of, sewage effluent in at least 30 cases. Of these two‐thirds (20) will fall outside the current arrangements being made by the DoE for the application of the Urban Waste Water Treatment Directive. Removal of carp and additional biomanipulative measures are suggested for at least 18 cases (23%) and fishery modifications in a further six, giving a total of 30% of sites where fish are a part of the problem. Further investigation is needed in nearly half of all cases where the situation is not entirely clear.5The data available from statutory bodies to assess the trophic states of the sites examined were generally inadequate. Total phosphorus, a key variable in the currently recommended DoE scheme, and widely recognized as very important by the limnological community, is not routinely monitored by the National Rivers Authority (NRA), and methods used for soluble reactive phosphorus are not generally used with a sufficiently low detectio

ISSN:1052-7613    

DOI:10.1002/aqc.3270050304

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Some effects of fisheries on the associated biological systems are reviewed and management options and their inherent risks are considered.2In addition to the effects on target species, other sensitive groups impacted by fishing are considered including marine mammals, turtles, sea birds, elasmobranchs and some invertebrates with low reproductive rates.3Other impacts discussed include the destruction of benthic habitat, the provision of unnatural sources of food and the generation of debris.4Management options are considered including the designation of marine protected areas, risk aversion, and the burden of proof.5A balanced consideration of the risks and consequences of ‚Type 1’︁ and ‚Type II’︁ errors i

ISSN:1052-7613    

DOI:10.1002/aqc.3270050305

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract1Climatic changes and water resource developments alter the relative contribution of the water sources (glacier‐melt, snow‐melt, rainfall run‐off and springflow) to the discharge regime of alpine streams.2Likely changes in the magnitude and variability of a range of climatic determinants of glacier behaviour, as a result of an enhanced Greenhouse Effect, are shown to have important implications for the future hydrogeomorphological and thermal dynamics of alpine streams.3Zoobenthic communities typically show deterministic patterns in alpine streams due to the over‐riding influence of water temperature and channel stability. These communities could act as indicators of change in the relative contribution of run‐off, particularly to alterations of glacier‐melt patterns.4A reduction of glacial meltwater, following diversion for HEP generation, is used as an example to illustrate the sensitivity of the zoobenthic communities to changes in temperature and flow regimes, and geomorphologic

ISSN:1052-7613    

DOI:10.1002/aqc.3270050306

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050307

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050309

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050310

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050311

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270050312

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY