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61.
Colin E. Nash 《Aquaculture (Amsterdam, Netherlands)》2004,240(1-4):623-625
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- 1 Fluvial 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.
- 2 Riparian 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.
- 3 While 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.
- 4 This 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 USA.
64.
Allelic losses and gains during translocations of a high conservation value fish,Coregonus lavaretus
Kim Præbel Colin W. Bean Jennifer A. Dodd Elizabeth C. Etheridge Andrew R.D. Gowans Rune Knudsen Alexander A. Lyle Peter S. Maitland Ian J. Winfield Colin E. Adams 《水产资源保护:海洋与淡水生态系统》2021,31(9):2575-2585
- The use of translocations to establish new or ‘refuge’ populations for species with high conservation value is controversial but widely used in conservation management. One of the risks of this approach is that an establishing population does not adequately capture the genetic diversity of the donor gene pool. This effect, rarely examined, is tested here.
- In this study the genetic consequences of two conservation translocations after five generations (16 years) of the European whitefish, Coregonus lavaretus, were quantified. Both translocations were made using almost the same genetic groups and thus represent a partly replicated natural study.
- Analysis of 12 informative microsatellites showed that expected heterozygosity, the mean number of alleles per locus and allelic richness did not differ between donor and translocated populations. There was also no loss of heterozygosity in the translocated populations, nor deviations from Hardy–Weinberg equilibrium expectations, nor signs of linkage disequilibrium.
- All populations were genetically differentiated but pairwise FST values were low, indicating that the magnitude of divergence was small.
- There was no evidence of inbreeding but there were significant differences in private allelic richness between donor and translocated populations. Of 50 alleles found in the donor population, 16% of the rarer alleles were lost in one translocated population and 8% in the other.
- Allele loss without a reduction in heterozygosity strongly points to stochastic drift effects having occurred following translocation. The evidence indicates that alleles that were not detected in the donor population have arisen de novo in the translocated populations.
- It is concluded that conservation translocations comprising even a modest number of propagules can successfully capture a high proportion of genetic variation of the host population, and that reduced genetic variation in the translocated population may be mitigated by the emergence of new variation over short time periods.
65.
This paper is the sequel to an earlier publication (see Biological Conservation, Vol. 5, No. 4 pp. 243–250, October 1973) on the conservation status of deer and describes an IUCN programme for the conservation of world-threatened deer. Research requirements for conservation of deer that are currently threatened with extinction are discussed. The immediate conservation objective is to ensure the species' or subspecies' survival, and the long-term objective is to restore their productive status in the wild. A framework for research to provide data to guide conservation practices is outlined. It comprises a set of research questions, to aid the planning of studies, and statements of the conservation action potential of the results of these investigations. The proposed organization of the IUCN programme and its current status is described. University and other research institutions that would be interested in participating or co-operating in the programme are invited to write to IUCN. 相似文献
66.
Equine Post-anesthetic Lameness A Retrospective Study 总被引:1,自引:0,他引:1
MEGHAN T. RICHEY DVM MELISSA S. HOLLAND DVM DiplomateACVA CHARLES J. McGRATH DVM DiplomateACVA NICHOLAS H. DODMAN BVMS MRCVS DVA DipomateACVA DURWOOD B. MARSHALL ESS MICHAEL H. COURT BVSc DiplomateACVA WENDY M. NORMAN BVSc DAVID C. SEELER DVM MSC DiplomateACVA 《Veterinary surgery : VS》1990,19(5):392-397
The incidence of post-anesthetic lameness in 655 horses undergoing 733 anesthetic episodes over a 3 year period was 6.4%. Nineteen factors previously reported or proposed to play a role in the development of post-anesthetic lameness were evaluated statistically. Only hypotension and the duration of the anesthetic period were significant factors. 相似文献
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69.
Despite the phenomenon of heterosis having been used to improve crop productivity for almost a century, there is little understanding
of the molecular mechanisms involved. Heterosis has been described recently in the widely used plant model Arabidopsis thaliana. To assess the opportunity afforded by this system, we have developed, through pollination to a male sterile female parent
(Ler ms1), a range of hybrids of A. thaliana accessions. We tested this method of hybrid production in A. thaliana by comparing seed produced by natural pollination and hand pollination of emasculated plants. Our results demonstrate that
using male sterile lines, which more closely represent methods used for hybrid crop production, circumvents the problems associated
with the analysis of hybrids produced from emasculated plants. We identified hybrid combinations exhibiting mid-parent heterosis
for vegetative fresh weight ranging from −9 to 103% and characterised heterosis in the reciprocal hybrids of one strongly
heterotic combination. We found no evidence of a relationship between the extent of genetic relatedness of A. thaliana accessions and the strength of heterosis exhibited by their hybrids.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
70.
Summary Cannabis sativa, is a rich source of a variety of compounds, including cannabinoids, terpenoids and flavonoids. Their content depends upon the plant genetics, growth conditions, time of harvest and drying conditions. To date, more than 60 different cannabinoids have been identified in the plant. Cannabis has been used medicinally for 4000 years and remained in the British pharmacopaeia until 1932, and in the British Pharmaceutical Codex until 1949. Medical use has been prohibited in the UK since 1973. The principal cannabinoid, delta-9-tetrahydrocannabinol (THC) was first isolated in 1964; the first cannabinoid pharmaceutical product Marinol® (a synthetic THC product) was approved in the USA in 1985. The discovery of specific cannabinoid receptors in the early 1990s and subsequent identification of the endocannabinoids anandamide and 2-arachadonoylglycerol, led to a resurgence of interest in the field of cannabinoid medicine, especially within the pharmaceutical industry. Cannabidiol (CBD), as a non-psychoactive, cannabinoid is currently a cannabinoid of significant interest, showing a wide range of pharmacological activity. The other classes of compounds present in cannabis also have their own pharmacology (e.g. terpenoids, flavonoids). The potential for interaction and synergy between compounds within the plant, may play a role in the therapeutic potential of cannabis. This may explain why a cannabis-based medicine using extracts containing multiple cannabinoids, in defined ratios, and other non-cannabinoid fractions, may provide better therapeutic success and be better tolerated than the single synthetic cannabinoid medicines currently available. The development and employment of one of these medicines, Sativex®, is described. 相似文献