The effects of recently created water bodies upon the distribution, habitat uses and conservation, of Odonata in the Blackwater Valley; Surrey, Berkshire and Hampshire.

Bailey, J. S. (1999) The effects of recently created water bodies upon the distribution, habitat uses and conservation, of Odonata in the Blackwater Valley; Surrey, Berkshire and Hampshire. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

The Blackwater Valley on the Surrey/Hampshire border has over 70 flooded gravel workings. The value of these to Odonata was studied. Four sites were selected as representative for age, use and size of the Valley's ex-gravel workings. For these sites critical habitat factors were measured and the odonate assemblages monitored over a three year period. A transect method to monitor adults at still water was developed and refined to produce a minimum effort methodology of nine biweekly counts between June and September. This was shown to be effective in assessing the odonate assemblage present. A transect method to count exuviae was also devised to quantify breeding success. Restoration and after use of sites was shown to be important in determining species and numbers of odonates. A site restored for nature conservation supported the largest number of species. In contrast at a site restored for intensive angling, there was no evidence of breeding odonates three years after stocking. Fish populations were shown to be a major factor affecting the numbers of species and population sizes of odonates. Higher fish stocks reduced the number of species present, but Erythromma najas and Enallagma cyathigerum benefited from the presence of fish stocked at moderate densities. The habitat requirements of five selected species (Brachytron pratense, Cordulia aenea, Somatochlora metallica, Erythromma najas and Aeshna mixta) were looked at in detail. Parameters are given for vegetational structure, physical character, sediments and water chemistry for sites with breeding populations of these species. Recommendations for future monitoring, conservation action and information exchange to benefit Odonata in the Blackwater Valley and nationally are given.

Item Type:	Thesis (Doctoral)
Divisions :	Theses
Authors :	Name Email ORCID Bailey, J. S.
Date :	1999
Contributors :	Contribution Name Email ORCID http://www.loc.gov/loc.terms/relators/THS
Depositing User :	EPrints Services
Date Deposited :	09 Nov 2017 12:13
Last Modified :	15 Mar 2018 23:53
URI:	http://epubs.surrey.ac.uk/id/eprint/843172

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