Assessment of the Condition of the White-Clawed Crayfish Austropotamobius pallipes in the River Wye Special Area of Conservation in 2014-2016
Between October 2014 and September 2016 work was undertaken to provide the data required to assess whether the River Wye Special Area of Conservation (SAC) was in favourable condition for the white-clawed crayfish Austropotamobius pallipes. The Afon Edw, Nant yr Offeiriad, Sgithwen Brook, Dulas Brook (Builth Road), Clyro Brook and Afon Llynfi were surveyed to assess the condition of both crayfish populations and crayfish habitat. A further two rivers (Afon Duhonw and Afon Irfon) make up the full complement of the Wye SAC tributaries but no crayfish were found in these two rivers in 2003 and there are no subsequent records, so these were not surveyed during the current survey and it is assumed that no white-clawed crayfish are present in these two rivers for this assessment. Sampling followed the methodology developed during the 2003 monitoring programme (Rogers & Watson 2004) and included a combination of manual searching and trapping. During the survey, white-clawed crayfish were only found in three of the eight tributaries of the River Wye SAC: Nant yr Offeiriad, Sgithwen Brook and Clyro Brook (although the latter is not included as part of the SAC, it is included within the condition assessment). Whilst crayfish numbers were relatively robust in Nant yr Offeiriad and Sgithwen Brook, populations have now become confined to the headwaters. In 2016, Clyro Brook still supports a thriving population as it did in 2003, and this now appears to be one of the most important populations in the Wye because there is no diminution in numbers or extent as in the Sgithwen and Offeiriad. In fact, both numbers and extent have increased in the Clyro. The lack of white-clawed crayfish in the Afon Edw, following a mortality in 2006, is worrying given that this has been a very important waterway for this species in the recent past. Also, there appeared to be no crayfish left in Dulas Brook (Builth Road) in 2015 despite supporting a good population in downstream reaches in 2003. Using the provisional conservation objectives as part of the assessment of Favourable Conservation Status for Natura 2000 features, the 2014 - 2016 survey shows the River Wye SAC does not achieve Favourable Conservation Status. Despite abundant suitable habitat (Attribute 3) and a lack of disease and the absence of aliens (Attribute 4), the density of crayfish throughout is not high enough (Attribute 1) and the distribution throughout the monitoring units is not sufficient (Attribute 2) for the River Wye SAC to achieve Favourable Status. In 2013-14, the Natural Resources Wales' Cynrig Fish Culture Unit implanted approximately 3000 crayfish into Afon Chwefru, a tributary of the Irfon. As part of the present work, an additional survey of a 1km stretch in two 500 metre sections at the introduction sites was included but no crayfish were found. Recommendations include a review of protection for surviving white-clawed crayfish populations and further survey work to verify the presence/absence of native and alien crayfish throughout the main River Wye and all tributaries and sub-tributaries. Given the importance of Clyro Brook for crayfish, it is recommended that this tributary is notified as part of the Wye Site of Special Scientific Interest and Wye SAC. [This report provides an amalgamation of the 2014, 2015 and 2016 crayfish survey results, and supersedes the 2014 and 2015 survey reports (Rogers & Watson, 2015 and 2016)].
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- Asesiad o Gyflwr y Cimwch Afon Crafanc Wen Austropotamobius pallipes yn Ardal Cadwraeth Arbennig Afon Gwy yn 2014-2016.
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Sampling techniques included a combination of manual searching and trapping, and were undertaken by competent surveyors.
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Rogers, D. & Watson, E. (2017), Assessment of the condition of the white-clawed crayfish Austropotamobius pallipes in the River Wye Special Area of Conservation in 2014-2016, NRW Report No. 187, 163pp, Natural Resources Wales, Bangor.
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[A] The final report in Microsoft Word and Adobe PDF formats. [B] Species records, which are held on the NRW Recorder 6 database.
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Sampling techniques included a combination of manual searching and trapping, and were undertaken by competent surveyors.
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Assessment of the condition of the white-clawed crayfish Austropotamobius pallipes in the River Wye Special Area of Conservation in 2014-2016
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