SAC Monitoring: Afon Tywi Shad Egg Survey (2013 and 2014)
The Afon Tywi is designated as a Special Area of Conservation (SAC) for several features including twaite shad (Alosa fallax) and allis shad (Alosa alosa). Shads are migratory members of the Clupeidae (herring family) that ascend rivers to spawn in late spring. In Britain, significant populations of shad spawn in the Rivers Severn, Usk, Wye and Tywi. The populations of both species are threatened in Europe mainly due to obstructions to migration and issues surrounding water quality. The aim of this data collection was to contribute towards the assessment the condition of the shad population in the Afon Tywi SAC based on 2013 and 2014 egg surveys. The objectives of this study are to: 1) Conduct a shad egg survey on the Afon Tywi in 2013 and 2014. 2) Analyse and present the results for spawning distribution of the population attribute only. 3) Use the data obtained from the genetic analysis of shad egg tissue to give additional context to the above analysis. 2013 Shad eggs were present at seven of 13 survey sites (54 percent). Each of the 12 survey sites were visited once. The egg sample size ranged from 1 to 100 plus eggs. The downstream limit of spawning was Tidal limit (site 16) and the upstream limit was Manordeilo (site 11). A total of 177 plus eggs were recorded. The identification of shad eggs were confirmed through genetic analysis at two of the three selected sample sites. 2014 Shad eggs were recorded at eight of the 14 survey sites (57 percent). Seven of the sample sites were visited twice (54 percent) and four sites were visited three times (29 percent). The 14 sites were surveyed between 16 May and 11 Junes over 6 days by 13 surveyors. Purpose of data capture:
- Identification
- Extent
- Distribution
- Quality
- Keywords
- Spatial Reference System
- Content
- Constraints
- Maintenance
- Metadata
Identification
- Identifier
- NRW_DS115889
- Metadata Language
- English
- Lineage
-
The Hillman method is quantitative which involves counting shad eggs in 25 kick samples per site was used. In 2013, the Hillman methodology was modified to a minimum of 10 kick samples were undertaken at each site with the number of eggs found in each kick recorded. If 20 or more shad eggs were recorded after 10 kicks the survey was terminated, however, if fewer than 20 shad eggs were recorded, kick sampling continued either until 20 eggs were found or 25 kick samples had been completed. A standard macroinvertebrate hand net (250 micrometre) was used to collect material dislodged by kicking (or shuffling) upstream of the net for approximately 15 seconds. The net was checked for the presence of shad eggs after each kicking interval and any detritus or channel substrate removed before kicking was resumed. The number of shad eggs were counted after each kick sample and recorded on the field sheet. Sampling started at the downstream end of the potential spawning site to prevent the possible re-recording of eggs dislodged in previous kicks. If possible, sites where no eggs were found were re-visited at a later date in the spawning season; however, this was dependant on weather conditions and availability of the survey team. The JNCC have published generic guidance on Common Standards Monitoring Guidance for Freshwater Fauna outlining the attributes (mandatory and discretionary) and targets for monitoring freshwater fish. These include targets for shad population, flow, water quality and river morphology. Assessments are made on a 6 year cycle. NRW are currently in the third monitoring cycle (2013-2018). Both allis and twaite shad have been reported as unfavourable overall in the first (2001-2006) and second (2007-2012) reporting cycles.
- Additional Information
-
Freshwater Monitoring Co-ordinator, Marine & Freshwater Ecosystems Group. Also see associated NRW evidence report: Afon Tywi SAC shad egg surveys 2013 & 2014. Garrett HM, Thomas Rh, & Hatton-Ellis TW. Report No. NRW Evidence Report No. 48 Date: February 2015
- Dataset Reference Date (Publication)
- 2015-02-01
Extent
Extent
- Geographic Extent
- SIR GAERFYRDDIN - CARMARTHENSHIRE
))
Distribution
- Format Type and Description
-
-
Documents
()
- Specification
-
[A] A report in .doc and .pdf format (see CCW Document Archive Ffynnon NRW-13-071629) [B] A series of GIS layers in MapInfo .Tab format on which the maps are based [C] A set of spreadsheets for the raw data and worked up data in xls format ( CCW Document Archive NRW-13-054339, NRW-13-054417) [D] Field notes in paper format (held in in Llandeilo office). File reference unknown. (Copies held in Evidence and Analysis Team, Maes y Ffynnon, Bangor) [E] Data is to be entered into Recorder 6.
-
Documents
()
Quality
Data quality
- Quality Scope
- Dataset
- Lineage
-
The Hillman method is quantitative which involves counting shad eggs in 25 kick samples per site was used. In 2013, the Hillman methodology was modified to a minimum of 10 kick samples were undertaken at each site with the number of eggs found in each kick recorded. If 20 or more shad eggs were recorded after 10 kicks the survey was terminated, however, if fewer than 20 shad eggs were recorded, kick sampling continued either until 20 eggs were found or 25 kick samples had been completed. A standard macroinvertebrate hand net (250 micrometre) was used to collect material dislodged by kicking (or shuffling) upstream of the net for approximately 15 seconds. The net was checked for the presence of shad eggs after each kicking interval and any detritus or channel substrate removed before kicking was resumed. The number of shad eggs were counted after each kick sample and recorded on the field sheet. Sampling started at the downstream end of the potential spawning site to prevent the possible re-recording of eggs dislodged in previous kicks. If possible, sites where no eggs were found were re-visited at a later date in the spawning season; however, this was dependant on weather conditions and availability of the survey team. The JNCC have published generic guidance on Common Standards Monitoring Guidance for Freshwater Fauna outlining the attributes (mandatory and discretionary) and targets for monitoring freshwater fish. These include targets for shad population, flow, water quality and river morphology. Assessments are made on a 6 year cycle. NRW are currently in the third monitoring cycle (2013-2018). Both allis and twaite shad have been reported as unfavourable overall in the first (2001-2006) and second (2007-2012) reporting cycles.
Keywords
Keywords
- Type
- Theme
Citation
- Date (Publication)
- 2008-06-01
Keywords
- NRW Thesaurus
-
- allis shad
- alosa alosa
- alosa fallax
- twaite shad
- river Tywi (afon Tywi)
- Special Areas of Conservation (SAC) - SAC monitoring
- Special Area of Conservation Monitoring
- Type
- Theme
Citation
- Date (Publication)
- 2023-12-31
Spatial Reference System
Content
Content Information
NRW Profile
Custom Elements
- NRW Related Title
-
Afon Tywi SAC shad egg survey 2012
Constraints
Constraints
Limitations on Public Access and Use
- Restriction type
- Other restrictions
Access Constraints Directive
- Limitations
- no limitations
Access Constraints Text
- Other constraints
-
There are no access restrictions to this data. NRW may release, publish or disseminate it freely.
Use Constraints
- Use constraints type
- Other restrictions
- Other constraints
-
© CNC/NRW, 2015. There are no use restrictions on this data. Recipients may re-use, reproduce, disseminate this data free of charge in any format or medium, provided they do so accurately, acknowledging both the source and NRW's copyright, and do not use it in a misleading context. It is the recipient's responsibility to ensure the data is fit for the intended purpose, that dissemination or publishing does not result in duplication, and that it is fairly interpreted. Advice on interpretation should be sought where required. To avoid re-using old data, users should periodically obtain the latest version from the original source.
Metadata
Metadata
- File Identifier
- 4f4c4942-4343-5764-6473-313135383839 XML
- Metadata Language
- English
- Parent Identifier
-
SAC Monitoring: Afon Tywi Shad Egg Survey (2012)
NRW_DS115312
- Resource type
- Dataset
- Metadata Date
- 2024-05-31T09:43:03.173Z
- Metadata Standard Name
- NRW
- Metadata Standard Version
-
1.0