Llyn Tegid Hydroacoustic Surveys and Gwyniad Translocations 2004-2009

The gwyniad (Coregonus lavaretus) population of Llyn Tegid has been considered, for a number of years, to be threatened by deteriorating environmental conditions, particularly those associated with eutrophication. This dataset contains the results of a project established in 2004 to carry out translocations, hydroacoustic surveys, and the measurement of environmental variables. The purpose of this data collection was to assess the implications for the status of gwyniad (Coregonus lavaretus) and its habitat in Llyn Tegid.

The objectives of the project included both conservation actions and further research, including the establishment of a refuge population in Llyn Arenig Fawr. Surveys were carried out annually from 2004 to 2009. Following an unsuccessful translocation attempt in 2003, three successful translocations took place in early 2005, 2006, and 2007. A full fish population survey of the recipient site, Llyn Arenig Fawr, was undertaken in 2009.

Identifier: NRW_DS101834

Alternative Title

Gwyniad Hydroacoustic Survey 2003 - 2009 - CCW Science Report 903 - Countryside Coucil for Wales CCW000800000000C
Gwyniad Hydroacoustic and Gill netting survey of Llyn Arenig Fawr 2009 - CCW Science Report 904 CCW000800000000D
Llyn Arenig Fawr Hydroacoustic Gwyniad Surveys

Metadata Language: English

Lineage: Hydroacoustic surveys and measurements of environmental variables, including temperature, oxygen profiles, and Secchi disk readings, have been carried out annually since 2004 (with the exception of Secchi disk readings in the 2008 survey). In 2005, an analysis of historic lake data in the context of gwyniad spawning requirements was also undertaken.

The methodology followed the standardised survey and monitoring protocol for the assessment of whitefish (Bean, 2003; JNCC, 2005), with two minor deviations. Firstly, rather than using the target strength-to-fish-length relationship described by Foote (1987), the relationship given by Love (1971) was used to allow wider comparison. Secondly, a vessel speed of 2.0 m s⁻¹ was adopted as the general target mean speed rather than as an absolute upper limit.

Translocation attempts involved seine netting conducted after dark. Stripping was performed on the morning following sampling, and the volume of eggs was determined. Viable gwyniad were returned alive to the lake. Eggs were transported to Llyn Arenig Fawr and introduced into incubation boxes. A fish population survey at the recipient site was undertaken using hydroacoustic methods and gill netting.

Additional Information: Rivers Ecologist, Marine and Freshwater Science Group, NRW Data collected under project number FC 73-02-304. The species records which form part of this dataset are available to download from the NBN Gateway as part of a larger packaged species dataset.

Dataset Reference Date (Publication): 2009-12-31

Temporal Extent

Begin date: 2004-08-05

End date: 2009-07-31

Topic category

Biota

Owner

Natural Resources Wales (NRW) -

Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales

http://naturalresources.wales/?lang=en

Originator

Centre for Ecology and Hydrology (CEH) -

Environment Centre Wales, Deiniol Road, Bangor, Gwynedd, LL57 2UW, Wales

http://www.ceh.ac.uk/

Extent

Geographic Extent: Wales (WLS)

Geographic Extent: GWYNEDD - GWYNEDD

Map representing the geographic extent of the dataset

Distribution

Format Type and Description

Delimited ( Unknown )

Specification

Echoview analysis data (*.csv); lake level data (2005 survey).
Binary ( Unknown )

Specification

Raw echo sounder data (*.dt4 format).
Text or Plaintext ( Unknown )

Specification

Oxygen and temperature profiles; Secchi depth measurements; hydroacoustic transect lengths; back-calculated under-yearling gwyniad lengths.
Documents ( Unknown )

Specification

CCW Contract Science Reports 903 and 904 (PDF and Microsoft Word formats).
Image ( Unknown )

Specification

Translocation photographs.
Movie ( Unknown )

Specification

Translocation video clips.
Database ( Unknown )

Specification

Archived survey and translocation data held under Project Numbers 29, 154, 194, 200, 226 and 227; Media Numbers 169, 232, 468, 539, 595 and 952. Species data also stored in Recorder 6.

Data quality

Quality Scope: Dataset

Conformity: Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services
Explanation: This dataset has not been assessed for conformance to the referenced INSPIRE regulation.
Degree: false

Lineage: Hydroacoustic surveys and measurements of environmental variables, including temperature, oxygen profiles, and Secchi disk readings, have been carried out annually since 2004 (with the exception of Secchi disk readings in the 2008 survey). In 2005, an analysis of historic lake data in the context of gwyniad spawning requirements was also undertaken.

The methodology followed the standardised survey and monitoring protocol for the assessment of whitefish (Bean, 2003; JNCC, 2005), with two minor deviations. Firstly, rather than using the target strength-to-fish-length relationship described by Foote (1987), the relationship given by Love (1971) was used to allow wider comparison. Secondly, a vessel speed of 2.0 m s⁻¹ was adopted as the general target mean speed rather than as an absolute upper limit.

Translocation attempts involved seine netting conducted after dark. Stripping was performed on the morning following sampling, and the volume of eggs was determined. Viable gwyniad were returned alive to the lake. Eggs were transported to Llyn Arenig Fawr and introduced into incubation boxes. A fish population survey at the recipient site was undertaken using hydroacoustic methods and gill netting.

Keywords

GEMET - INSPIRE themes, version 1.0

Species distribution

Type: Theme

Citation

Date (Publication): 2008-06-01

Code: geonetwork.thesaurus.external.theme.httpinspireeceuropaeutheme-theme

Keywords

NRW Thesaurus

oxygen profile
marine and freshwater inventory
gwyniad (freshwater whitefish)
hydroacoustic
Llyn Tegid
coregonus lavaretus
temperature profile
Llyn Arenig Fawr
secchi depth

Type: Theme

Citation

Date (Publication): 2026-08-27

Code: geonetwork.thesaurus.local.theme.converted_nrw-keywords

Code: British National Grid (EPSG::27700)

Content Information

NRW Profile

Custom Elements

NRW Related Title: Gwyniad translocation project 2004-05 : hydroacoustic survey of Llyn Tegid

NRW Related Title: Llyn Tegid hydroacoustic surveys 2005

NRW Related Title: Llyn Tegid hydroacoustic surveys 2006

NRW Related Title: Llyn Tegid hydroacoustic surveys 2007

NRW Related Title: Llyn Tegid hydroacoustic survey 2008

NRW Related Title: Gwyniad translocation project 2004-05 : translocation attempt

NRW Related Title: Llyn Tegid gwyniad translocation advice 2005-2006

NRW Related Title: Llyn Tegid gwyniad translocation advice 2006-2007

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 2008. 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.

Attribution Statement

Licence

Other constraints: Open Government Licence

Metadata

File Identifier: 4f4c4942-4343-5764-6473-313031383334 XML

Metadata Language: English

Parent Identifier: Freshwater Gwyniad (Coregonus lavaretus) Species Survey Data
NRW_DS116344

Resource type: Dataset

Metadata Date: 2026-09-29T13:49:00.998Z

Metadata Standard Name: NRW

Metadata Standard Version: 1.0

pointOfContact

Master Reference Data Team -

Natural Resources Wales, Maes y Fynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW

http://naturalresourceswales.gov.uk/splash?orig=/

Publishing Body

Access the portal

Full access to the portal and metadata.

Llyn Tegid Hydroacoustic Surveys and Gwyniad Translocations 2004-2009

Identification

Temporal Extent

Extent

Extent

Distribution

Distribution

Quality

Data quality

Keywords

Keywords

Citation

Keywords

Citation

Spatial Reference System

Content

Content Information

NRW Profile

Custom Elements

Constraints

Constraints

Limitations on Public Access and Use

Access Constraints Directive

Access Constraints Text

Use Constraints

Attribution Statement

Licence

Metadata

Metadata

Publishing Body