1996 - 2012 Centre for Environment, Fisheries & Aquaculture Science (Cefas) Nephrops underwater TV Surveys in the North Sea (video data and database)
Nephrops burrow counts
Underwater TV (UWTV) surveys dataset, used as basis of the Nephrops ( *Nephrops* *norvegicus* ) assessment to develop fishery independent indicators of stock size, exploitation status and catch advice. The standard methodology involves the use of a sledge mounted camera to film the seabed at a fix grid of stations conducting TV tows for 10 minutes. Data has been collected twice a year between 1997 to 2002 (Spring and Autumn) and once a year since 2003 (autumn). Dataset holds data from two areas of the North Sea (Farn Deeps-FU6 (1996 to 2012) and Botney Gut/Silver Pit-FU5 (2010 to 2012)).
dataset
CEFAS1171372a-92df-4122-8c75-a9b744d2cd47
http://www.cefas.co.uk/
eng
OGP
urn:ogc:def:crs:EPSG::4326
biota
revision
2011-03-25
publication
2008-06-01
publication
2008-06-01
-1.5
4
55.75
53.5
revision
2010-05-18
revision
2010-05-18
1996
2012-09-18
publication
2016-07-14
annually
The full dataset consists of approximately 160+ VHS tapes (1996 to 2002) and 260+ DVD discs (2003 to present) plus additional back-up tapes. The DVD discs are kept for reference and quality-control purposes at Cefas, Lowestoft, for a period of 5 years, after which they are disposed of. The VHS tapes are now obsolete but will be retained until January 2017 at which time they will be disposed of. Material can be made available upon request (please contact data steward for more information). Positional data and Nephrops burrow counts have been stored in a shellfish access database since 1996. In line with SGNEPS (Study Group Nephrops) recommendations all scientists are trained/re-familiarised using training material and validated using reference footage (measured by Linn’s concordance correlation coefficient (CCC)) prior to recounting each survey footage. A limit of 0.5 is used to identify counters who need further training. On completion of this process, all survey recounts are conducted, as blind counts, by two persons during the survey. Here, the number of Nephrops burrow systems and the activity in and out of the burrows are counted by each minute block (for 7 clear minutes). In cases where the field of view became obscured by cloud, the number of seconds obscured are recorded and all minute blocks with more than 20 seconds obscured are rejected for analysis. After all counts completed again the Linn’s CCC is again applied to check which stations needed to be revisited and were a 3rd or 4th counter needed to be added. Whilst reviewing the videos, the visibility, ground type, trawl marks, occurrence of bio-fauna, ground contact of the sledge, cloud and any other interference is recorded during each one-minute intervals, using a classification key. Example footage and a training presentation are available via the metadata record entitled 'Nephrops underwater TV Surveys - VHS and DVD footage'. For sediment analysis data of these grounds please contact the Cefas sedimentology team. For acoustic data recorded in these grounds (multibeam and backscattered data) please contact Cefas MIST team.
Public data (Crown Copyright) - Open Government Licence Terms and Conditions apply
Public data (Crown Copyright) - Open Government Licence Terms and Conditions apply
Data Manager
Centre for Environment, Fisheries & Aquaculture Science
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
+44 (0)1502 562244
originator
Data Manager
Centre for Environment, Fisheries & Aquaculture Science
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
+44 (0)1502 562244
custodian
Data Manager
Centre for Environment, Fisheries & Aquaculture Science
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
+44 (0)1502 562244
pointOfContact
2016-07-14T12:28:23