2010 - 2010 Centre for Environment, Fisheries & Aquaculture Science (Cefas) Cod Tagging in the North Thames Region 2009/10 - Fisheries Science Partnership
FSP Cod tagging north Thames region
The FV Harvester was chartered between February and March 2010 as part of the FSP North Thames cod tagging programme. The aim of the programme was to investigate spatial movements of adult cod, a species known to aggregate annually between January and March (during spawning) in the North Thames and Shipwash area. In all, 233 cod were captured for tagging purposes during the study
dataset
http://data.cefas.co.uk/#/View/640/
function: order
CEFAS9ddfb55b-14ee-4219-8149-509d95f814a7
http://www.cefas.co.uk/
eng
OGP
urn:ogc:def:crs:EPSG::4326
biota
revision
2011-03-25
publication
2008-06-01
-0.5
3
52.25
50.5
revision
2010-05-18
2010-02-01T00:00:00.000Z
2010-03-31T00:00:00.000Z
publication
2017-02-14
notPlanned
Methods Field study design The field study was designed to catch and tag ~300 mature adult cod (>50 cm long, based on maturity ogives derived from International Bottom Trawl Survey data collected between 1977 and 2005 (ICES, 2005)) with external plastic T-bar anchor tags, and ~15 DSTs. In all, 12 days at sea were split into three trips between January and March 2010 to coincide with the north Thames spawning aggregation of cod. Areas fished were based upon years of local knowledge and experience of fishermen catching cod within the north Thames region, between West Mersea and Shipwash, within 10 miles of the coast of East Anglia. The field study detailed in the DOP had to be modified during the course of fishing operations owing to disruption caused by bad weather. Planned dates and sailings had to be adjusted to coincide with limited periods of good weather, and with knowledge of a lack of sufficient numbers of cod on the inshore grounds. The extreme cold weather and unusually high run-off of snow-melt and freshwater throughout January and February 2010 meant that adult cod seemed to aggregate farther offshore (~30 miles) in deeper water, with only a limited number appearing to enter estuarine waters (based on local fisheries knowledge and catch rates during this period). Fishing vessel, gear and activity The FV Harvester is an under 10 m bottom trawler with a 115 kW engine. The trawl gear used throughout the field study was a 18 m (10 fm) Boris Box Trawl with 27 m (15 fm) sweeps, a 20 cm ( 8”) mesh size entry, 10 cm (4”) mesh in the wings, 120 mm meshes in the sleeve and codend, 30 cm (12”) hopper discs and No.4 Bison doors. Fishing activity per day was aimed to allow for approximately five variable short bottom tows, to ensure greatest survival and fitness of mature cod. The net was shot over the stern of the vessel and towed for 1–1½ h before being hauled slowly to the surface to avoid rupture of the swimbladder of any cod caught. The net was brought aboard, the codend emptied into 1000-l deck tanks of seawater, and manually sorted for mature cod. After being hauled aboard and emptied, the net was again shot, to allow continued fishing activity while any suitable cod from the previous catch were measured (for length and weight), sexed (where possible), tagged and released. Tagging procedure Between February and March 2010, 217 mature adult cod were tagged and released primarily within ICES rectangle 32 F1 of the North Thames Estuary. Cod in seemingly fit condition were placed into separate 1000-l deck tanks prior to being tagged, to assess their fitness and state of inflation of the swimbladder. All cod that were caught were in very good condition, and all were suitable for subsequent release. However, despite being hauled onto the deck slowly, most cod still showed overinflation of their swimbladder, which required deflation with a hollow needle in order for the cod to retain natural buoyancy within the deck tanks. Cod suitable for tagging (length >45 cm) were measured, weighed and placed into a „V-shaped‟ channel foam block which was kept wet with seawater. Then, a wet cloth was placed over the head and operculae of the fish before they were double-tagged with an external T-Bar anchor tag. In addition, 14 cod were tagged with internal DSTs. Those cod were first anaesthetized in a shallow (20 cm) bath containing 2-phenoxy-ethanol (0.5 ml l-1), before being placed on the „V-shaped‟ foam block with a constant flow of seawater pumped across the gills. The DST was then surgically implanted into the peritoneal cavity (details in Righton et al., 2006). A spaghetti tag attached to the DST was then placed through the lateral body wall using a curved needle. Two cod captured were unsuitable for tagging (both mature females in poor condition, due to net damage and air in body cavity), and were therefore biologically sampled on deck. For the first 100 cod, a small fin-clip was taken from the third dorsal fin and preserved in 95% ethanol in a 5 ml Eppendorf container. Finally, all cod were placed into a recovery tank before release. <span style="font-family: Calibri;">...</span> <span style="font-family: Calibri;">...</span> <span style="font-family: Calibri;">...</span>
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
2017-02-14T10:26:52