2003 - 2004 Centre for Environment, Fisheries & Aquaculture Science (Cefas) North Sea Cod Spawning - Plankton Survey
PLACES
Ichthyoplankton data from a survey carried out by RV Corystes as part of an internationally co-ordinated series of surveys to assess the cod and plaice spawning areas in the North Sea, organised by the Planning Group on North Sea Cod and Plaice Egg Surveys (PGEGGS). The data consists of the numbers of fish eggs and larvae identified at each sampling site, along with associated positional data and volumes filtered.
dataset
CEFASb49b2e0f-5b8e-444a-be06-c260273bb862
http://www.cefas.co.uk/
eng
OGP
urn:ogc:def:crs:EPSG::4326
revision
2011-03-25
publication
2008-06-01
-4.5
9
60.5
52
revision
2010-05-18
2003-04-01
2004-03-31
publication
2019-10-29
notPlanned
Samples were collected on RV Corystes using a Gulf VII 53cm high speed tow net, conical nosecone with 40 cm diameter opening, 270 um mesh main net, Valeport flowmeters and Guildline logging system. Sampler deployment:The sampler was deployed in a double oblique tow from the surface to within 2 m of the seabed. Veering and hauling speeds were manually adjusted to ensure that each depth band was sampled equally. At shallow stations, multiple double oblique dives were necessary to enable a sufficient volume of water to be filtered. A minimum sampler deployment time of 15 minutes was aimed for. On recovery, the net was carefully washed down and the sample collected from the end bag. Each sample was then fixed using buffered formaldehyde solution and transported to the participating laboratories for sorting and identification.Sample analysis:Fish eggs and larvae were picked out from all samples by eye and, whenever practicable, the whole sample was sorted. However sub-sampling was at times necessary. Sub-sampling was carried out using a Folsom splitter. Fish larvae were readily identified unless they had been badly damaged during collection or were prematurely hatched. For some groups such as the sandeels (Ammodytidae) and the group of Gadidae commonly called rocklings, individuals were not identified to the species level. Fish eggs were initially split into three groups on the basis of the presence or absence of oil globules. Those containing either a single or many oil globules could usually be identified to the species level. Eggs with no oil globules were more difficult to identify. Some of these species such as cod (Gadus morhua), sprat (Sprattus sprattus), long rough dab (Hippoglossoides platessoides), dragonet (Callionymus spp.) and plaice (Pleuronectes platessa) were identified because of their size or unique features. Unidentified eggs in this group were recorded as egg diameters. Data storage: The raw data were stored in an Access database. The various data files were stored in the database in a series of tables linked by having the content of certain fields in common. All routine calculations, calibration changes and conversions were carried out in the database. The data tables (but not queries) have now been extracted into comma separated variable files. Plankton data are normally expressed as either number of organisms per m3 or per m2. These are calculated from the volume of water filtered (derived using regression co-efficients calculated for different flowmeters). Number per m3 is obtained by dividing the numbers per sample by the volume filtered, and number per m2 of sea surface is obtained by multiplying the number per m3 by the mean total or sampled depth during a deployment.
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
pointOfContact
2019-10-29T10:09:44