1982 - 1982 Centre for Environment, Fisheries & Aquaculture Science (Cefas) Irish Sea Plankton Survey - RV Clione 06/82
<span style="font-family: 'Trebuchet MS','sans-serif'; color: black;">...</span>
dataset
http://data.cefas.co.uk/#/View/2530/
function: order
CEFAS01b3e698-29e4-4c69-9683-820e65e50f8b
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
-7
-3
54.75
53
revision
2010-05-18
1982-04-26
1982-05-14
publication
2020-01-29
notPlanned
**Sampling:** Plankton samples were taken with a modified version of the Lowestoft 76 cm diameter high-speed sampler. This was modified by increasing the overall length from 2.13 m to 2.75 m and by fitting a conical nose cone with an aperture of 40 cm diameter instead of a hemispherical one. The sampler was fitted with a 270 µm aperture mesh resulting in an open area to nose cone aperture ratio of 12:l. The sampler was deployed at a nominal speed of 2.5 m s <sup>...</sup> ¹ 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. On recovery, the net was carefully washed down and the sample collected from the end bag. Each sample was then fixed in a 4% (w/v) formaldehyde solution and returned to the laboratory for analysis. The sampler, towed on a multi-cored electric cable, was fitted with both internal and external electronic flowmeters. Output was logged directly using a deck unit and used to calculate the volume of water filtered on each deployment. The flowmeters were calibrated in situ on the sampler using a circulating water channel. Under normal operating conditions, the sampler body accepts over ninety per cent of the theoretical volume of water offered to it at 2.5 m s <sup>...</sup> ¹. Even under severe clogging, fifty per cent of this volume would still be filtered. The plankton sampler was fitted with a Guildline CTD sensor package which was used to continuously monitor temperature and salinity throughout the deployment. The CTD data were observed on a deck unit and recorded as depth profiles on continuous chart records. In 1982 an in-house CTD system was used.This was changed from 1985 onwards to the Guildline CTD, matching the one on the plankton sampler. CTD systems were routinely calibrated at the beginning and end of each survey. The levels of precision (as the standard deviation about the mean based on the manufacturer's calibrations) were ± 0.04 psu for salinity and **±** 0.02 ̊C for temperature. **Plankton sample sorting and sub-sampling** : Initially the samples were sorted only for the larvae of *Nephrops norvegicus* . 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. Aliquots were removed using a 20 or 30 ml measured scoop. 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 unique size or special features. Unidentified eggs in this group were recorded as egg diameters. **Data analysis and data storage (original): ** The raw data were stored on a customised database, initially using INGRES version 5, then transferred at a later date to Access version 2. The various data files were stored on 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 on the database. The data has now been extracted into comma separated variable files. Plankton data are normally expressed as either number of organisms per m3 or per m2. The number per m3 is obtained by dividing the numbers per sample by the volume filtered, calculated from the sampler flowmeters. Number per m2 is obtained by multiplying the number per m3 by the mean sampled or total 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
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
2020-01-29T12:54:42