Irish Sea Plankton Survey - RV Clione 06/85
Between March and June of 1982 and 1985 a series of plankton surveys was carried out in the western Irish Sea to determine the distribution and abundance of the larvae of *Nephrops norvegicus* L. Plankton samples were collected at each site on a planned survey grid. In addition to Nephrops larvae, fish eggs and larvae were also analysed. The data described here consists of the numbers of Nephrops larvae and fish eggs and larvae identified from the main net samples collected on the survey in May 1985, along with associated positional and ancillary data and volumes filtered.
dataset
https://data.cefas.co.uk/view/2533
name: Cefas Data Portal
description: The Cefas Data Portal contains metadata records and data sets available to download and connect to in support of our commitment to open science. Data is available in the following formats: CSV, ESRI Shapefile. The data can also be accessed via the WFS and WMS protocols.
function: download
CEFAS2533
https://data.cefas.co.uk
eng
biota
revision
2011-03-25
publication
2008-06-01
publication
2008-06-01
revision
2010-05-18
publication
2012-01-11
publication
2012-01-11
-7.00
-2.50
54.75
51.75
1985-05-07
1985-05-29
publication
2013-11-21
revision
2023-10-31
creation
2013-06-26
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 12:1. The sampler was deployed at a nominal speed of 2.5 m s -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-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 1982 and 1985 samples were sorted only for the larvae of *Nephrops norvegicus*. The samples were subsequently analysed for fish eggs and larvae, with the exception of the third survey in 1985 from 19-26 May, which had an incomplete coverage of the area. The samples taken in 1987,1988 and 1989 were sorted for all species. 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 ( *Callionymu*s 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 total or sampled depth during a deployment.
publication
2013-12-10
false
See the referenced specification
publication
2010-12-08
true
See the referenced specification
Unknown
Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory (CEFAS)
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
originator
Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory (CEFAS)
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
custodian
Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory (CEFAS)
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
distributor
Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory (CEFAS)
owner
Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory (CEFAS)
Cefas Lowestoft Laboratory
Pakefield Road
Lowestoft
NR33 0HT
UK
pointOfContact
2023-10-31T11:23:04