Identification

Title

2007 - 2009 Centre for Environment, Fisheries & Aquaculture Science (Cefas) Northern North Sea Saithe (and Cod) Survey 2008/09 - Fisheries Science Partnership

Alternative title(s)

FSP Northern North Sea Saithe

Abstract

A programme set up in 2007/2008 which described the fine scale distribution and abundance in time and space of saithe (primarily) and cod, including specific information on the 2005 and 2006 year-classes of saithe, and the 2006 and 2007 year-classes of cod.

Resource type

dataset

Resource locator

http://data.cefas.co.uk/#/View/18215/

function: order

Unique resource identifier

code

CEFAScdfa14e9-4509-4e81-a30e-ebe06a998113

codeSpace

http://www.cefas.co.uk/

Dataset language

eng

Spatial reference system

authority code

OGP

code identifying the spatial reference system

urn:ogc:def:crs:EPSG::4326

Classification of spatial data and services

Topic category

biota

Keywords

Keyword set

keyword value

Keyword set

keyword value

originating controlled vocabulary

title

SeaDataNet P021 parameter discovery vocabulary

reference date

date type

revision

effective date

2011-03-25

Keyword set

keyword value

originating controlled vocabulary

title

GEMET - INSPIRE themes, version 1.0

reference date

date type

publication

effective date

2008-06-01

Geographic location

West bounding longitude

-5

East bounding longitude

9

North bounding latitude

62

South bounding latitude

57

Extent

Extent group

authority code

title

SeaVoX Vertical Co-ordinate Coverages

reference date

date type

revision

effective date

2010-05-18

code identifying the extent

Temporal reference

Temporal extent

Begin position

2007-05-01T00:00:00.000Z

End position

2009-03-30T00:00:00.000Z

Dataset reference date

date type

publication

effective date

2017-02-14

Frequency of update

011

Quality and validity

Lineage

Methods The fishing vessel and area fished The study was conducted between May 2007 and March 2009 (herein referred to as the study period) on board the commercial fishing vessel MFV “Farnella” (length overall, 40.2 m; GRT 667; main engine, 1880 kW). “Farnella” uses a trawl typical of the northern North Sea saithe fishery (headline height 4 m, door spread 110–115 m codend mesh >110 mm, tow speed 4 knots). Throughout, fishing took place in the northern North Sea, but for the most part focused on ICES Division IVa). Data collection Self sampling Estimating fish numbers and weights The skipper and crew were asked to provide estimates of the weight and number of retained and discarded cod and saithe of each size grade for every haul. At the end of each haul, fishroom staff provided the wheelhouse a tally recording the number of baskets per grade of cod and saithe caught. Baskets were estimated at 45 kg, and the numbers of fish in each basket were assessed regularly (to take into account the seasonal and spatial variations of fish condition). Biotic and abiotic measurements All cod were caught in every haul were measured, and a minimum of 100 saithe per size grade were measured per trip. When necessary (large hauls), saithe numbers were raised to haul level as a proportion of the total catch, using volume-based raising factors. All fish were measured to the nearest centimetre below (total length). Environmental conditions (sea state, wind strength/ direction) and physical conditions (depth, position, haul-duration and gear properties) were recorded along with the biological data. Observer sampling Three observer trips were conducted throughout the study period. The first observer trip, in May 2007, was used to train the skipper and crew of the “Farnella” in sampling methods. The second and third observer trips were used to maintain the standards applied from the start (there was skipper and crew turnover) and particularly to ensure that the self-sampling was of a very high standard. These second two observer trips were carried out in the first quarters of 2008 and 2009. Information collected from the trained observers was used to validate the data provided by the vessel and to provide a more detailed overview of the fishery with respect to bycatch and discards. Fish age determination A total of 29 000 fish otoliths was removed at sea by observers and from fish landed to fish markets. Of these, 15 500 were from cod and 13 500 from saithe. All otoliths were extracted from fish that had been caught in ICES area IVa between April 2007 and March 2009 (the study period covered by this report). Otoliths were mounted, sectioned, stained, read, and re-read for quality control purposes, according to the protocols of Cefas and Marine Scotland - Marine Laboratory. Data analysis Data handling Trip, haul, length, catch and age data were entered onto a MS access database. All data entered were cross-checked against the paperwork and quality-controlled for inaccuracies. Data were handled using SPSS V17 statistical software, charts were produced using Sigmaplot V10.0, and maps were created in MapInfo V7.8. Converting fish length into fish ages Age-at-length data collected from the 15 500 cod and 13 500 saithe that were aged were used. Data were collected throughout the year to take into account length variations of a growing age class. At a given length in any quarter, fish age will vary. For example, in quarter 3 of 2007, 49 cod of the 70-cm length class were aged as between one and four years old, so when one 70-cm cod was observed and measured in quarter 3, it was aged proportionally to what was observed in the population. Each fish length has a different combination of proportions at a given age. If more than one fish was observed at a given length, then the number at length was multiplied by the proportion at age to give the estimated numbers at a given age. Age-length keys (ALKs) applied to this analysis are area- (ICES IVa), species- (cod or saithe) and season-specific (quarters 1, 2, 3 and 4). Sex is not taken into account. When a fish length could not be matched with a length that had been aged in a particular quarter, then seasonality was removed and an aggregated ALK for the whole year was used. This occurred in <2% of the >75 000 fish measured. Generating an age-category key Haul data are presented in numbers of fish caught by category. In order to make use of this information and to evaluate the numbers-at-age of fish caught at a particular haul location, we need to understand the age spread of a particular category. Fishermen were asked to record the category of the fish measured. With each measurement we can assess the age of the fish, so an area, species and season age-category key can be generated. For example, in quarter 3 of 2007, an estimated 1 990 category 4 cod were caught. These were aged between 2 and 6 years old, so when a category 4 fish was caught (now disregarding length information) we applied the same method as an ALK and aged it proportionally using an age category key (ACK). For example, If 1000 category 4 cod were caught in a particular haul, we would estimate 533 to be age 2 (1000 x 0.533), 398 to be age 3 (1000 x 0.398), 66 to be age 4, etc. Calculating catch per unit effort The total numbers of fish caught each month (by species) were divided by the total haul duration to determine the numbers of fish caught per hour, or the catch per unit effort (CPUE). This unit allowed the catch data to be standardised and used for comparative analysis. Summary The Northern North Sea Saithe (and Cod) FSP was established in response to an industry- and science-perceived absence of realistic data on the 2004 and 2005 year classes of saithe and the 2005 and 2006 year classes of cod. The 2005 and 2004 year classes of saithe (4 and 5 year olds) are of particular interest because they were predicted to contribute significantly to projected landings in 2008 and subsequently to contribute to the spawning-stock biomass of the species in 2009. This study uses data collected at haul level by fishermen aboard the commercial fishing vessel MFV “Farnella” over a two-year period. Throughout, fishing was widespread in the northern North Sea, but for the most part was focused on ICES Division IVa. The skipper and crew were trained in sampling techniques prior to collecting the data. and all information sent ashore was checked regularly. Observer-accompanied trips were also carried out to ensure a high standard of data quality. Between May 2007 and March 2009 (the study period) MFV “Farnella” embarked on 51 commercial fishing trips in the northern North Sea (ICES IVa), hauled 1154 times, and caught 3.3 million saithe (Pollachius virens) and 51 000 Atlantic cod (Gadus morhua). Of the fish caught, the crew measured most of the cod (48 772) and 26 518 saithe (75 290 in total).

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Public data (Crown Copyright) - Open Government Licence Terms and Conditions apply

Constraint set

Limitations on public access

Public data (Crown Copyright) - Open Government Licence Terms and Conditions apply

Responsible organisations

Responsible party

contact position

Data Manager

organisation name

Centre for Environment, Fisheries & Aquaculture Science

full postal address

Cefas Lowestoft Laboratory

Pakefield Road

Lowestoft

NR33 0HT

UK

telephone number

+44 (0)1502 562244

email address

data.manager@cefas.co.uk

responsible party role

originator

Responsible party

contact position

Data Manager

organisation name

Centre for Environment, Fisheries & Aquaculture Science

full postal address

Cefas Lowestoft Laboratory

Pakefield Road

Lowestoft

NR33 0HT

UK

telephone number

+44 (0)1502 562244

email address

data.manager@cefas.co.uk

responsible party role

custodian

Metadata on metadata

Metadata point of contact

contact position

Data Manager

organisation name

Centre for Environment, Fisheries & Aquaculture Science

full postal address

Cefas Lowestoft Laboratory

Pakefield Road

Lowestoft

NR33 0HT

UK

telephone number

+44 (0)1502 562244

email address

data.manager@cefas.co.uk

responsible party role

pointOfContact

Metadata date

2017-02-14T10:27:26

Metadata language

eng