1 PELGAS : PELGAS : acoustic acoustic survey on the survey on - - PDF document

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1 PELGAS : PELGAS : acoustic acoustic survey on the survey on - - PDF document

Feb 24, 2023 575 likes •638 views

French information on blue whiting : PELGAS : acoustic survey on the From Pelgas survey shelf From Evhoe survey 2000 From the fishery (self sampling) From discard sampling News from the Joseph Roty survey 1 2 PELGAS : PELGAS :

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French information on blue whiting : From Pelgas survey From Evhoe survey From the fishery (self sampling) From discard sampling News from the Joseph Roty survey

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PELGAS : acoustic survey on the shelf 2000

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PELGAS : acoustic survey on the shelf 2002

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PELGAS : acoustic survey on the shelf 2003

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PELGAS : acoustic survey on the shelf 2004

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PELGAS : acoustic survey on the shelf 2005

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PELGAS : acoustic survey on the shelf 2006

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PELGAS : acoustic survey on the shelf 2007

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PELGAS : acoustic survey on the shelf 2008

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PELGAS : acoustic survey on the shelf 2009

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PELGAS : acoustic survey on the shelf 2010

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EVHOE: groundfish survey (bottom trawl) (Bay of Biscay + Celtic Sea) since 1997

1998 2000 2002 2004 2006 2008 2010 0.0e+00 5.0e+09 1.0e+10 1.5e+10 2.0e+10

Blue whiting in Bay of Biscay & Celtic Sea Evhoe survey

Year Abundance index (+ SD)

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13 1990 1995 2000 2005 2010 0e+00 2e+09 4e+09 6e+09 8e+09 Blue whiting in Bay of Biscay Evhoe survey Year Abundance index (+ SD)

EVHOE: groundfish survey (bottom trawl) (Bay of Biscay + Celtic Sea) since 1997

14 1998 2000 2002 2004 2006 2008 2010 0.0e+00 5.0e+09 1.0e+10 1.5e+10 2.0e+10 Blue whiting <=20 cm in Bay of Biscay & Celtic Sea Evhoe survey Year Abundance index (+SD)

EVHOE: groundfish survey (bottom trawl) (Bay of Biscay + Celtic Sea) since 1997

15 1990 1995 2000 2005 2010 0e+00 2e+09 4e+09 6e+09 8e+09 Blue whiting <=20 cm in Bay of Biscay Evhoe survey Year Abundance index (+SD)

EVHOE: groundfish survey (bottom trawl) (Bay of Biscay + Celtic Sea) since 1997

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EVHOE:

1997 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 1998 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 1999 0.00 200.00 400.00 600.00 800.00 1000.00 1200.00 10 20 30 40 50 60 70 80 90 100 110 2000 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2001 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2002 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2003 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2004 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2005 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2006 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2007 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2008 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 2009 200 400 600 800 1000 1200 1400 10 20 30 40 50 60 70 80 90 100 110 2010 200 400 600 800 1000 1200 10 20 30 40 50 60 70 80 90 100 110 17

Self-sampling 2007

09/10/07-11/11/07 14/11/07-06/12/07 07/10/08-03/11/08 08/11/08-25/11/08 28/09/09-3/11/09 08/04/08-26/05/08 21/03/09-19/04/09 23/04/09-11/05/09 08/01/08-22/02/08 28/02/08-23/03/08 07/01/09-09/02/09 13/02/09-14/03/09 05/01/10-07/02/10 11/02/10-10/03/10 16/03/10-17/04/10 18

Self-sampling: since 2007

Merlan bleu - Autoéchantillonnage

0% 5% 10% 15% 20% 25% 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 taille (cm) fréquence 2007-S 2008-S 2009-S 2008-N 2009-N 2010-N

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French catches: bigger sizes

Merlan bleu - 2009

. 5. 10. 15. 20. 25. 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 longueur (cm) fréquence (%) IS FO ES NOR-MIF NOR RU PT FR-Nord FR-Sud NL 20

Some more information

Blue whiting - ByCatch (discards) from the Nephrops fishery in the Bay of Biscay

100 200 300 400 500 600 700 800 900 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 length (cm) 2007-3 2009-2 2009-3 2009-4 2010-1 2010-2 2010-3

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Collaborative study between French fishing company and Ifremer in 2011

Objectives of study Investigate evidence for stock structure of blue whiting by analysing spatial structure of individual condition analysing spatial structure of spawning fish with different nursery areas during juvenile phase North South

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Sampling plan in 2011

Part 1) Normal fishing operation 17/1 – 11/2 and 26/2 – 16/3 between 52°North (Porcupine) and St-Kilda 57° 40 North Part 2) Survey type sampling 17/3 – 31/3 Scotland Faroese

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Data collection

Pelagic trawling

  • temperature on trawl
  • mean depth of trawling
  • mean depth of sea floor
  • duration of trawl haul
  • total catch (kg)

For 30 individuals per haul (randomly selected):

  • individual weight & length (lower 0.5 cm)
  • sex and maturity stage
  • otoliths (10 individuals randomly selected

Measurements during transects

  • registration of acoustic echosounder signal (38 kHz, ER60)

Laboratory analyses

  • age from otoliths
  • otolith growth increments for juvenile phase
24 15 20 25 30 35 40 45 50 50 100 150 200 250 Length Frequency 17/1 - 11/2/2011 26/2 - 16/3/2011 17/3 - 31/3/2011

First results: Cumulated length distribution

Commercial Survey
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First results: Acoustic school detection

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First results: Length-weight relationship

Scale not compensated for roll and pitch!

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Next steps

  • Contacts have been established to complement data

with samples collected on scientific blue whiting survey

  • Age reading and growth increments for collected
  • tolithes
  • Analysis of acoustic data to provide insight into spatial

distribution of shoals

  • Statistical spatial analysis of weight-at-age and

statistical spatial analysis of otolith growth increments in terms of evidence for stock structure