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Why mackerel must be taken very SERIOUS!
Jens Christian Holst Scientific advisor Ecosystembased jens@ecosystembased.com
Why mackerel must be taken very SERIOUS! Jens Christian Holst - - PowerPoint PPT Presentation
Why mackerel must be taken very SERIOUS! Jens Christian Holst - - PowerPoint PPT Presentation
Why mackerel must be taken very SERIOUS! Jens Christian Holst Scientific advisor Ecosystembased jens@ecosystembased.com Living together = competition and predation Salmon postsmolt migrations first three months at sea 6000+ scientific
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Living together = competition and predation
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Salmon postsmolt migrations first three months at sea
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6000+ scientific catches
- f postsmolt
starting 1991
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Postsmolt salmon migration first three months at sea
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Collapse in postsmolt growth
Salsea-Merge 2011
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Reduced postsmolt feeding
Salsea- Merge 2011
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Extreme increase in mackerel stock distribution and stock size
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Nøttestad 2011
Mackerel distribution 2004 and 2009
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Mackerel distribution 2019
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2007 2010 2011 2012 2013 2014 2015 2016
Nøttestad og Utne, Institute of Marine Research, Norway, in Naturen 2016
July-august trawl survey
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2007 2016
Three times larger geographic distribution, double density: sixfold increase
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Olavsdottir et al. 2015
Mackerel growth:Total collapse
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Extreme increase in overlap between mackerel and salmon smolts
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Mackerel eggs May1992 Mackerel eggs May 2016
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Highest mackerel egg densities in 2016
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Mackerel also spawning all way up to Northern Norway after 2008
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Mackerel fisheries April-June
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Mackerel fisheries July -August
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Postsmolt life catching aquarium!
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Cannibalism in mackerel and the potential for postsmolt predation
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30 cm mackerel
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30 cm mackerel
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30 cm mackerel 12.5 cm smolt
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Cannibalism is today common in the starving mackerel
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We know exactly where the postsmolts and the mackerel overlap
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Camera Camera Anticipated picture from underwater camera Steel-bar Triangle of Steel-bars Trawler
Video trawling
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VIDEO FRAME
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A B C D
60° 58° 10° 5°
RV SCOTIA MAY 2005
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Continuous smolt distribution along trawling track
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