North Sea Case Study by dfhdhdhdhjr

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									North Sea Case Study

UNCOVER Report Writing Workshop
           Holte
       February 2010
                   Status Quo
Stock         SSB in       F in relation to F in relation to F in relation to
            relation to    precautionary high long-term agreed target
          precautionary         limits            yield
               limits
 Cod        Reduced        Increased risk     Overfished      Above target
          reproductive
            capacity

Plaice        Full          Harvested         Overfished      Below target
          reproductive      sustainably
            capacity

Herring   Increased risk     Harvest         Appropriate      Above target
                            sustainably
             Status Quo - Cod
• “…ICES classifies the stock as suffering reduced
  reproductive capacity and as being at risk of being
  harvested unsustainably.
• SSB has increased since its historical low in 2006, but
  remains below Blim.
• Fishing mortality declined after 2000, but in 2008
  increased, predominantly as a consequence of
  increased discarding and is currently estimated to be
  between Flim and Fpa.
• The 2005 year class is estimated to be one of the most
  abundant amongst the recent below-average year
  classes. The 2008 year class is estimated to be one of
  the lowest in the series.”
Status Quo - Cod
           Status Quo - Cod
• SSB declined since late 90s.
• Recent small increase as 2005 year class
  matures combined with relatively low F.
• Recruitment – 1996 last large year class. 2005
  relatively high. But 2006 and 2007 weak. 2008
  expected to be weak
• F has decreased but recent values are
  uncertain. F increased recently due to increase
  in discarding.
• Discard mortality > human consumption
  mortality
        Management - Cod
• Former recovery plan (2004) was not
  precautionary – cut in quota not matched
  by cut in effort.
• Another recovery plan (2009) was
  evaluated
• Is precautionary if implemented and
  enforced.
• Effort management introduced (2009) –
  gear and metier dependent.
      Lessons learned - Cod
• Despite measures cod has not recovered
• Low F, but Recruitment has been recently
  poor
• Stock structure and diversity (RASER)
• High F on low ages prevents growth, even
  if recruitment is high.
          Lessons learned - Cod
• Mixed fishery – current plan is single species
• Evaluation of plan was single species (e.g. no cannibalism) – may
  overestimate probability of recovery
• Multispecies modelling (SMS) demonstrate predation is key
  biological process
• Multispecies modelling increases uncertainty – SMS vs EwE
• Mixed-species nature of fishery and international dimension are two
  main factors contributing to decline (Bannister, 2004).
• WKMIXFISH 2009 – evaluated consistency of single stock plans.
  Cod fared badly – over quota catches. Effort restrictions should
  help.
• SMS model – mesh size changes. Increases led to higher
  probability of recovery.
       Lessons learned - Cod
• Specify ‘recovery’ – HCRs in 2008 evaluations
  had no agreed criteria
• Substocks important?
• Impact of environmental change? Warming lead
  to reduction in recruitment (STECF 2007).
• Stock shifted northward and deeper? – highly
  speculative and often contradictory
• Should reference points (MSY) be multispecies?
          Status Quo - Plaice
• ICES classifies the stock as having full
  reproductive capacity and as being harvested
  sustainably.
• SSB is estimated to have increased above the
  Bpa.
• Fishing mortality is estimated to have decreased
  to below Fpa and Ftarget.
• Recruitment has been of average strength from
  2005 onwards. The recruitment in 2008 is just
  below the long-term average.”
Status Quo - Plaice
         Status Quo - Plaice
• STECF advised a recovery plan (2003)
• ICES proposal for a multi-annual plan
  tabled (2005)
• No agreed EU – Norway plan
• EU agreed long-term management plan
  (2007). Uses TAC and effort restrictions.
• Evaluated in 2008.
• Not yet been concluded if plan was
  precautionary
     Lessons learned - Plaice
• Plaice – recovered - why?
• Reduction in F – driven by?
  – Management plan
  – Reduction in fleet capacity
  – Fuel prices drive down effort
• STECF 2009 – too soon to attribute
• Suggests inclusion of socio-economics in
  evaluation of proposed plans is essential
       Lessons learned - Plaice
• Stock age diversity did not impact on recruitment
• Allowed stock to take advantage of low F – compared to
  Cod
• Low F laid foundation of recovery, still needed high Rec.
  i.e. low F does not guarantee recovery.
• Cooler water may reduce future recruitment ?
• Inclusion of biological information (e.g. TEP) may lead to
  alternative perception of stock status and ref pts?
• Question is now – how to prevent future collapse –
  precautionary plan. Recommended to use MSE.
        Status Quo - Herring
• “…ICES classifies the stock as being at risk of
  having reduced reproductive capacity and
  harvested sustainably.
• The SSB in autumn 2008 was estimated at 1.0
  million t, and is expected to remain below Bpa
  (1.3 million t) in 2009.
• F2-6 in 2008 was estimated at 0.24, above the
  management target F2-6 (for this state of the
  stock = 0.14).
• The year classes since 2002 are estimated to be
  among the weakest since the late 1970s.”
Status Quo
  Herring
        Status Quo - Herring
• Spawning stock biomass has fluctuated:
  – ~ 4.5 million tonnes in the late 1940s
  – less than 100 000 tonnes in the late 1970s
• Demonstrated robustness in relation to
  recovery from low levels once fishing
  mortality is curtailed in spite of recruit-
  ment levels being adversely affected.
          Status Quo - Herring
• Management plan 1996 – reviewed and adapted every
  few years.
• Precautionary ref pts adopted in 1998.
• Previous plan was precautionary.
• Critical issues is risk of SSB falling below Blim
• EU-Norway adjust plan to account for poor recruitment
  (2008) – quotas to reduce F.
• New plan also precautionary
• Even though the current and previous management
  plans were considered “precautionary”, the stock
  declined below biomass targets in the mid-2000s.
• This was primarily caused by a change in productivity of
  the stock
• Exacerbated by the failure of the managers and industry
  to adhere to the existing management plan
           Status Quo - Herring
• The harvest control rule was revised again in 2009
• Reduction of the effective target fishing mortality through
  a change in trigger biomass.
• SSB is expected to increase in 2010 & 2011
• Indicates current management can reverse the decline
  and stabilize it above the present level.
• The 2008 year class is within the range of recent low
  recruitments
• ICES assumes that the recruitment will remain at the low
  level.
     Lessons learned - Herring
• Larval survival - each spawner now produces
  less than one recruit per year.
• Specific causes are unknown; the pattern in
  recruitment from 1970 to 2005 appears similar to
  environmental signals in the North East Atlantic
  such as the Atlantic Multidecadal Oscillation.
• Change in productivity combined with failure to
  adhere to the existing management plan
• Suggests that socio-economics and enforcement
  need to be included in plan evaluation?
     Lessons learned - Herring
• After collapse in 1970s, only three of the four
  North Sea herring stocks actually recovered, the
  fourth stock (Downs) taking substantially longer
  to recover.
• Recovered stocks might not be as productive.
• Sub-stocks – work on herring West of British
  Isles – fail to detect overexploitation -
  overestimate the probability of recovery and
  underestimate the risk of stock collapse.
    Lessons learned - Herring
• Compensation in recruitment has occurred
  in North Sea herring, and it was stronger
  after the collapse of the stock
• There is more variability in recruits per unit
  spawning stock size when the stock is
  smaller – impact of substocks
• The importance of herring in multispecies
  models has not been fully explored.
            Generic HCRs
• STECF 2008- codoid and herringoid
• Picking max of F0.1 and Fsq was less
  effective than picking F0.1.
• Inter-species comparisons not carried out.
• STECF recommended the approach be
  developed.
 Impact of precautionary plans
Stock     Previous    Precautionary   What
           status         plan?     happened?
 Cod      Collapsed       Yes         Not
                                   recovered
Plaice    Collapsed        ?       Recovered


Herring    Healthy        Yes       Danger of
                                    Collapse
                   General thoughts
•   Cannot recover without low F – some control
•   But you also need high Rec – no control
•   Plans need some target time and acceptable level of risk to be defined
•   Attributing recovery to plan – time taken
•   Is recovered stock ‘the same’?
•   Socio-economics needs to be included in evaluations
•   Fish stocks can be threatened with unsustainability even if not exploited
•   Is interaction between env and exploitation too complicated to model?
•   How precautionary is precautionary?
•   Further development of MSE approach is recommended by ICES and
    STECF
•   Results Based Management
•   Top down vs Local management

								
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