North Sea Case Study by dfhdhdhdhjr


									North Sea Case Study

UNCOVER Report Writing Workshop
       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
 Cod        Reduced        Increased risk     Overfished      Above target

Plaice        Full          Harvested         Overfished      Below target
          reproductive      sustainably

Herring   Increased risk     Harvest         Appropriate      Above target
             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
        Management - Cod
• Former recovery plan (2004) was not
  precautionary – cut in quota not matched
  by cut in effort.
• Another recovery plan (2009) was
• Is precautionary if implemented and
• Effort management introduced (2009) –
  gear and metier dependent.
      Lessons learned - Cod
• Despite measures cod has not recovered
• Low F, but Recruitment has been recently
• 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
• 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
• SSB is estimated to have increased above the
• 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
     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
• 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
        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
• ICES assumes that the recruitment will remain at the low
     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
 Impact of precautionary plans
Stock     Previous    Precautionary   What
           status         plan?     happened?
 Cod      Collapsed       Yes         Not
Plaice    Collapsed        ?       Recovered

Herring    Healthy        Yes       Danger of
                   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
•   Results Based Management
•   Top down vs Local management

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