ArctoNorwegian cod Background information and possible implications of changes in spawning stock age

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WGCCC Workshop St Johns Newfoundland 9-12/5 2006
Arcto-Norwegian cod Background information and
possible implications of changes in spawning
stock age structure (1913-2004)
Geir Ottersen
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Arcto-norwegian cod Seasonal migrations and
spawning grounds
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WHY WORRY ABOUT JUVENATION?

• Older, larger, more experienced N. Atlantic cod
  have a disproportionally higher reproductive
  capacity becausea) Larger females produce
  relatively more eggs (Marteinsdottir
  Thorarinsson 1998).b) Older fish spawn over a
  more prolonged period and eggs are
  distributed over a broader vertical and
  horisontal range thus having increased
  probability of a sufficient number surviving c)
  Size of cod eggs and larvae increase with
  maternal size (Chambers and Waiwood 1996
  Vallin and Niesling 2000).d) Larger eggs size
  leads to higher survival both as eggs
  (Solemdal et al 1995) and yolk-sac larvae
  (Nissling et al. 1998).e) Larger, faster growing
  larvae have increased survival (Field Meekan
  Fortier 1996 Theory Houde 1987).f) Older
  fish may have a key behavioral role in spawning
  migrations (Rose 1993).

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Temperature average from 0-200m and across
stations along the Kola meridian in the
south-central Barents Sea
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