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Hannes Höffle, Ph.D. student DTU Aqua Section Oceanography Supervisors: Peter Munk, DTU Aqua

Spatial patterns in the distribution and early life characteristics of North Sea cod under the influence of climate change. Hannes Höffle, Ph.D. student DTU Aqua Section Oceanography Supervisors: Peter Munk, DTU Aqua Brian MacKenzie, DTU Aqua.

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Hannes Höffle, Ph.D. student DTU Aqua Section Oceanography Supervisors: Peter Munk, DTU Aqua

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  1. Spatial patterns in the distribution and early life characteristics of North Sea cod under the influence of climate change Hannes Höffle, Ph.D. student DTU Aqua Section Oceanography Supervisors: Peter Munk, DTU Aqua Brian MacKenzie, DTU Aqua Climate impacts on the Baltic Sea, Bornholm 09

  2. Table of contents • Background: The cod stock in the North Sea and the early life • Results of IBTS cruises 2004 and 2009 (preliminary) • Comparison of the two years and outlook to future work Climate impacts on the Baltic Sea, Bornholm 09

  3. The cod stock in the North Sea – How much is left? • The Spawning Stock Bioass (SSB) is estimated to be around 50,000 t. ICES 2006 Climate impacts on the Baltic Sea, Bornholm 09

  4. The early life – a critical stage Predation Physiological stress Disease Problems in Development Pollution Starvation Fuiman & Werner 2002 Recruitment Climate impacts on the Baltic Sea, Bornholm 09

  5. What does a cod larvae need and how might climate influence that? Supply from Atlantic Transport weakened since mid 80’s More and stronger extreme weather events Food: i.e. Calanus finmarchicus Balance of Turbulence and Stratification Suitable Temperature Suitable Oxygen Suitable Salinity Higher inflow and precipitation may change position of front Faster metabolism More active (and more?) predators Less soluble Climate impacts on the Baltic Sea, Bornholm 09

  6. How to assess the cod stock in the future?- The SUNFISH project Approach: Cod (Gadus morhua) Sandeel (Ammodytes sp.) SUNFISH = Sustainable Fisheries, Climate Change and the North Sea ecosystem Problem: Extrapolating from historical observations may be unreliable in the future Objectives: • Understand and evaluate climate change effects • Quantify effects on fishes Drift & Dispersal during early life Predictive models Including environmental cues Climate impacts on the Baltic Sea, Bornholm 09

  7. Cod eggs, larvae and pelagic juveniles – my part of the story 3. Prey preference & Settlement Do they run out of pelagic food? 2. Determinantes for drift and dispersal? 1. Distribution of eggs & early larvae Fixed behaviour or hydrography? Climate impacts on the Baltic Sea, Bornholm 09

  8. Investigation of early life stages – IBTS 1Q 2004 • Hypothesis: Spawning areas are linked to recurrent hydrographic features like Salinity fronts. • Indicators for spawning areas: -) Mature females in trawls -) eggs & larvae in plankton samples • Findings:High Gadoid egg abundances: -) at Dogger bank -) at Fisher Banks -) off Norwegian coastal current -) off northern Scotland High plaice egg abundances: -) at Fisher Banks -) off Norwegian coastal current • Early stage larvae were abundant where eggs occurred in high concentrations. • Peak egg and larvae abundances corresponded to (frontal) hydrography. • Salinity fronts may change due to climate change, because of shifts in FW-inflow. Climate impacts on the Baltic Sea, Bornholm 09

  9. Investigation of early life stages – IBTS 1Q 2004 Depth Salinity Climate impacts on the Baltic Sea, Bornholm 09

  10. IBTS – cruise 1Q 200931st January – 17th February 2009 • Sampling of cod ovaries during the day shift • In total 68 plankton samples taken • Sampling between 18:00 hours and 07:00 hours • Sampling gear: Bongo Net with CTD and Depth Sounder • Preservation of samples in Ethanol (500 µm) and Formaldehyde (330 µm) • Sorting of single egg samples onboard (sample in Seawater on ice) Climate impacts on the Baltic Sea, Bornholm 09

  11. Ditstribution of Eggs in the North Sea Total eggs counted: 9462 Calculated number of eggs in Samples: 51,445 Depth Climate impacts on the Baltic Sea, Bornholm 09

  12. Distribution of Eggs in the North Sea Depth Climate impacts on the Baltic Sea, Bornholm 09

  13. Size range of Eggs sampled in 2009 Climate impacts on the Baltic Sea, Bornholm 09

  14. How does 2009 compare to 2004?Gadoids Gadoids 2004 Gadoids 2009 Salinity Climate impacts on the Baltic Sea, Bornholm 09

  15. What determines the major distributional patterns of cod eggs and early larvae? • 2009 data is preliminary, changes may occur • Difference in absolute number may be due to different timing of surveys. • Reduced number of Gadoids south of Dogger Bank. Shift of Salinity front? Climate impacts on the Baltic Sea, Bornholm 09

  16. Outlook to future work • Next cruise: IBTS 3Q 2009, 11th to 28th of August 2009 • Target: Pelagic juvenile Cod (and other Gadoids) • New questions: • Does cod prefer to spawn along certain salinity isolines? • Will there be new predators on larval and juvenile cod? • How will more events of extreme weather influence the survival? Climate impacts on the Baltic Sea, Bornholm 09

  17. Acknowledgements • Peter Munk for a crash course in Surfer 7. • Erik Selander for microscope photos. • Zeren Gürkan and Niels Jørgen Pihl for help during the field sampling. Climate impacts on the Baltic Sea, Bornholm 09

  18. Thank you for your attention!

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