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Spatial patterns in the distribution and early life characteristics of North Sea cod under the
influence of climate change
Hannes Höffle, Ph.D. studentDTU AquaSection Oceanography
Supervisors: Peter Munk, DTU AquaBrian MacKenzie, DTU Aqua
Climate impacts on the Baltic Sea, Bornholm 09
17/04/2008Presentation name2 DTU Aqua, Technical University of Denmark
Table of contents
1. Background: The cod stock in the North Sea and the early life
2. Results of IBTS cruises 2004 and 2009 (preliminary)
3. Comparison of the two years and outlook to future work
Climate impacts on the Baltic Sea, Bornholm 09
17/04/2008Presentation name3 DTU Aqua, Technical University of Denmark
The cod stock in the North Sea – How much is left?
• The Spawning Stock Bioass (SSB) is estimated to be around 50,000 t.
Climate impacts on the Baltic Sea, Bornholm 09
ICES 2006
17/04/2008Presentation name4 DTU Aqua, Technical University of Denmark
The early life – a critical stage
Predation
Physiological stress
Disease
Problems in Development
Pollution
Starvation
RecruitmentClimate impacts on the Baltic Sea, Bornholm 09
Fuiman & Werner 2002
17/04/2008Presentation name5 DTU Aqua, Technical University of Denmark
What does a cod larvae need and how might climate influence that?
Food: i.e. Calanus finmarchicus
Suitable SalinitySuitable OxygenSuitable Temperature
Faster metabolism
More active (and more?) predators
Balance of Turbulence and Stratification
Supply from Atlantic
Transport weakened since mid 80’s
More and stronger extreme weather events
Higher inflow and precipitation may change position of front
Less soluble Climate impacts on the Baltic Sea, Bornholm 09
17/04/2008Presentation name6 DTU Aqua, Technical University of Denmark
How to assess the cod stock in the future?- The SUNFISH project
SUNFISH = Sustainable Fisheries, Climate Change and the North Sea ecosystem
Problem:Extrapolating from historical observations may be unreliable in the future
Objectives:1.Understand and evaluate climate change effects
2.Quantify effects on fishes
Climate impacts on the Baltic Sea, Bornholm 09
Approach: Cod (Gadus morhua)
Sandeel (Ammodytes sp.)
Drift & Dispersal
during early life
Predictive models
Including environmental cues
17/04/2008Presentation name7 DTU Aqua, Technical University of Denmark
Cod eggs, larvae and pelagic juveniles – my part of the story
Climate impacts on the Baltic Sea, Bornholm 09
1. Distribution of eggs & early larvae
Fixed behaviour or hydrography?
2. Determinantes for drift and dispersal?
3. Prey preference & Settlement
Do they run out of pelagic food?
17/04/2008Presentation name8 DTU Aqua, Technical University of Denmark
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
17/04/2008Presentation name9 DTU Aqua, Technical University of Denmark
Investigation of early life stages – IBTS 1Q 2004
Climate impacts on the Baltic Sea, Bornholm 09
DepthSalinity
17/04/2008Presentation name10 DTU Aqua, Technical University of Denmark
•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)
IBTS – cruise 1Q 200931st January – 17th February 2009
581012
20
22
2426283032
41
4951535559
61 6371
73
7577
79
81
89919397
99 101
110112 114 116
118126
128
130
132
134136
138
149
152156
165173
176179
190193
196200
215217219221
223225
-3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12
Longitude
D anish Bongo sam pling IBTS 2009
50
51
52
53
54
55
56
57
58
59
60
61
La
titud
e
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
E6 E7 E8 E9 F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 G 0 G 1 G 2
Climate impacts on the Baltic Sea, Bornholm 09
17/04/2008Presentation name11 DTU Aqua, Technical University of Denmark
Ditstribution of Eggs in the North Sea
DepthClimate impacts on the Baltic Sea, Bornholm 09
Total eggs counted: 9462
Calculated number of eggs in Samples: 51,445
17/04/2008Presentation name12 DTU Aqua, Technical University of Denmark
Distribution of Eggs in the North Sea
Climate impacts on the Baltic Sea, Bornholm 09
Depth
17/04/2008Presentation name13 DTU Aqua, Technical University of Denmark
Size range of Eggs sampled in 2009
Climate impacts on the Baltic Sea, Bornholm 09
17/04/2008Presentation name14 DTU Aqua, Technical University of Denmark
How does 2009 compare to 2004?Gadoids
Gadoids 2004Gadoids 2009
Climate impacts on the Baltic Sea, Bornholm 09
Salinity
17/04/2008Presentation name15 DTU Aqua, Technical University of Denmark
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
17/04/2008Presentation name16 DTU Aqua, Technical University of Denmark
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
17/04/2008Presentation name17 DTU Aqua, Technical University of Denmark
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