Environmental effects on fish populations: Some principles, some examples, and comparisons between large ecosystems from the Mediterranean to the Barents Sea

1. Geir Ottersen,
Institute of Marine Research, Oslo, Norway
and Centre for Ecological and Evolutionary Synthesis (CEES)
University of Oslo, Norway
Manuel Hidalgo,  Spanish Institute of Oceanography (IEO),
Balearic Oceanographic Centre, Palma de Mallorca, Spain
Valerio Bartolino, Swedish University of Agricultural Sciences,
Dept. of Aquatic Resources, Lysekil, Sweden
Juan-Carlos Molinero, Helmholtz Centre for Ocean Research,
Geomar, Kiel, Germany
Tristan Rouyer, Laboratoire Ressources Halieutiques de Sète,
Ifremer, France
Environmental effects on fish populations: Some principles, some examples, and
comparisons between large ecosystems from the Mediterranean to the Barents Sea
The wrapping up of the IDEADOS project: Workshop on Environment, Ecosystems and
Demersal Resources, and Fisheries, Palma de Mallorca from 14 to 16 November 2012

2. • Some general principles
• Climate effects on regional environment
• Environmental effects on early life stages and recruitment
• Environmental impacts on fish distribution
• Combined effects of fishing and climate
• Some comparisons
Overview

3. Some general principles

4. Through physiology,
(metabolic and reproductive processes)
Direct
response
to climate
Through biotic environment
(predators, prey, species interactions, and disease)
and abiotic environment
(habitat type and structure).
Indirect
response
to climate

5. 4 YEARS OLD COD
3,0
3,2
3,4
3,6
3,8
4,0
4,2
4,4
4,6
4,8
5,0
-1,5 -1 -0,5 0 0,5 1 1,5
Temperature anomaly (C)
Meanweigth(kg)
R2=0.67
Brander and O’Brien (2000)
Departure from mean
weight at age 4
1960 1970 1980 1990 2000
Year Class
0
-1
+1
Temperature anomaly (°C)
Departure from mean
weight at age 3
The effect of temperature on weight of North Sea cod
Direct response to climate

6. Puffin
Joel Durant, CEES
Puffin growth and food availability
Early life stages of NSS herring are positively affected by higher
temperatures, thus increasing prey availability for puffins:
Indirect
response
to climate
Age, days
0 10 20 30 40 50 60 70
Bodymass,g
0
50
100
150
200
250
300
350
400
96% (423 109
)
24% (27 109
)
51% (112 109
)
Fledgling
success
Herring larvae
abundance
The relation between the number of herring larvae (prey)
and weight and fledgling success in puffin chicks
Herring larva

7. A
B A
Climate Climate
Interactions with
other factors
B
Ecological response to climate fluctuations
Ottersen, Stenseth, Hurrell 2004, OUP

8. 10
12
14
16
18
20
22
1950 1960 1970 1980 1990 2000
Year
Ln(Recruitment)
Example: Cod at West Greenland
Recruitment
8
9
10
1950 1960 1970 1980 1990 2000
Year
SST
Temperature
9
10
11
12
13
14
15
1950 1960 1970 1980 1990 2000
Year
Ln(SSB)
Spawning Stock Biomass
M. Stein and V.A. Borovkov

9. Single climate event causes
shift in ecological state
Linear climate signal causes
shift in ecological state
when climate threshold passed.
Time
Linear ecological response
to climate signal
Climate
Ecological
Response
Ecological response to climate fluctuations

10. Climate-ecology links may change with time,
non-stationarity
Ecological response to climate fluctuations

11. NE Arctic Saithe
Year
Example: temporal pattern in recruitment dynamics
Recruitment
ln(thousandsage3)
Year
North Sea sole
Recruitment
ln(thousandsage1)

12. NE Arctic Saithe
Year
Year
North Sea sole
Recruitmentln
(thousandsage3)
Recruitmentln
(thousandsage1)
Example: temporal shift in recruitment dynamics

13. Climate effects on regional environment
Northern Annular Mode
(Arctic Oscillation)

14. Spatial variation: correlations between the NAO and SST
Stige, Ottersen.., Stenseth MEPS 2006

15. The Mediterranean Sea
Under the influence of numerous climatic processes acting at
global scales
– Northern Annular Mode (AO/NAO)
– Indian and African monsoon
– Subtropical Jets
– Atlantic depression
– Hadley Cells
Northern Annular Mode
regional scales
Complex orography
Regional winds (Mistral, Bora, …)
Mediterranean depressions
Latitudinal and longitudinal gradients
Bolle, 2003

16. A
B
C
r = 0.79; p < 0.001
Gulf of Lions
r = 0.75; p < 0.001
Ligurian Sea
r = 0.67; p < 0.001
Balearic Sea
A B C
Links between North Atlantic and regional climate 1950-2005

17. -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
0
50
100
150
200
250
300
350
400
r
frequency
r = 0.53; p < 0.01
1950 - 1977
r = 0.73; p < 0.0001
1978 - 2000
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
0
50
100
150
200
250
300
350
400
r
frequency
r = 0.27; p < 0.05
1950 - 1977
r = 0.62; p < 0.001
1978 - 2000
Links between North Atlantic and regional climate
change over time
Balearic Sea
NW Med

18. Image: Glynn Gorick for ICES
WG Cod and Climate Change
Environmental effects
on early life stages
and recruitment

19. SR relationships improvement
with environmental information
Massutí et al. 2008 J Mar Syst
IDEA index improves the SR
relationship of hake
off the Balearic Islands

20. Modelling the Spawning Stock-Recruitment
relationship for North Sea cod
North Sea cod

21. Modelling the Spawning Stock-Recruitment
relationship for North Sea cod by a linear relation?
?
?
North Sea cod

22. Modelling the Spawning Stock-Recruitment
relationship for North Sea cod by a Ricker type relation??
North Sea cod

23. Modelling the Spawning Stock-Recruitment relationship
for North Sea cod by a Beverton-Holt type relation??
North Sea cod

24. Enhancing the S-R relation by including environmental
effects in a combined Beverton-Holt and Ricker model
Apply a family of recruitment curves depending on
initial larval- and zooplankton densities
Beverton-Holt type relation at high food levels
Overcompensation (Ricker) at limited food levels:
At low food levels the time to metamorphosis is delayed to the
extent that larval mortality accumulates and makes the
recruitment curve overcompensatory
Proc. R soc. B.2011

25. Model Structure
1 log(R/S) = a + log(exp(-b•S))  log(R)-log(S)=a-bS
2 log(R/S) = a – log(1 + exp(c)•S/maxS)
3 log(R/S = a + log(exp(-b•S)•(1-Z) + 1/(1 + exp(c)•S/maxS)•Z)
4 log(R/S) = a – (a1•T) + log(exp(-b·S)•(1-Z) + 1/(1 + exp(c)•S/maxS)•Z)
1 Traditional Ricker model
2 Traditional Beverton-Holt model
3 Combined Ricker-Beverton-Holt model including a Z effect only
4 Combined Ricker-Beverton-Holt model including Z and T effects
A-priori set of stock (S) and recruitment (R) models
T is sea temperature and Z the zooplankton index developed by Beaugrand et al. (2002)
Sea temperature and Zooplankton are standardized

26. North Sea cod
Combined Ricker and Beverton-Holt, dependent
on zooplankton (based upon the data)RECRUITMENT

27. North Sea cod
Model # Parameters AIC Support*
1 2 80.4 0
2 2 80.6 0
3 3 64.6 0.24
4 4 62.3 0.76
Model selection
*normalised Akaike weights
(Burnham and Anderson 1998)
Model 4 is the most parsimoneus:
Combined Ricker-Beverton-Holt model
including zooplankton (Z) and temperature (T) effects

28. NSS herring
North Sea sole
Temperature-recruitment correlations 15-year moving windows
Barents Sea cod
Moving15-yearwindowcorrelations
[ln(R),temperature]

29. Environmental impacts on fish distribution

30. Temperature change
affects fish distribution:
Example,
cod at West Greenland
Air temperature
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990
30N
40N
50N
60N
70N
80N
90N
Latitude
Greenland
Warming Cold
Cod stock in
West Greenland
Today

31. Marked changes in distribution
of Northeast-Arctic cod with
historical temperature shift
Barents Sea
”Warm”Cold
Drinkwater 2011

32. Marked changes in spawning
distribution of capelin expected
under climate change
Barents Sea
Huse and Ellingsen 2008,
Drinkwater 2011
Present day spawning sites
Potential new spawning sites

33. Climate response from Northeast-Arctic cod
In cooling
phases:
- Spawning
sites displaced
southward
- decreasing
spawning
stock
In warming
phases:
- Spawning
sites displaced
northward
- Increasing
spawning stock
2,5
3,0
3,5
4,0
4,5
5,0
1900 1920 1940 1960 1980 2000
Year
Temperature
Sundby and Nakken (2008) IJMS

34. JUVENILE HAKE DISTRIBUTION IN THE TYRRHENIAN SEA: Horizontal
Recruits are aggregated in nurseries along the shelf-break,
not continuous, but in specific areas.
Concentration may be very high, up to >25.000 n/km2 !
Distribution of these areas (nurseries) may be explained by:
-the current pattern
-the patchy distribution of unique biocenoses (i.e., crinoids sea-bed)
Colloca et al. 2009, MEPS
Hake recruits distribution in early Autumn

35. Hake recruits and juveniles are well segregated in space.
Juveniles move on the shelf for feeding and maturing
JUVENILE HAKE DISTRIBUTION IN THE TYRRHENIAN SEA: Vertical
Bartolino et al. 2008, FishRes
White color shows high
depth preference as
function of fish length
Two distinct depth-length clusters throughout
1998-2004:
- Small hake over the slope
- Larger hake over the shelf in shallower waters

36. Combined effects of fishing and
climate

37. Balearic Sea
Combined effects fishing – climate
Increasing sensitivity of hake to climate variability
due to the accumulated fishing effect
Hake influenced by the IDEA index
after early 1980s
Hidalgo et al. 2011 MEPS

38. Balearic Sea
Combined effects fishing – climate
Increasing sensitivity to climate variability…
Fishing-climate effects synchronize CPUE variability
of many demersal species
… of the whole demersal community
Quetglas et al. in press ICES J. Mar. Sci

39. Finally, a few comparisons
between the different regions

40. Some rather obvious, but important differences
Temperature Salinity Open/closed Species richness
Barents Cold Intermediate Open Poor
Norwegian Cold Saline Open Poor
North Intermediate Intermediate Open (towards N) Intermediate
Med Temperate Saline Semi-enclosed Rich

41. Expected Climate Change Effects on European Marine Regions
Warmer waters will lead to northward movements
of species in open systems.
Examples North Sea, Norwegian Sea
In semi-enclosed seas some species may have nowhere to move.
For instance northwestern, colder parts of the Med.
Particularly in semi-enclosed seas a loss of endemic species
due to the invasion of non-indigenous species, which may adapt better
to new area with climate change.
For example Black Sea,
Southeastern Med (Red Sea invasion through Suez canal)

42. 1965
1970
1975
1980
1985
1990
1995
2000
years
0
4
8
12
D2
16
12
8
4
0
D2
1965
1970
1975
1980
1985
1990
1995
2000
years
0
4
8
12
16
16
12
8
4
0
Ligurian Sea
NAC
North Sea
NAC
North Atlantic climate triggers synchronic shifts in North and Ligurian Seas

43. Correlations between N. Atlantic climate and North Sea: r=0.80 (p<0.001)
Correlations between N. Atlantic climate and Ligurian S: r=0.79 (p<0.01)
Correlations between North and Ligurian Seas: r=0.40 (p<0.02)
Major environmental variability
patterns in the North and
Ligurian Seas are synchronous

44. Conclusions stock-recruitment
The results suggest that the stock-recruitment
relationships of both hake off the Balearic Islands
and North Sea cod are not stationary, but that they
depend on environmental conditions, respectively
the IDEA pattern or sea temperature

45. Cod Gadus morhua abundance
Barents Sea…………………………Many
Norwegian Sea……………………..Coastal only
North Sea……………………………Less than before
FINAL COMPARISON
Morey et al. 2012 MEPS
Mediterranean……………………...1, the Mallorca cod

46. Thanks for your attention!
Geir Ottersen
IMR