1. Effects of underwater habitat quality on the top predator Baltic cod and its food web interactions
and Baltic fisheries!
Barbara Bauer, V. Bartolino, M. Casini, A. Hoff, H. E. M. Meier, P. Margoński, B. Müller-Karulis, A. Orio, M. Rahikainen, S. Saraiva, J. Warzocha, J. Kownacka, J. Steenbeek and M. T. Tomczak

2. Ongoing efforts for nutrient load reductions to reduce eutrophication

3. Indirect consequences?

4. dynamic spatial food web model: Ecospace
Methods
3 nutrient load scenarios
regional ocean model:
RCO-SCOBI
dynamic spatial food web model: Ecospace -
Agricultural expansion
BSAP
REF
time-series of maps
O2, salinity, temperature...
climate change
A1B (IPCC)
Scenarios run ,
results: avg

5. increasing nutrient loads
Results: drivers
BSAP
REF
AgrExp
Bottom O2 concentration (ml/l)
Cod Reproductive Volume (km3)
Phytoplankton biomass in the water column (t/km2)
increasing nutrient loads

6. Results: fish distributions
max.value of stock
BSAP
REF
AgrExp
Cod
benefit from higher O2 concentrations under low nutrient loads
Flounder
- benefits from increased productivity under high nutrient loads.
- negatively related to cod
Sprat
Herring
distribution least affected by nutrient loads:
complex interactions among various factors
increasing nutrient loads

7. Results: fish distributions
max.value of stock
BSAP
REF
AgrExp
Cod
benefit from higher O2 concentrations under low nutrient loads
Flounder
- benefits from increased productivity under high nutrient loads.
- negatively related to cod
Sprat
Herring
distribution least affected by nutrient loads:
complex interactions among various factors
increasing nutrient loads

8. Results: fishing efforts
increasing nutrient loads
Results: fishing efforts
mid-size (24-40 m) demersal trawlers
BSAP
REF
AgrExp
small (<12 m) passive gears
Relative effort
(compared to avg. 2004)
mid-size pelagic trawlers
widely spread fishing effort:
many similarly profitable fishing grounds
small areas of intense fishing

9. Conclusion
Nutrient load management has substantial consequences for future locations of fishing grounds.
The scenario assuming the lowest nutrient loads substantially increased the area suitable for cod -> potential fishing grounds
physical oceanography
bio-geochemistry
spatial and trophic ecology
bioeconomics

10. Thank you!