Falling productivity as a constraint on native fish abundance. ACEAS Grand 2014 presentation. Jian Yen

1. Falling productivity as a constraint
on native fish abundance
Where have all the fish gone?
Nick Bond, Daryl Nielsen, Jim Thomson, Paul Humphries, David Crook, Jian Yen,
Gavin Butler, John Koehn, David Hohnberg, Rick Stoffels, Kirk WineMiller, Paul
Reich, Nicole McCasker, Mark Kennard, John Morrongiello

2. Historical declines

3. Historical declines
Overfishing
De-snagging
Clearing
River regulation
Invasive species

4. Historical declines
Overfishing
De-snagging
Clearing
River regulation
Invasive species

5. A bio-energetic approach

6. A bio-energetic approach
What is the current carrying capacity for fish?

7. What limits fish abundances?
a) Less primary productivity
b) Altered energy pathways
c) Non-energetic cause
d) A combination of these...
We consider (a) and (b) explicitly
What is their importance relative to (c)?

8. Approach

9. Approach
Production

10. Approach
Production
Food web

11. Approach
Production
Food web
Biomass

12. Approach
Production
Abundance
Food web
Biomass

13. Approach
Production
Food web
Biomass
Abundance
Historical Contemporary

14. Approach
Production
Food web
Biomass
Abundance
Historical Contemporary

15. Approach
Production
Food web
Biomass
Abundance
Historical Contemporary

16. Contemporary food web
DOC POM
Non-planktonic
algae
Phytoplankton Macrophytes
Non-planktonic
bacteria
Fungi
Mussels
Decapod
crustaceans
Small fish Carp
Large-bodied
native fish
Planktonic bacteria
Pelagic micro-inverts
Benthic micro-inverts
Other macro-inverts
4
3
2
1

17. Production

18. Production
Autochthonous (algae)
~21 kg C / river km . Year

19. Production
Autochthonous (algae)
~21 kg C / river km . Year
Floodplain production
~30-100 kg C / river km . Day

20. Production
Autochthonous (algae)
~21 kg C / river km . Year
Floodplain production
~30-100 kg C / river km . Day
Potentially big losses from altered flood regimes

21. Production
Autochthonous (algae)
~21 kg C / river km . Year
Floodplain production
~30-100 kg C / river km . Day
Potentially big losses from altered flood regimes

22. Summary

23. Summary
Energy availability might explain fish declines

24. Summary
Energy availability might explain fish declines
Simple food web approach can quantify this

25. Summary
Energy availability might explain fish declines
Simple food web approach can quantify this
Synthesis of historical and contemporary data

26. Summary
Energy availability might explain fish declines
Simple food web approach can quantify this
Synthesis of historical and contemporary data
New perspective on restoration/recovery