One pressure too many?Diet shifts in a declining Arctic charr population   & the implications for the lake food web       ...
Outline   -Background on Windermere &stable isotope analysis of food webs   -Archived samples: diet shifts -Wider effects ...
Increase in water temperature of Windermere                 12                                                            ...
Windermere fishArctic charr (Salvelinus alpinus)Atlantic salmon (Salmo salar)Common bream (Abramis brama)             Glac...
Arctic charr – near southernmost edge of its distribution                        English Lake DistrictRoach – historically...
Windermere long-term fish research                                Arctic charr                                Fishery reco...
Long-term fish abundance                        6000                        5000Abundance (fish ha-1)                     ...
Roach increase                                  50CPUE (Fish 100 m 2 net-1 day-1)                                  40     ...
Arctic charr decrease                  6                  5CPUE (fish h-1)                  4                  3          ...
Decline in Zooplankton Abundance                            Summer zooplankton abundance 1985 - 2010                    5....
Windermere Food Web – A Stable Isotope Picture                                             Pike                           ...
Methods  Measured δ13C & δ15N of archived samples               (1985 – 2010):   - zooplankton (predatory & herbivorous)  ...
Proportions of Prey in Charr Diet                             Calculated from δ13C & δ15N                      1          ...
Proportions of Prey in Roach Diet                             Calculated from δ13C & δ15N                      1          ...
Proportions of Prey in Perch Diet                             Calculated from δ13C & δ15N            Predatory            ...
Proportions of Prey - Calculated from δ13C & δ15NProportion in Diet                      1                     0.8        ...
Proportions of Prey in Pike Diet                        Calculated from δ13C & δ15N                      1                ...
Conclusions• Diet of charr included more deep water & less near shore food  sources after roach expansion• Roach feed on n...
Acknowledgements• CEH Lake Ecosystem Group - especially: Ian Winfield, Steve  Thackeray, Stephen Maberly, Ian Jones, Mitzi...
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One pressure too many?

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Smyntek et al 2011 presentation at the Symposium for European Freshwater Sciences

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One pressure too many?

  1. 1. One pressure too many?Diet shifts in a declining Arctic charr population & the implications for the lake food web Peter Smyntek & Jonathan Grey School of Biological and Chemical Sciences Queen Mary University of London
  2. 2. Outline -Background on Windermere &stable isotope analysis of food webs -Archived samples: diet shifts -Wider effects on the ecosystem
  3. 3. Increase in water temperature of Windermere 12 10.7 °C 11Temperature oC 9.8 °C 10 9 8 1940 1950 1960 1970 1980 1990 2000 2010 Year
  4. 4. Windermere fishArctic charr (Salvelinus alpinus)Atlantic salmon (Salmo salar)Common bream (Abramis brama) Glacial relic speciesBrown trout (Salmo trutta)Bullhead (Cottus gobio)European eel (Anguilla anguilla)European perch (Perca fluviatilis)Minnow (Phoxinus phoxinus)Northern pike (Esox lucius)River lamprey (Lampetra fluviatilis)Roach (Rutilus rutilus)Rudd (Scardinius erythrophthalmus) Invasive speciesSea lamprey (Petromyzon marinus)Stone loach (Barbatula barbatula)Tench (Tinca tinca)Three-spined stickleback (Gasterosteus aculeatus)
  5. 5. Arctic charr – near southernmost edge of its distribution English Lake DistrictRoach – historically a southern distribution but expanding northwards
  6. 6. Windermere long-term fish research Arctic charr Fishery records 1966+Northern pike Arctic charrGill nets Gill nets1944+ 1940+Perch RoachTraps Gill nets1943+ 1995+ Hydroacoustics 1990+
  7. 7. Long-term fish abundance 6000 5000Abundance (fish ha-1) 4000 Start of roach expansion 3000 2000 1000 0 1990 1995 2000 2005 2010 Year • Increase since late 1990s, particularly in south basin
  8. 8. Roach increase 50CPUE (Fish 100 m 2 net-1 day-1) 40 30 20 10 0 1995 2000 2005 2010 Year
  9. 9. Arctic charr decrease 6 5CPUE (fish h-1) 4 3 2 1 0 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year • Since early 2000s, particularly in south basin; 2010 values are the lowest on record
  10. 10. Decline in Zooplankton Abundance Summer zooplankton abundance 1985 - 2010 5.0 4.5Numbers per liter 4.0 3.5 3.0/L 3.0 2.5 2.0/L 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 Decrease in summer zooplankton by 33% following roach expansion (1985-1995 vs. 1996 – 2010)
  11. 11. Windermere Food Web – A Stable Isotope Picture Pike Perch Arctic charrTrophic Level Indicator Roach δ15N Macroinvertebrates Zooplankton Benthic Algae Phytoplankton & Detritus Near shore Offshore (Littoral) δ13C (Pelagic) Energy Source
  12. 12. Methods Measured δ13C & δ15N of archived samples (1985 – 2010): - zooplankton (predatory & herbivorous) - macroinvertebrates (nearshore/littoral) - chironomids (deep offshore/profundal) -fish scales & opercular bones (gill cover)-Dietary mixing model: proportions of potential food items consumed
  13. 13. Proportions of Prey in Charr Diet Calculated from δ13C & δ15N 1 PredatoryProportion in Diet 0.9 Cyclops zooplankton 0.8 0.7 Herbivorous 0.6 Daphnia zooplankton 0.5 0.4 0.3 Macroinverts Macroinverts 0.2 0.1 0 Chironomids Chironomids 1985-1987 1992-1994 2000-2002 2003-2005 2009-2010 Period of Years
  14. 14. Proportions of Prey in Roach Diet Calculated from δ13C & δ15N 1 Cyclops Predatory 0.9 zooplankton 0.8Proportion in Diet 0.7 Herbivorous Daphnia 0.6 zooplankton 0.5 0.4 Macroinverts 0.3 Macroinverts 0.2 0.1 Chironomids Chironomids 0 2000 2005 2009 2010 Year
  15. 15. Proportions of Prey in Perch Diet Calculated from δ13C & δ15N Predatory 1 Cyclops zooplanktonProportion in Diet 0.9 0.8 Herbivorous 0.7 Daphnia zooplankton 0.6 0.5 0.4 Macroinverts Macroinverts 0.3 0.2 0.1 Chironomids Chironomids 0 2000 2005 2009 2010 Year
  16. 16. Proportions of Prey - Calculated from δ13C & δ15NProportion in Diet 1 0.8 0.6 0.4 0.2 0 1985-1987 1992-1994 2000-2002 2003-2005 2009-2010 1 Predatory Cyclops 0.8 zooplankton 0.6 Daphnia Herbivorous zooplankton 0.4 Macroinverts Macroinverts 0.2 Chironomids Chironomids 0 1 0.8 0.6 0.4 0.2 0 2000 2005 2009 2010
  17. 17. Proportions of Prey in Pike Diet Calculated from δ13C & δ15N 1 0.9 Roach 0.8Proportion in Diet 0.7 0.6 Perch 0.5 0.4 0.3 0.2 Charr 0.1 0 2000 2005 2009 2010 Year
  18. 18. Conclusions• Diet of charr included more deep water & less near shore food sources after roach expansion• Roach feed on near shore food sources• Perch diet shifted: near shore to offshore• Pike diet shifted: offshore-based (charr) to near shore-based (roach)• Change in carbon/energy flow through the ecosystem following roach invasion
  19. 19. Acknowledgements• CEH Lake Ecosystem Group - especially: Ian Winfield, Steve Thackeray, Stephen Maberly, Ian Jones, Mitzi DeVille, Ben James, Janice Fletcher, Alex Elliott, Jack Kelly & Heidrun Feuchtmayr• QMUL: Ian Sanders, Nicola Ings and Michelle Jackson• CEH Lancaster: Helen Grant• Freshwater Biological Association & Queen’s University Belfast• Natural Environment Research Council (NERC)

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