Ecological impacts of invasive signalcrayfish in large boreal lakes
Timo RuokonenPyhäjärvi Institute / University of Jyväskylä
Impacts on new ecosystems
• Compete with native crayfish species(Westman et al. 2002, Ecography)
• Habitat alteration by ecosystem engineering(Rodriguez et al. 2005, Freshwater Biology)
eol.org
•Change structure of macroinvertebrate
communities (Nyström et al. 1999, Oikos)
• Compete with fish for food and shelter(Guan & Wiles 1999, Conservation Biology)
• Food source of predatory fish(Nyström et al. 2006, Freshwater Biology)
Why large lakes?
• Crayfish are a newfunctional group
• Predator stocking resultsoften shifts in energydynamics (Eby et al. 2006, TREE)
• Thrive well in large lakes(Erkamo et al. 2010, Freshw. Crayfish)
• Few large scale studies ingeneral
Järvi 1910, Acta Soc. p. Faun. et Flor. fenn.
Ecological impacts of invasive signal crayfish
1. Impacts on macroinvertebrate communities
2. Impacts on littoral benthic fish3. Indirect impacts on perch parasites4. Increase in habitat connectivity?
Study lakes30
km
30 km
Littoral macroinvertebratesAre overall and snail density, diversity and community compositionnegatively affected?
-Direct predation or indirect effects?
Are impacts parallel across habitats and depths?- Influence of habitat complexity and spatial distribution?
Littoral macroinvertebrate densityStony Vegetation
Macroinvertebrate diversity
All taxa Snails
Sublittoral (4-5 m depth)
Mean density Taxa richness
δ13C & δ15N
Impacts on benthic fish
Ruokonen et al. 2012, Biological Invasions
Benthic fish densities and size
?? %?? %
Changes in food source use?
δ13C & δ15N
Changes in food source use?
Stoneloach Bullhead
Ruokonen et al. 2012, Biological Invasions
Drawing: Sven Nikander in ”Parasites of fish in Finland(In Finnish)”, Eds. E.T. Valtonen, T. Hakalahti-Sirén,A. Karvonen & K. Pulkkinen, in prep.
Impacts on parasites of perchLife cycleDiplostomum spathaceum Perch in large lakes?
Limited migration, shoals clustered indifferent parts of lakes (Bergek & Olsson2009)
Sampling
0.8-1m
2.5-3m
Nordic multimesh nets
Parasite load by host groups
Mea
nab
unda
nce 0
50
100
150 Päijänne
Saimaa
0
5
10
15012345
No crayfish Crayfish present
Pulkkinen et al. Ecosphere 2013Non-crayfish Crayfish
1) create a new link in energy transfer between the productive shallowlittoral and the less productive deep profundal?
??
2) strengthen terrestrial-aquatic linkages ?
Does signal crayfish increase habitat connectivity?
Lake Päijänne, Bay of Nyystölä
Stable isotope samplesδ13C & δ15N -ratios
Use of food sources
Feeding niche width and position inisotopic space
Use of food sources: 3-source mixing model
0
0.2
0.4
0.6
0.8
1
0-3 m 3-6 m 6-9 m > 9 m
Prop
ortio
n
Depth
Littoral
Terrestrial
Profundal
Feeding niche width and position in isotopic space
= 0-3 m
= 3-6 m
= 6-9 m
= >9 m
Capture depthLittoral andprofundal crayfish
Impacts on deeper areas?
Increase in habitat connectivity?
= 0-3 m
= 3-6 m
= 6-9 m
= >9 m
Capture depthCrayfish with littoral δ13C- signatureall over lake bottom
MORE RESEARCH!
Signal crayfish a new link in energy transferfrom littoral to profundal
Magnitude?Daily or seasonal migration?
Conclusions
• Negative impacts on native biota
• Potential to cause ecosystem level changes
• Impacts differ between groups and are habitat specific
University of Jyväskylä
Dr. Heikki Hämäläinen
Prof. Juha Karjalainen
Dr. Mikko Kiljunen
Prof. Roger Jones
MSc. Fabio Ercoli
Kimmo Sivonen, JuhoHaatanen, Pasi Laulumaa
Finnish Game and Fisheries ResearchInstituteMarkku PursiainenSimo Jalli
Maj & Tor Nessling Foundation
Finnish Game and Fisheries Research Institute
Biological interactions Graduate School
Shareholder associations in Lake Päijänne& Saimaa
Crayfish researchprogram 2005-2012
Thank you!