Ecological impacts of invasive signalcrayfish in large boreal lakes

Timo RuokonenPyhäjärvi Institute / University of Jyväskylä

timo.ruokonen@pji.fi

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!