US Long-Term Ecological Research Network

How do lake levels affect invaded ecosystems in northern Wisconsin?

Lake levels in northern Wisconsin are currently at historic lows, and climate models predict this trend to continue.  Lowered lake levels affect littoral habitats and associated communities; however specific effects on native and invasive species are poorly understood. I conducted a time series analysis evaluating the relationships between water level, rusty crayfish, and native fishes over 28 years in Sparkling Lake.

Results to date:

  • I found a positive relationship between lake level and rusty crayfish abundance, mediated by the correlation of lake level with cobble habitat that is important for young-of -year crayfish survival. 
  • A reciprocal relationship existed between rusty crayfish and Lepomis spp., where the adults of each group negatively affect the juveniles of the other. 
  • I used parameters estimated from this time series analysis in a stochastic simulation model to predict how rusty crayfish and Lepomis will respond to scenarios of future water level change.  Rusty crayfish are predicted to remain at low abundance in Sparkling Lake under a range of lake level scenarios. 
  • Rusty crayfish abundance is highly sensitive to Lepomis abundance, indicating that it may be important to protect Lepomis from angling mortality to maintain low densities of rusty crayfish, particularly if lake level increases.