Habitat Fragmentation and Barrier Types

Making the Most of What We Have:

• Much of Wisconsin’s desirable aquatic habitat has been lost or significantly altered. Artificial aquatic habitat is expensive to create and is often inferior to quality natural habitat. Many pockets of quality aquatic habitat remain, but are ecologically isolated.
• The Ozaukee County inventory demonstrates much ecologically significant, but isolated, habitat throughout the county.
• Reconnecting isolated habitat restores its function to the watershed.

Barrier Types

• A barrier prevents migration of aquatic organisms. They do not affect all organisms equally, and may not necessarily be effective throughout the year.  
• Impediments directly resulting from human activities include:  
  • Dams 
  • Improperly designed/installed culverts 
  • Excessive water velocities and insufficient refuge in “improved” stream reaches 
  • Previous fill deposits 
  • Artificially lined channels 
  • Channel-constricting bridge abutments 

• Impediments indirectly resulting from human actions include:  
  • Intensified sediment accretion and debris accumulation 
  • Entrenchment resulting from channelization and development 
  • Channel dispersion related to dense invasive vegetation 
  • Compromised hydrology 

• Naturally occurring barriers include:
  • Some debris jams and sediment accretions
  • Some high-gradient reaches
  • Ephemeral and losing streams
  • Natural channel dispersion in wetlands