Onion River Restoration Project

Steve Schubert volunteers with the Lakeside Chapter of Trout Unlimited (TU) in Sheboygan, Wisconsin to restore the upper reaches of the Onion River. This is an ongoing restoration project designed to support a reproducing, wild brown trout population. The original goal was to stabilize the stream banks to reduce erosion from stormwater runoff. This would, in turn, improve benthic habitat for invertebrates that the fishery relies upon. Then around 2008, the highly aggressive emerald ash borer (EAB) was discovered in WI. The EAB is an exotic beetle that has killed hundreds of millions of ash trees across 35 states in North America since 2002.  The Onion River riparian habitat and canopy was primarily a white ash forest (i.e., white ash, sugar maple, basswood, beech, red and white oak). The shade from the trees kept the stream cool.  But as the ash trees succumbed to the EAB they fell alongside and across the stream. Normally, a few fallen trees is okay because they provide variety in habitat complexity, but there were so many dead trees that they created log jams that caused the river to jump its banks during the spring snow melt and subsequent rains. The channel became braided and the habitat for fish became degraded.  TU stepped in and started removing the fallen ash trees and re-stabilizing the stream banks. Today there are still a few standing dead ash trees that provide habitat for cavity nesting species like woodpeckers, bats, flying squirrels, and other small mammals. Later this year, TU will replant native maple, oak, and other wetland species near the stream to jump start the forest regeneration.

Figure 1. Downed and standing dead white ash trees along the Onion River headwaters.

Figure 2. Trout Unlimited chainsaw crews cut and haul dead ash tree logs out of the stream channel.

Figure 3. Wild brown trout from the Onion River.