CHANGES IN SUBSTRATE, MORPHOLOGY, AND SMALLMOUTH BASS AND WALLEYE POTENTIAL SPAWNING HABITAT -- TWO YEARS AFTER THE REMOVAL OF THE ST. JOHN'S DAM, SANDUSKY RIVER, OHIO

Documenting ecosystem improvement after dam removal is integral to obtaining mitigation credit for river restoration. To document the effects of the November 2003 removal of the St. John's dam, substrate and morphology were mapped along the Mexico Bridge Reach, 7 – 9 miles upstream. Geographically referenced field data were collected in Summer 2003, Fall 2004, and Summer 2005. Combining preferred substrates (boulder, cobble, and gravel) with preferred morphology (runs and glides) in GIS derived potential spawning habitat for each year. Substrate changes occur more rapidly than morphological changes, driving change in spawning habitat. Preliminary findings of pre- and post-dam removal surveys show the following: 1) substrate consisting of boulder and cobble comprised 1% of the substrates and remained essentially constant over the three-year study; 2) cobble and gravel substrate, increased from 30% of the available acreage in 2003 to 47% in 2004, but then decreased to 26% in 2005; 3) sand and mud substrate decreased from 69% in 2003 to 53% in 2004, but increased to 73% in 2005. Boulder, cobble and gravel, the prime spawning substrates, moved through this reach in 2004 and was most likely transported downstream in 2005. This accounts for a relative increase in sand and mud in 2005. These surveys document redistribution of potential spawning habitat for smallmouth bass and walleye after dam removal. These habitat changes along with hydrodynamic modeling, macroinvertebrate sampling, and fish sampling performed by collaborators will help establish the evolution of ecosystem restoration after dam removal, possibly indicating that one year of post-removal monitoring is insufficient to characterize ecosystem improvement along a single reach.