The Columbus Zoo and Aquarium has announced a leadership change. The zoo's board of directors accepted the resignation of President and CEO Dale Schmidt, who announced his immediate departure for personal reasons. Schmidt took over following the death of Jeff Swanagan in 2009. Schmidt says in a statement that the zoo completed a difficult transition, set revenue and attendance records, weathered a national crisis and opened an award-winning exhibit during his time. Tom Stalf - who joined the Columbus Zoo in 2010 -- has been named interim president. The board says it will announce plans at a later date regarding a search for a permanent replacement.