Since 2005, spring hatched young-of-year (YOY) small-mouth bass in Pennsylvania reaches of the Susquehanna River have experienced above-normal mortality when summertime streamflows are near or lower than normal. Stress factors include, but are not limited to, low dissolved oxygen and elevated water temperatures during times critical for survival and development (critical period is May 1 through July 31). At this time (2010), widespread disease and mortality are believed to be more prevalent for YOY smallmouth bass in the Susquehanna River Basin than in the Delaware or Allegheny River Basins.