A laboratory study was conducted at the Northern Appalachian Research Laboratory (Wellsboro, PA) on the ability to manipulate photoperiod and water temperatures to determine its effects on Eastern elliptio freshwater mussel glochidia production. Brooding mussels were collected from Pine Creek, Tioga County, PA in late December and were housed in the laboratory in groups subjected to one of four environmental treatments: natural temperature and photoperiod, 6 week delay in natural conditions, 12 week delay in natural conditions, and natural temperature and photoperiod with a winter low of 10°C. In this study, "natural" conditions refer to light and temperature conditions that mimic what mussels would have been exposed to at their field collection site. Reproductive activity, including the production of mature and immature glochidia was monitored for 1 year (February 1995 - February 1996) while mussels were housed in the laboratory under their designated experimental treatments. Changes in mussel weight, length, and overall survival was also monitored.