Frankel, Tyler EdwardSeveral studies have attempted to determine the optimal freezing rate for the cryopreservation of striped bass spermatozoa. In this study, the effects of freezing rate (-10, -15, -20 and -40<super>o</super>C/min) on sperm quality was examined utilizing Sybr-14/Propidium Iodide staining to confirm membrane integrity, a luciferin-luciferase assay to estimate ATP concentration and a Hamilton-Thorne CEROS^TM system to characterize sperm motion. Males (n=12) were sampled once a week for five weeks. Samples were extended, cryo-protected using a 7.5% (v/v) dimethyl sulfoxide solution, and frozen using a controlled-rate freezer. Samples were stored in liquid nitrogen for 49 days and re-evaluated post-thaw. Sperm cryopreserved at -40<super>o</super>C per minute resulted in: total motility (10.06%), progressive motility (7.14%), ATP concentration (0.86 pmol/million cells), and sperm viability (56.5%); which were greater (P < 0.05) than the slower rates. Results demonstrate that -40<super>o</super>C/minute was the optimal freezing rate among those tested for the cryopreservation of striped bass spermatozoa.ThesisAnimal sciencesFisheries and aquatic sciencesPhysiologyATPCASAFreezing RateStriped bassViability