IMPROVING THE EFFECTIVENESS OF SIMPLE CRYOPRESERVATION TECHNIQUES ON SPERM OF YELLOW PERCH Perca flavescens

Sperm motility of two different age classes (0+ and 3+) of Yellow Perch, efficiency of two freezing methods, the pellet method (Ciereszko et al.,1993) and the Draper method (Draper and Moens, 2009) utilizing two different cryoprotectants (DMSO and methanol), and the viability of progenies obtained from fertilization using cryopreserved sperm were examined through a series of experiments. The first experiment addressed comparison of motility of fresh sperm and pellet method cryopreserved sperm. Despite high motility of fresh sperm, 75% and 100%, of 0+ and 3+ males respectively, post thaw motility of seminal plasma devoid cryopreserved sperm was 0%. The second experiment addressed the efficiency of the two freezing methods, pellet and Draper, with DMSO and methanol in addition to salmon seminal plasma, utilizing 0+ Yellow Perch fresh sperm with 100% initial motility. Cryopreserved sperm was thawed and motility measured for both methods in the presence and absence of sperm extender solution. Sperm motility was not significantly different between the pellet (13.3+10.4%) and Draper (10.3+12.9%) methods in the absence of extender; however, motility of the pellet method sperm was further improved (20+8.7%) by the addition of sperm extender during thawing while motility of Draper method sperm (10+7.1%) was not. Cryopreserved sperm from experiment 2 was further evaluated based on fertilization rate and ultimate survival and growth of larvae and juveniles up to 14 days post hatch.

The third and fourth experiments examined the effect of ultraviolet (UV) exposure on fresh sperm and sperm cryopreserved with the pellet method following the UV irradiation procedure of Garcia-Abiado et al. (2001).  As control, fresh sperm and cryopreserved sperm were subjected to the same treatment as UV-irradiated sperm but without UV exposure.  Motility of both control and UV exposed fresh sperm decreased from 75% to 50% following treatment.  Motility of control and UV exposed sperm cryopreserved with DMSO and control sperm cryopreserved with methanol decreased from 100% fresh motility to 75% following cryopreservation, while UV exposed sperm cryopreserved with methanol decreased from 100% fresh motility to 50% following cryopreservation. This experimentation provides significant new data to improve the effectiveness of simple cryopreservation techniques for Yellow Perch.