Quantifying quality attributes of walleye eggs prior to fertilization—Impact of time of ovulation and gametes storage

Abstract

This study addressed the over-ripening process of walleye eggs that is critical during gamete collection and artificial propagation. We evaluated the quality of eggs (1) stored for varying periods of time, (2) supplemented with Moore's extender or (3) stored with added infertile “large” eggs prior to fertilization. Three separate experiments were carried out at three different egg collection periods. We sought to determine the biochemical indicators of the fertilizing ability of eggs and the changes in these indicators during over-ripening. Our results showed that survival rate at eyed stage embryo decreased from 73% to 21% when the duration of storage increased from 8 to 42h. Extended time of storage caused eggs to release higher amounts of protein and survival rate correlated inversely with the concentration of protein released into the ovarian fluid (P<0.05). Survival rates decreased with the presence of infertile “large” eggs in both cases (P<0.01). The amount of ovarian fluid positively influenced egg viability after 42h storage (P<0.01). Eggs stored in Moore's extender survived better than those stored without extender (P<0.05). Survival of embryos decreased with the addition of infertile eggs (P=0.05). In all experiments protein concentration increased with increasing storage period and resulted in increasing turbidity of ovarian fluid. Our results indicated that protein concentration and turbidity of ovarian fluid can be used as indicators to evaluate the fertilizing ability of walleye eggs. It is also suggested that walleye eggs be stored in an extender to decrease the negative effect of over-ripening on egg viability.