Comparison of Walleye Egg Survival Following Fertilization at Differing Egg Depths

Extruded egg depth during artificial fertilization of walleye Sander vitreus is known to affect egg fertility and has been suspected of contributing to the observed low percent hatch of eggs in South Dakota. Our objective of this study was to determine if walleye egg survival through hatching could be improved by reducing the egg depth in standard pans during fertilization. Survival of walleye eggs extruded to the currently-used depth of 19 mm was compared to a reduced depth of 7 mm in standard pans and fertilized with equal amounts (9 ml) of extended semen. Eggs were collected and fertilized during 3 days of each spawning season in 2017 and 2018. Egg survival through hatching was significantly (P<0.01) greater at the 7 mm depth during 4 of 6 days; there was no difference in egg survival between egg depths during the other 2 days, both occurred in 2017. Our results indicate that reduced egg depth during fertilization will enhance egg survival. The improved survival at the 7-mm depth likely was due to increased fertility resulting from an increased ratio of semen to egg. Although egg survival was higher at the 7-mm depth versus the 19-mm depth, the survival (13 – 59%) from each egg taking day was lower than commonly reported (>65%) in other states. The lower egg survival South Dakota has experienced suggest that factors other than egg depth may also be hindering fertilization and should be investigated.