The Effect of Sediment Cover and Female Characteristics on the Hatching Success of Walleye

Natural and anthropogenic sources of sedimentation have the potential to degrade spawning habitat and negatively affect incubating fish embryos. Walleye Sander vitreus are lithophilic broadcast spawners that use specific spawning habitats that are vulnerable to degradation caused by deposition of suspended sediments. We measured the effect of different types of sediment cover on hatching success of Walleye eggs and assessed whether differences in female Walleye (female length and mean egg size) account for tolerance to sediment cover. Experiments were carried out in 2018 to test the effect of sediment cover on hatching success and in 2019 to test how female identity and female length or mean egg size may interact with sediment cover to influence hatching success. Eggs in both experiments were exposed to instantaneous sediment cover (0-7 mm) of either sand or silt from fertilization until day 15 of incubation. Results indicated that Walleye eggs were sensitive to silt cover (71% mortality with 2 mm of silt cover) but not sand cover (47% mortality with 7 mm of sand cover). Hatching success differed significantly among individual females. Although there was an indication that hatching success was marginally negatively related to female length and positively related to mean egg size, sediment cover seemed to have similar effects on eggs, regardless of female length or egg size. Susceptibility of Walleye eggs to mortality caused by sediment cover further underscores the need to limit large-scale sediment loading and resuspension in aquatic systems.