One of the most persistent challenges in walleye larviculture is the high rate of unobserved mortality occurring within the first 30 days post-hatch. Walleye larviculture is characterized by high mortality rates, but oftentimes only a fraction of the total mortality in walleye larviculture is observed. Unobserved mortality is frequently attributed to a high rate of cannibalism at the early life stage. Additionally, dead fry decompose quickly at this stage, which may also contribute towards unaccounted mortality. Despite cannibalism and fry decomposition being frequently identified as causes of unobserved mortality, there is little empirical evidence available that assesses the causes and timeframe of unobserved mortality in walleye larviculture. To further investigate the quantity of unobserved mortality rates, fish survival was determined after three different time periods in the treatment tanks. Larval fry were stocked at low densities of 4-6 fry per liter and raised at optimal conditions for walleye including turbid water, 24-hour feeding, dim lighting and spray bars. In the treatments fry were reared for 8, 15 and 30 days. Tanks were cleaned daily, and dead fry were enumerated to account for observed mortality. At the end of the study period, the tanks were drained and all fry were hand counted. A high rate of unobserved mortality occurred in all treatments. Unobserved mortality averaged 37.62%, 41.15%, and 24.60% of all mortalities from the treatments, respectively.