Identifying Sampling Methods to Reliably Index Spring Age-1 Walleye Relative Abundance in South Dakota Natural Lakes

Walleye Sander vitreus are the most popular species among South Dakota anglers, and many lakes are stocked to maintain or supplement populations. Limited work in assessing survival of juvenile walleye in South Dakota had been completed due to difficulties in sampling age-1 individuals.  An assessment of age-1 walleye immediately after the first winter of life could aid in prioritizing walleye stocking schedules each year. To identify sampling methods to reliably index spring age-1 walleye relative abundance, sampling was conducted weekly for one month in four eastern South Dakota lakes.  Four sampling gears (benthic sled, near-shore electrofishing, nearshore and offshore gill nets, and mini fyke nets) were tested to determine which gear is most appropriate for sampling age-1 walleye in the spring.  Catch per unit effort (CPUE) and time required to deploy each gear was used to compare efficiencies of each gear.  Sampling precision was estimated using coefficients of variation and a power analysis was used to estimate sample sizes required to detect a 25% change in mean walleye CPUE for each gear.  Identification of the most appropriate sampling gear for spring age-1 walleye may help to develop a standardized method for assessing year-class strength and recruitment in South Dakota waters.