Comparison of Day and Night Electrofishing to Sample Smallmouth Bass in Natural Lakes of Eastern South Dakota

Smallmouth Bass Micropterus dolomieu , an important sport fish and apex predator, are commonly sampled by fisheries personnel using night electrofishing. We assessed day and night electrofishing catch per hour of effort (CPUE), sampling precision (i.e., CV), and size structure of Smallmouth Bass in eight northeast South Dakota natural lakes during 2013–2016 to determine if day electrofishing was a viable option for population assessment. Night CPUE was generally greater than day CPUE in paired samples. Significant differences in CPUE for fish ≥ 180‐mm TL were identified in approximately one‐third of lake year comparisons. Day and night CPUE were more likely to be significantly different in fish < 350 mm‐TL. A significant linear relationship was identified between day CPUE and night CPUE for all fish. Coefficients of variation of CPUE were similar between day and night samples. Significant differences in proportional size distribution (PSD) were identified for 6 of 15 day–night pairs, but no pattern was identified and no differences in proportional size distribution of preferred‐length fish (PSD‐P) values were found. A linear relationship was identified between day and night PSD and day and night PSD‐P, and neither relationship differed from the 1:1 line. A significant curvilinear relationship was present between the percent deviations (PD) of day and night CPUE across Secchi depths. We believe that day electrofishing can be used to assess Smallmouth Bass populations in eastern South Dakota natural lakes. Received January 9, 2017; accepted July 3, 2017 Published online October 11, 2017