An important component of effective fisheries management is estimating fish ages. Age estimates can be used to estimate recruitment, relative abundance of age‐groups, total mortality, and growth. Because of difficulty in estimating Northern Pike Esox lucius ages using scales and whole cleithra, we compared precision and bias of age estimates from whole cleithra, sectioned cleithra, metapterygoid bones, otoliths, and scales. Metapterygoid bones and sectioned cleithra represent two novel structures for estimating ages in North America, and the assessment of otoliths is limited. Complete agreement and consensus agreement rates were greatest for otoliths, sectioned cleithra, and metapterygoid bones. Otoliths provided the most precise age estimates and whole cleithra were the least precise. Consensus age estimates for sectioned cleithra were lower than whole cleithrum estimates. Consensus age estimates from sectioned otoliths were lower than mean age estimates from scales, sectioned cleithra, and whole cleithra, and y‐intercepts from the age‐bias plots were significantly different than zero. We suggest that otoliths, sectioned cleithra, and metapterygoid bones can be used to estimate Northern Pike ages, but recommend the use of sectioned otoliths because they had the highest precision and otoliths have become a common means of estimating ages for many species. Received December 8, 2015; accepted March 31, 2016 Published online July 20, 2016

We estimated the timing of annulus formation and the relationship between otolith radius length (whole view) and total length (TL) in yellow perch Perca flavescens from South Dakota lakes. Marginal increment analysis indicated that a single opaque band is formed during the summer months and that the timing of annulus formation varies with fish age. The lowest marginal increment measurements (i.e., those suggesting that annulus formation was recently completed) were most likely to occur in July, but at Waubay Lake the lowest increment for some cohorts was observed in August. Fish of age 4 or less were more likely to complete annulus formation during June. Personnel responsible for aging otoliths need to be aware of the differential timing of annulus formation. Significant relationships were observed between yellow perch TL and otolith radius length for 49 populations. Nearly all (98%) of the regression intercepts were negative. Back-calculated TLs were estimated from otolith annulus measurements using the direct proportion method and compared with the TLs previously measured for three populations. The back-calculated TL estimates were similar to the previously observed TLs, suggesting that the direct proportion method can be used to back-calculate TLs from yellow perch otoliths.

Above-normal precipitation in the 1990s resulted in new waters and Walleye Sander vitreus fisheries across northeastern South Dakota. Concerns with overharvest led to the implementation of a Walleye minimum length limit (MLL) on many new fisheries, but over time most of the MLLs were removed. We were interested in knowing why the MLLs failed. We compared Walleye gill-net data and angler creel data under rising and declining water regimes and between periods with and without an MLL regulation in two new waters (Bitter Lake and Waubay Lake). We also assessed Walleye annual recruitment and growth patterns and examined if water regimes, MLLs, or Walleye recruitment were potential drivers of Walleye relative abundance, growth, and size structure. Few differences were found across water regimes and between periods with and without an MLL. At Bitter Lake, significant differences were identified across water regimes for the number of age-3 Walleyes per gill net, Walleye proportional size distribution of preferred length (PSD-P), angling pressure, and angler catch rates of Walleyes. Walleye relative weight and PSD-P significantly differed between water regimes at Waubay Lake. Mean length at capture for age-3 Walleyes and proportional size distribution were significantly different between periods having an MLL and no MLL at Bitter Lake. At Waubay Lake, Walleye gill-net CPUE (number/gill net) and PSD-P significantly differed between periods with and without an MLL. Water regimes, MLL, and Walleye recruitment were not identified as strong drivers of Walleye population characteristics. Recruitment was variable in each lake (Bitter Lake age-3 CPUE CV = 148%, Waubay Lake age-3 CPUE CV = 166%), with occasional strong cohorts recruiting. We believe recruitment dynamics influenced Walleye abundance and growth, which led to the removal of MLLs from each lake. Knowledge concerning Walleye population recruitment dynamics and growth is important when implementing MLLs and evaluating their effectiveness.

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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