Use of a Restrictive Regulation to Manage Walleyes in a New Glacial Lake in South Dakota

Abstract

AbstractAbove‐average precipitation in the 1990s resulted in many new fisheries across northeastern South Dakota and elsewhere in the Upper Midwest. Walleye Sander vitreus populations in these new fisheries can be extremely vulnerable to angler harvest. In an attempt to maintain a Walleye fishery in Reetz Lake, South Dakota, a new lake, a restrictive regulation of one Walleye ≥711 mm TL per day was implemented when the lake opened to public fishing (October 2001). To evaluate the regulation, we monitored the estimated number of Walleyes ≥508 mm, Walleye gill‐net catch per unit of effort (CPUE) of stock‐length fish (≥250 mm), size structure, condition, length at age at capture (ages 2–5), mortality, recruitment, and angler use during the period 2001–2019. The estimated number of Wall‐eyes ≥508 mm, gill‐net CPUE, and proportional size distribution of preferred‐length fish (PSD‐P; ≥510 mm) trended higher across years. Relative weight (Wr) for the quality–preferred (380–509 mm) and preferred–memorable (510–629 mm) length‐groups and the length at age at capture for ages 4 and 5 trended lower. Walleyes <510 mm were in better condition than larger fish throughout the study. Estimated total mortality was 62% in 2004 but substantially declined in subsequent years before ranging from 6% to 21% for 2010–2019. The coefficient of variation of age‐3 gill‐net CPUE by cohort was 93%, indicating variable recruitment. Decreasing trends in Wr and growth were not surprising, as Walleye CPUE increased through time. Lengths at age remained at or above statewide and national averages. The values for number of angler‐hours and Walleye catch rates were high during the summer months when most anglers targeted Walleye. The regulation that restricted harvest at Reetz Lake to one Walleye ≥711 mm allowed an abundant Walleye population to establish and was successful at maintaining the fishery in terms of abundance, size structure, and angler use.