Seasonal sampling dynamics of smallmouth bass (Micropterus dolomieu) in northeastern South Dakota

Numerous studies on smallmouth bass (Micropterus dolomieu) have focused on movements, diets, and capture rates among habitat types, but we are aware of no study that has documented capture rates and size structure by month to aid in assessment and management of this fish. The objective of this study was to determine monthly sampling dynamics and population size structure of smallmouth bass in four northeastern South Dakota glacial lakes. Smallmouth bass were collected monthly (May-September) from Enemy Swim Lake and Roy Lake in 2007 and Clear Lake and Pickerel Lake in 2008 using modified-fyke nets and night electrofishing in rocky habitats. Monthly mean catch-per-unit-effort (CPUE) values for smallmouth bass collected with fyke nets were variable but generally low (0.2-4.7 fish/net night) across months and lakes. Monthly mean CPUE values for smallmouth bass collected by electrofishing were variable in all four lakes (99.7-771.8 fish/h); however, in Clear Lake and Enemy Swim Lake CPUE significantly increased from May through September, primarily due to age-0 bass becoming vulnerable to electrofishing. For all lakes except Clear Lake, there were no significant differences in monthly mean CPUE values of 180mm and longer smallmouth bass. Length distributions varied by month, but in general May and June samples contained a higher proportion of larger individuals than later sampling months. Overall mean relative weight (Wr) values were greater than 80, but relative weight varied among lakes and months. Our results suggest that spring (May to June) sampling of smallmouth bass using night electrofishing in rocky habitats will result in the broadest length range of captured bass.