Using a stratified-random sampling design, we sampled sauger (Stizoste
dion canadense) by day and night electrofishing during the spring from
Lewis and Clark Reservoir, South Dakota-Nebraska. Catch per unit effo
rt (number of stock-length (greater than or equal to 20 cm) sauger cau
ght per hour of electrofishing) did not vary among three sites (lake,
transition area, and river; P=0.64) nor between diel periods (P=0.91).
Size structure of samples, indexed using stock density indices, was c
onsistently higher during the day than at night; sauger greater than o
r equal to 51 cm were only collected during the day. Differential size
structure for samples collected during diel periods should be conside
red when biologists design sampling programs or assess population size
structure.