Gizzard Shad Recruitment Patterns in a Western South Dakota Irrigation Reservoir

ABSTRACT

Gizzard shad (Dorosoma cepedianum) is a primary prey species in Angostura Reservoir, South Dakota, which is on the northwestern edge of the shad range. The primary objective of this study was to determine the extent to which winter severity influences gizzard shad recruitment patterns in this reservoir. Adult gizzard shad were collected during spring electrofishing, and sagittal otoliths were removed and aged. Gizzard shad recruitment was inconsistent, with only age-3, aged, and age-10 individuals present in a sample of 100 adults. However, gizzard shad recruitment was not exclusively regulated by winter temperatures in this South Dakota impoundment. Rather, a combination of biotic (e.g., age-0 gizzard shad abundance) and abiotic (e.g., winter duration) factors apparently interact to regulate recruitment. Juvenile gizzard shad were most likely to recruit into the adult population in years exhibiting low age-0 shad abundance, warmer summer temperatures, and warmer winters.