Evaluation of a 23-cm Minimum Length Limit for Black and White Crappies in a Small South Dakota Impoundment

Abstract

The South Dakota Department of Game, Fish, and Parks instituted a 23-cm minimum length limit for black crappie Pomoxis nigromaculatus and white crappie P. annularis in Lake Alvin on 1 January 1996 because an undesirable size and age structure indicated that these populations were being overharvested. Crappies were sampled annually using trap (modified fyke) nets from 1992 to 1999. Mean catch per unit effort (fish/net night) was higher in the postregulation years (1996–1999) than in the preregulation years (1992–1995) for both species. The mean length of age-3 fish in the postregulation years was not different from that of the 1995 baseline for either species. The relative stock density of 23-cm crappies did not increase after implementation of the length limit. Limited prey availability, which was inferred from the negative trend of relative weight with respect to length, was the likely reason that larger crappies did not appear. The 23-cm minimum length limit was removed on 1 January 2000 to give anglers the opportunity to harvest smaller crappies.