Population Characteristics of Gizzard Shad in Missouri Reservoirs and Their Relation to Reservoir Productivity, Mean Depth, and Sport Fish Growth

Abstract

Population characteristics of gizzard shad Dorosoma cepedianum were examined in 14 Missouri reservoirs to determine if they were related to reservoir productivity (chlorophyll-a concentrations, mg/m3, CHLA), mean depth, and sport fish growth. Gizzard shad catch per unit effort (CPUE, >age 1), mean length at age 1, mortality, and a recruitment variability index (RVI, larger numbers indicate more consistent recruitment) increased with increasing reservoir productivity and decreasing mean depth, while proportional stock density (PSD), relative weight (Wr), and mean length at age 3 decreased. In stepwise regression models, gizzard shad mean length at age 1 was negatively related to mean depth; mean length at age 3 was negatively related to CHLA; mortality was negatively related to mean depth and positively related to CPUE; and RVI was negatively related to PSD and positively related to mean length at age 1. Mean lengths at age 3 for largemouth bass Micropterus salmoides and white crappie Pomoxis annularis (used as indicator of growth) were negatively related to gizzard shad mean length at age 1. Sport fish grew faster in deep, less-productive reservoirs, in which gizzard shad grew more slowly during their first year, than they did in shallow, more-productive reservoirs, in which gizzard shad grew faster.