Population Characteristics of Gizzard Shad Introduced into a Small Western Oklahoma Impoundment

Abstract

Gizzard Shad (Dorosoma cepedianum) are often considered a vital forage species in many aquatic systems. However, when populations of Gizzard Shad become dominated by large (>200 mm) overabundant individuals they can have negative direct and indirect effects on sportfish populations. In September 2016, 198 Gizzard Shad were collected from Lake Carl Etling in farnorthwest Oklahoma to evaluate population characteristics. Total length (TL; mm) and weight (g) were recorded and sagittal otoliths were removed for aging. Gizzard Shad ranged from 56-308 mm TL with a mean age estimated at 2.63 years and a maximum age of 12 years. This Gizzard Shad population has rapid growth rates within the first year, slowing with increasing age, poor relative body condition, low mortality, and is comprised primarily of small adults. We speculate that the fast growth rate of the Gizzard Shad population may be affecting the sportfish populations in Lake Carl Etling, as indicated by low proportional size distribution (PSD) and below average relative weight (Wr) of Walleye (Sander vitreus) and Largemouth Bass (Micropterus salmoides). Information about Gizzard Shad populations in Oklahoma is limited, and this study provides baseline  characteristics to which other Gizzard Shad populations in small impoundments can be compared.