Effects of flow regime on growth rate in freshwater drum, Aplodinotus grunniens

Abstract

Understanding the influence of flow regime hydrology on fish life history is essential for conserva- tion and management of lotic ecosystems. The objec- tives of this study were to investigate growth patterns of Wabash River freshwater drum Aplodinotus grunniens relativetoage,sex,and longtermflowregimevariation. Growth was estimated using back-calculated lengths from otolith measurements. Flow regime was described using Indicators of Hydrologic Alteration flow metrics calculated from long-term stream flow data at USGS stations. A generalized linear mixed model was used to modelgrowthasafunctionofage,sex,andflowregime. Freshwater drum growth was explained by variation in age, sex, and flow magnitude. Freshwater drum exhib- ited indeterminate growth relative to age. Mean growth rates and mean length at age were lower in males than females. High magnitude flow events were positively correlated with increased growth rates in both males and females. However, the effect of flow magnitude variation on growth was stronger in males. The primary flow regime metrics related to growth were magnitude- based and were not related to timing offlow events. The study provides evidence that long term variation in flow regime is a catalyst for alterations in freshwater drum growth rates.