Effects of environmental hypoxia on population characteristics of red swamp crayfish Procambarus clarkii in the Atchafalaya River Basin, Louisiana

Abstract

Spatial and temporal heterogeneity in Atchafalaya River Basin (ARB) physical and chemical characteristics are associated with floodplain inundation and rising water temperatures, resulting in extensive areas of the ARB that experience hypoxia (dissolved oxygen [DO] ≤2.0 mg/L) for several weeks to months throughout the annual flood pulse. Although red swamp crayfish Procambarus clarkii can tolerate relatively low DO concentrations, effects of chronic hypoxic exposure on wild populations have not been extensively studied. Here we compare population characteristics of P. clarkii from normoxic and chronically hypoxic locations in the southeastern ARB that were sampled semi-monthly during the 2008 and 2009 crayfish harvest periods. Carapace length and catch per unit effort (CPUE) of P. clarkii from normoxic and hypoxic locations were similar prior to hypoxia development during both sample years. Hypoxia developed when mean water temperature reached 20°C, and diurnal DO concentrations at hypoxic locations remained below 2.0 mg/L on every sample date during the period of environmental hypoxia. During this period in both sample years, P. clarkii at hypoxic locations had a significantly smaller mean carapace length and mean CPUE was lower on every sample date.