Historical Biogeography and Not Stocking Is the Better Predictor of Black Bass Species Composition in Louisiana Gulf Slope and Lower Mississippi Valley Streams

Spotted Bass (Micropterus punctulatus) and Largemouth Bass (Micropterus salmoides salmoides) are often dominant aquatic predators in the southeastern U.S.  Since 2008, we have conducted surveys employing a standardized sampling methodology in 83 Louisiana wadeable streams.  Herein, we present a retrospective analysis of black bass distributions among drainages and relationships with stream habitat characteristics. We also examine the hypothesis that Florida Largemouth Bass (Micropterus salmoides floridanus) stockings in nearby lakes have influenced bass distribution and abundance.  We analyzed catch-per-unit effort (CPUE) of Spotted Bass and Largemouth Bass by generalized linear mixed models including major drainages, habitat characteristics, and stocking of Largemouth Bass as explanatory variables.  Spotted Bass CPUE was highest in drainages east of, but disconnected from the Mississippi River, Largemouth Bass CPUE was highest in the Ouachita River basin and direct Mississippi River tributary drainages.  Spotted Bass CPUE was best explained by positive associations with current velocity and dissolved oxygen, and to a lesser extent, a negative association with Largemouth Bass stocking.  Largemouth Bass CPUE was best explained by positive associations with silty substrates and woody debris.  These data suggest that conservation and management of Spotted Bass need to consider the impacts of Largemouth Bass stocking programs in connected systems.