Analysis of Factors Influencing Rock Bass Population Dynamics in an Ozark Border Stream

There has been an increasing interest in the management of rock bass (Ambloplites rupestris) in Missouri Ozark streams since the 1980’s.  Intensive management of rock bass in the Meramec River started when biologists observed increased mortality, decreased size structure, and few fish >200mm, and angler surveys suggested overexploitation.  The Missouri Department of Conservation initiated a 200mm minimum length limit on Meramec River rock bass in 2008.  Our objectives were to determine if rock bass abundance, size structure, growth, and mortality differed after the implementation of the minimum length limit.  We also explored the influence of river discharge on year-class strength and recruitment.  Rock bass abundance, growth and mortality did not differ before (2002-2005) and after (2010-2012) the minimum length limit regulation. However,  year class strength decreased with increased high mean annual river flows, and decreased with  greater variability in mean spring and fall flows, suggesting environmental factors such as river flows and recruitment may be affecting the utility of the length limit.  Future rock bass management may need to consider the relationship between river flows, recruitment, and length limits.