HARVEST OF SHOVELNOSE STURGEON INFLUENCES YEAR CLASS 
STRENGTH AND ADULT ABUNDANCE:  ARE WE MOVING TOWARDS 
COLLAPSE?

Robert E. Colombo1,2, James E. Garvey1,2, David P. Herzog3, Robert A. Hrabik3, and  
Neal D. Jackson1,2
1Department of Zoology, Southern Illinois University, Carbondale, IL 62901.  2Fisheries 
and Illinois Aquaculture Center, Southern Illinois University, Carbondale, IL 62901.  
3Missouri Department of Conservation, Resource Science Division, Open Rivers and 
Wetlands Field Station, 3815 East Jackson Boulevard, Jackson, MO 63755

	The collapse of caviar fisheries in the Volga River and Caspian Sea, has increased 
demand for domestic caviar, thereby increasing harvest of shovelnose sturgeon in the 
Middle Mississippi River (MMR).  Currently, harvest impacts are unknown.  We 
sampled density and age structure of shovelnose sturgeon in the MMR during 2000, 
2002, and 2004 to determine the impact of harvest on this population.  Simulation 
modeling assessed how different length limits affected population yield and reproductive 
potential.  Annual mortality for MMR shovelnose sturgeon was higher than previously 
published mortality rates for this species.  Both adult density (P < 0.001) and recruitment 
strength (2000, P < 0.05; 2001, P < 0.05; 2003, P < 0.05) declined with harvest. 
Simulation modeling suggested that under the current level of harvest with no minimum 
length limit or the proposed minimum length limit (609 mm), the population of 
shovelnose sturgeon in the MMR would experience unsustainable growth and recruitment 
overfishing.  If a more conservative length limit (650 mm) was imposed, the shovelnose 
sturgeon fishery in the MMR could withstand an increase in harvest.  Commercial 
exploitation is negatively affecting the shovelnose sturgeon population in the MMR, 
potentially causing a collapse of the fishery if not addressed.

Key Words:  shovelnose sturgeon, Mississippi River, harvest, year class strength, 
simulation modeling