AUTHORS: Juliana Kaloczi, Iowa State University; Michael J Moore, U.S Geological Survey, Iowa Cooperative Fish and Wildlife Research Unit and Iowa State University; Martin Hamel, University of Georgia; Gene Jones, Iowa Department of Natural Resources; Ryan Hupfeld, Iowa Department of Natural Resources, Rebecca Krogman, Iowa Department of Natural Resources.
ABSTRACT: Globally, sturgeon populations have declined due to overharvest for caviar and habitat fragmentation due to dam construction that impairs water quality and disrupts spawning migrations. North American species have had harvest restrictions enacted to recover populations. While similar life history characteristics make Shovelnose Sturgeon vulnerable to many of these same stressors, populations in the Mississippi River basin still support limited commercial and recreational fisheries for roe and meat - conferring the species’ economic, recreational, and cultural importance. Enacting harvest regulations, such as minimum length limits, ensures sustainable harvest and requires knowledge of dynamic rates such as age-specific growth rates. However, the Shovelnose Sturgeon’s long life span and slow growth make estimating these parameters notoriously difficult with traditional methods that rely on annuli counts on bony structures. As a result, there is a lack of reliable growth rates for this species across its range. Therefore, we used an 18-year mark-recapture dataset for Shovelnose Sturgeon collected by the Iowa Department of Natural Resources in the Cedar River at Palisades-Kepler State Park to evaluate incremental growth models for Shovelnose Sturgeon. The Fabens modification of the Von Bertalanffy growth function was used within a Bayesian framework to determine how growth rates vary within the population. Additionally, bomb-radiocarbon age estimates were used to inform a second model within the Bayesian framework to assess how the incorporation of previous knowledge may improve the model. Age estimates and growth rates can be used in population simulations to evaluate sensitivity to harvest under harvest regulations and can inform management across the species’ range.
