Location: Kentucky Lake, TN Colvin, M.E. G.D. Scholten, and P.W. Bettoli. 2013. Predicting paddlefish roe yields using an extension of the Beverton-Holt equilibrium yield model. Submitted to North American Journal of Fisheries Management. North American Journal of Fisheries Management. 33(5): 940-949. Here

Overview.— Equilibrium yield models predict the total biomass removed from an exploited stock; however traditional yield models cannot be used when a fishery targets ovarian tissue for caviar because a simple linear relationship between age (or length) and ovary weight does not typically exist. We extended the traditional Beverton-Holt equilibrium yield model to predict roe yields of paddlefish Polyodon spathula in Kentucky Lake, Tennessee-Kentucky, as a function of varying conditional fishing mortality rates (0.1 to 0.7), conditional natural mortality rates (9 and 18%), and four minimum size limits ranging from 864 mm eye-fork length (EFL) to 1,016 mm EFL. These results were then compared to a traditional biomass-based yield assessment. Analysis of roe yields indicated the potential for growth overfishing at lower exploitation rates and minimum length limits than the biomass-based assessment. Additionally, biomass-based yields were sensitive to an increase in natural mortality, while roe yield patterns were similar regardless of the natural mortality rate simulated. These results indicated that higher minimum length limits would increase roe yield and reduce the potential for growth and recruitment overfishing at the natural mortality rates simulated. Biomass-based equilibrium yield assessments are commonly used to assess the effects of harvest on caviar-producing Acipenseriformes; however, our analysis demonstrates that such assessments likely underestimate the potential for and severity of growth overfishing when ovarian tissue is targeted. Therefore, equilibrium roe yield-per-recruit models should also be considered to guide the management process.