Sensitivity of Lake Sturgeon Population Dynamics and Genetics to Demographic Parameters

Uncertainty in population parameters can make managing fisheries difficult, especially for long-lived species such as lake sturgeon Acipenser fulvescens. Models can be used to explore population parameter uncertainty and how uncertainty affects demographic and genetic population outputs through the use of sensitivity analyses. The objective of this study was to determine which lake sturgeon population parameters have the greatest influence on demographic characteristics, including rates of extinction and percentage of populations increasing from their initial size, and population genetic characteristics, including percentage of unique alleles retained and average inbreeding coefficient. An individual-based modeling approach that represented demographic and genetic processes was used to achieve this objective. Individual lake sturgeon were tracked throughout the modeling process with unique identifiers, allowing for the determination of the degree of inbreeding and the number of unique alleles retained. Sensitivity analyses were performed by changing one parameter at a time across a range of plausible values while holding all of the other parameters at their nominal values. All responses were hypersensitive to young-of-the-year mortality, post-young-of-the-year mortality, age at first maturation for females, and probability of mating for females. The post-young-of-the-year mortality rate was the most sensitive of all of the population parameters. The outputs were relatively insensitive to changes in the age at first maturation for males and the probability of mating for males. Sensitivity was dependent upon the initial population size, with population parameters having differing sensitivities with respect to other parameters for smaller and larger population sizes. The demographic and genetic outputs were related to one another via similar relationships for each of the population sizes. These analyses should be used to target rehabilitation efforts on altering population parameters with the largest influence on population persistence and genetic integrity.