Using a temperature-dependent population model to predict the population growth rates of grass carp across North America

Invasion risk and impact are related to the population growth rate of newly introduced species. We parameterized a temperature dependent age- and size-structured integral projection model (IPM) to predict the population growth rate of invasive grass carp (Ctenopharyngodon idella) in North America. We formulated models using available data on temperature dependence in the age at maturity and fecundity for grass carp and found a small increase in population growth rate at higher temperatures. However, these models did not include potential temperature-dependence in other life history variables (e.g., somatic growth rate, maximum size, and survival) for which there is no data specific to grass carp. Inclusion of simulated temperature dependence in these important variables can reverse the trend in population growth rate and temperature, depending on which combination of life history traits are temperature-dependent. Elasticity analysis highlighted adult survival as a good management target to keep population growth rates small in all cases. We suggest that future studies regarding climate impacts on population growth will require detailed study of the impacts of temperature dependence on various life history traits in order to reach robust conclusions.