Population viability analyses for three Macrhybopsis spp. of the Lower Missouri River

Abstract

Recent declines in three species of chubs that inhabit the lower Missouri River (shoal chub M. hyostoma , sicklefin chub M. meeki and sturgeon chub M. gelida ) have become a concern in the management of their own populations and the endangered pallid sturgeon ( Scaphirhynchus albus ) that feeds on them. These chub populations encounter threats from fish predation and habitat loss. With the recent advancements in the understanding of the reproductive life history of these species, their declines have prompted development of population models and population viability analyses. For each species, we developed an age‐structured population matrix model with hierarchical stochasticity, which partitions parameter total variance into sampling and temporal components. Using these models, we found population growth rate of all three chub species decreased when stochasticity was added to the model. While examining sensitivity, we found individual fish growth, as measured by length‐at‐age, to impact population growth rate and depending on the species, could be up to four times more influential than overall survival, the next most sensitive parameter. Current survival rates have large temporal variance; more research into accuracy and factors that influence survival rates is needed.